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1
Swinnen, Ward, Nils Broothaerts, and Gert Verstraeten. "Modelling long-term alluvial-peatland dynamics in temperate river floodplains." Biogeosciences 18, no. 23 (December 1, 2021): 6181–212. http://dx.doi.org/10.5194/bg-18-6181-2021.
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Abstract. Peat growth is a frequent phenomenon in European river valleys. The presence of peat in the floodplain stratigraphy makes them hotspots of carbon storage. The long-term dynamics of alluvial peatlands are complex due to interactions between the peat and the local river network, and as a result, alluvial-peatland development in relation to both regional and local conditions is not well understood. In this study, a new modelling framework is presented to simulate long-term peatland development in river floodplains by coupling a river basin hydrology model (STREAM – Spatial Tools for River basins and Environment and Analysis of Management options) with a local peat growth model (modified version of DigiBog). The model is applied to two lowland rivers in northern Belgium, located in the European loess (Dijle (Dyle) River) and sand (Grote Nete River) belts. Parameter sensitivity analysis and scenario analysis are used to study the relative importance of internal processes and environmental conditions on peatland development. The simulation results demonstrate that the peat thickness is largely determined by the spacing and mobility of the local river channel(s) rather than by channel characteristics or peat properties. In contrast, changes in regional conditions such as climate and land cover across the upstream river basin have been shown to influence the river hydrograph but have a limited effect on peat growth. These results demonstrate that alluvial-peatland development is strongly determined by the geomorphic boundary conditions set by the river network and as such models must account for river channel dynamics to adequately simulate peatland development trajectories in valley environments.
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Gurung, Narayan, Monique Fort, Rainer Bell, Gilles Arnaud-Fassetta, and Narayan Raj Maharjan. "Hydro-torrential hazard vs. anthropogenic activities along the Seti valley, Kaski, Nepal: Assessment and recommendations from a risk perspective." Journal of Nepal Geological Society 62 (September 14, 2021): 58–87. http://dx.doi.org/10.3126/jngs.v62i0.38695.
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The Seti River originates from the Annapurna Massif in the Higher Himalaya of Nepal and flows through the Pokhara valley in the Lesser Himalaya. The Seti River witnessed a disastrous flash flood on May 5th, 2012 causing the death of 72 people, obliterating dozens of homes and damaging infrastructures worth millions of dollars. Despite the 2012 flood event and several warnings by scientists for more yet bigger scale future floods in the Seti valley, fluvial risk is being aggravated by anthropogenic activities such as unplanned human settlement, encroachment of riverbanks, haphazard construction of road, drinking water, and hydropower projects in potential flood hazard areas in addition to the increased impacts of climate change on geological and hydro-metrological hazards as in other parts of Hindu Kush Himalayan Range. Covering some 40-km distance from the Seti headwater (Sabche Cirque) down to Pokhara city, the study is carried out based on hydro-geomorphological mapping, analysis of land-use and land-cover change, hydrological analysis including HEC-RAS modelling, historical archives, and interviews with local people. The study shows a significant change on the land use and land cover of the Seti catchment, mainly the urban/built-up area, which is increased by 405% in 24 years period (1996 to 2020) and by 47% in 7 years period (2013 to 2020). Further the study reveals that anthropogenic activities along the Seti valley have increased fluvial risk and are likely to invite more disasters. From the HEC-RAS analysis, two motor bridges built over Seti River were found to have insufficient freeboard to safely pass the highest flood discharge for 100 years return-period. Instead of relocating people to safer places, the government and local authorities rather seem to have encouraged people to live in the floodplain by providing basic amenities such as drinking water, electricity and access road. Given the context of climate change and Pokhara valley and the Seti catchment being in a high-seismic gap zone, there is a strong possibility of similar flood to the scale of 2012 or even greater in Seti River. Though the fluvial risk can be managed in a sustainable way through the application of functional space concept, i.e., by allowing more space (freedom) for rivers, this economic and environment friendly approach of the fluvial risk management has not been implemented yet in the Seti valley nor in Nepal. Rather the encroachment of floodplains by anthropogenic activities along the Seti valley is on an increasing trend. Many settlements and infrastructures along the valley have been identified vulnerable to hydro-torrential hazards, therefore it is utmost necessity to implement functional space river concept, land use and land plan policy, early warning system and public awareness education in order to mitigate and manage the future impact of fluvial hazards along the Seti valley.
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Kasprak, Alan, Joel B. Sankey, Daniel Buscombe, Joshua Caster, Amy E. East, and Paul E. Grams. "Quantifying and forecasting changes in the areal extent of river valley sediment in response to altered hydrology and land cover." Progress in Physical Geography: Earth and Environment 42, no. 6 (September 13, 2018): 739–64. http://dx.doi.org/10.1177/0309133318795846.
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In river valleys, sediment moves between active river channels, near-channel deposits including bars and floodplains, and upland environments such as terraces and aeolian dunefields. Sediment availability is a prerequisite for the sustained transfer of material between these areas, and for the eco-geomorphic functioning of river networks in general. However, the difficulty of monitoring sediment availability and movement at the reach or corridor scale has hindered our ability to quantify and forecast the response of sediment transfer to hydrologic or land cover alterations. Here we leverage spatiotemporally extensive datasets quantifying sediment areal coverage along a 28 km reach of the Colorado River in Grand Canyon, southwestern USA. In concert with information on hydrologic alteration and vegetation encroachment resulting from the operation of Glen Canyon Dam (constructed in 1963) upstream of our study reach, we model the relative and combined influence of changes in (a) flow and (b) riparian vegetation extent on the areal extent of sediment available for transport in the river valley over the period from 1921 to 2016. In addition, we use projections of future streamflow and vegetation encroachment to forecast sediment availability over the 20 year period from 2016 to 2036. We find that hydrologic alteration has reduced the areal extent of bare sediment by 9% from the pre- to post-dam periods, whereas vegetation encroachment further reduced bare sediment extent by 45%. Over the next 20 years, the extent of bare sediment is forecast to be reduced by an additional 12%. Our results demonstrate the impact of river regulation, specifically the loss of annual low flows and associated vegetation encroachment, on reducing the sediment available for transfer within river valleys. This work provides an extendable framework for using high-resolution data on streamflow and land cover to assess and forecast the impact of watershed perturbation (e.g. river regulation, land cover shifts, climate change) on sediment connectivity at the corridor scale.
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Gao, Cunhai. "Buried bedrock valleys and glacial and subglacial meltwater erosion in southern Ontario, Canada." Canadian Journal of Earth Sciences 48, no. 5 (May 2011): 801–18. http://dx.doi.org/10.1139/e10-104.
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Morphometric features from a recently compiled bedrock topography map by the Ontario Geological Survey suggest a glacial erosion origin for the buried large bedrock valleys and troughs in southern Ontario. The bedrock valleys at Milverton, Wingham and Mount Forest are tunnel valleys, resulting from subglacial meltwater erosion beneath the Huron ice lobe, probably during or shortly after the Late-Wisconsinan glacial maximum. Diagnostic features for this interpretation include abrupt valley beginning and termination, uneven longitudinal valley profiles and up-slope gradients. The Dundas bedrock valley is the western extension of the Lake Ontario Basin. No comparable bedrock valleys were found to connect it to the Milverton valley for a joint drainage system as previously suggested. The Laurentian bedrock trough is the southeastward extension of the Georgian Bay Basin, both developed along shale bedrock between the Precambrian shield highlands and the Niagara Escarpment, resulting from long-term mechanical weathering associated with Pleistocene glacial erosion. This bedrock low has a floor that exceeds 50 km in width and is 26 m and more below the current water level of Georgian Bay. It could drain Georgian Bay should the drift cover be removed. There is no evidence to suggest that a preglacial river channel, if it existed, is still preserved in the floor of the Laurentian trough as previously suggested. The framework for an intensely glacially sculpted bedrock surface differs from the previous view for simple modification of a preglacial landscape and is, therefore, important in regional subsurface geological mapping and groundwater studies.
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Demissie, Biadgilgn. "Ephemeral stream dynamics, land cover changes and climate variability in the marginal grabens of the northern Ethiopian Rift Valley." Afrika Focus 29, no. 2 (February 26, 2016): 93–100. http://dx.doi.org/10.1163/2031356x-02902007.
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This study focused on ephemeral streams morphodynamics and their relation with hydro-climatic and bio-physical characteristics in their headwater and graben floors in the marginal grabens along the northern Ethiopian Rift Valley. The Raya graben was taken as a case study area, which is the largest marginal graben in northern Ethiopia. The link between rainfall variability and land cover changes shows that there was a negative correlation between precipitation and deforestation which implies that an increase in precipitation decreases deforestation deterring the peasants from tree cutting. Regarding the relationship between upper catchment characteristics and river morphology, results show that upper catchment area is the most important controlling factor of the length of and the area occupied by the rivers in the graben bottom. A simple hydraulic analysis based on the change of specific discharge as the river flow approaches the bridges demonstrates that the abrupt change in channel width as the river approaches the bridge is the main cause of the thick deposition and, consequently, of the increased frequency of overbank floods upstream of the road bridges in the study area. The results related to channel bank erosion capacity of flash floods show that all the peak discharges were equally important in triggering channel bank erosion. Concomitantly, vegetated channels are much more resistant to channel bank erosion than non-vegetated banks. Land changes in graben bottoms dictate that the changes are not simply related to a distributary river system but that human intervention (e.g., the conversion of bushland and forests into cropland, settlement on alluvium, and avoidance of losing farmland to other land units) and natural vegetation regeneration (e.g., alluvial deposits into shrubland) are also important. Overall, the study suggests that to control the morphodynamics of the ephemeral rivers and their impact on farming activities in the graben bottom, catchment rehabilitation activities need to focus both on the upper catchment and the river channels in the graben bottom.
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Mandarino, Andrea, Giacomo Pepe, Andrea Cevasco, and Pierluigi Brandolini. "Quantitative Assessment of Riverbed Planform Adjustments, Channelization, and Associated Land Use/Land Cover Changes: The Ingauna Alluvial-Coastal Plain Case (Liguria, Italy)." Remote Sensing 13, no. 18 (September 20, 2021): 3775. http://dx.doi.org/10.3390/rs13183775.
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The active-channel planform adjustments that have occurred along the Centa, lower Arroscia and lower Neva rivers since 1930, along with the riverbed channelization processes and the land-use and land-cover changes in disconnected riverine areas, were investigated through a multitemporal analysis based on remote sensing and geographical information systems (GIS). These watercourses flow through the largest Ligurian alluvial-coastal plain in a completely anthropogenic landscape. This research is based on the integrated use of consolidated and innovative metrics for riverbed planform analysis. Specific indices were introduced to assess active-channel lateral migration in relation to the active-channel area abandonment and formation processes. The Arroscia and Neva riverbeds experienced narrowing, progressive stabilization, and braiding phenomena disappearance from 1930 to the early 1970s, and then slight narrowing up to the late 1980s. Subsequently, generalized stability was observed. Conversely, the Centa was not affected by relevant planform changes. Recently, all rivers underwent a slight to very slight width increase triggered by the November 2016 high-magnitude flood. The active-channel adjustments outlined in this paper reflect the relevant role in conditioning the river morphology and dynamics played by channelization works built from the 1920s to the early 1970s. They (i) narrowed, straightened, and stabilized the riverbed and (ii) reduced the floodable surface over the valley-floor. Thus, large disconnected riverine areas were occupied by human activities and infrastructures, resulting in a progressive increase in vulnerable elements exposed to hydrogeomorphic hazards. The outlined morphological dynamics (i) display significant differences in terms of chronology, type, and magnitude of active-channel planform adjustments with respect to the medium- and short-term morphological evolution of most Italian rivers and (ii) reflect the widespread urbanization of Ligurian major valley floors that occurred over the 20th century. The outcomes from this study represent an essential knowledge base from a river management perspective; the novel metrics enlarge the spectrum of available GIS tools for active-channel planform analysis.
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Szpikowski, Józef, Mikołaj Majewski, and Wojciech Madaj. "Conditions for soil erosion by water in the upper Parsęta catchment." Landform Analysis 36 (December 30, 2018): 55–69. http://dx.doi.org/10.12657/landfana.036.006.
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The paper presents potential soil erosion risk of the upper Parsęta catchment (Drawskie Lake District, NW Poland). The model considers following conditions affecting the size of soil erosion: slope gradient, LS factor, lithology, land use and land cover. Thematic maps have been reclassified into a 4-degree division. Potential soil erosion risk map was prepared on the basis of thematic maps. Areas with small and moderate susceptibility to soil erosion occupy 71.5% of the catchment area. The 4th class of erosiveness is represented by the river valley slopes, steep slopes of kame and moraine hills, covering 28.5% of the upper Parsęta catchment.
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Tsyrenova, Marina, Evgenia Pyzhikova, and Elena Vasilyeva. "Anthropogenic Vegetation in the River Valley Amalat." BIO Web of Conferences 16 (2019): 00049. http://dx.doi.org/10.1051/bioconf/20191600049.
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The article presents the results of a research study of anthropogenic affects of gold mining on forest landscapes in Northern Transbaikalia, Russia and processes of natural reclamation of vegetation cover of the disturbed areas. The study area is located northwest of the Maliy Amalat River, which flows along the Vitim Plateau; in the floodplains of its two tributaries the Aunik River and the Bagdarin River. It is an area where a large number of alluvial gold deposits have been discovered. Some of these deposits are currently being developed, some have already been explored, and some have been abandoned. The authors consider the current state of vegetation cover in a key area of the Amalat River basin, near villages of Malovsky and Bagdarin. The problem of natural resources development and conservation is becoming extremely important for the area under study because open-pit gold mining methods that are used here drastically change the environment and affect water, land and forest resources.
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Jiang, Qinhua, and Dolores R. Piperno. "Environmental and Archaeological Implications of a Late Quaternary Palynological Sequence, Poyang Lake, Southern China." Quaternary Research 52, no. 2 (September 1999): 250–58. http://dx.doi.org/10.1006/qres.1999.2070.
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Paleoecological data from Poyang Lake, southern China, indicate that significant natural and human-induced vegetational changes have occurred during the Late Quaternary in the Middle Yangtze River valley, the likely location of rice (Oryza sativa L.) domestication. During the late Pleistocene (from ca. 12,830 to ca. 10,500 yr B.P.), the climate was cooler and drier than today's. The subtropical, mixed deciduous–evergreen broad-leaved forest which constitutes the modern, potential vegetation was reduced and herbaceous vegetative cover expanded. A hiatus in sedimentation occurred in Poyang Lake, beginning sometime after ca. 10,500 yr B.P. and lasting until the middle Holocene (ca. 4000 yr B.P.). At ca. 4000 yr B.P., the regional vegetation was a diverse, broad-leaved forest dominated by many of the same arboreal elements (e.g., Quercus, Castanopsis, Liquidambar) that grow in the area today. A significant reduction of arboreal pollen and an increase of herbaceous pollen at ca. 2000 yr B.P. probably reflect human influence on the vegetation and the expansion of intensive rice agriculture into the dryland forests near the river valleys.
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Gilbert, Robert, and Joseph R. Desloges. "The record of Glacial Lake Champagne in Kusawa Lake, southwestern Yukon Territory." Canadian Journal of Earth Sciences 42, no. 12 (December 1, 2005): 2127–40. http://dx.doi.org/10.1139/e05-094.
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Late Pleistocene glaciers dammed Glacial Lake Champagne in the valley of Dezadeash River between a westward-flowing glacier in the Takhini valley and eastward-flowing glaciers from the St. Elias complex. Modern Kusawa Lake lies in the southern extension of Lake Champagne. Geophysical and geomorphic evidence documents the deglaciation of the lake, the presence of Lake Champagne, and the postglacial sedimentary environment of the basin. During the main phase of Lake Champagne, the water level stood at 772 m in the northern part of Kusawa Lake and 756 m in northern Dezadeash valley, both probably controlled by a spillway floored at 756 m to the north into the Nordenskiold River. This indicates differential isostatic rebound of 0.2 m/km from south to north. At that time a trunk glacier occupied the southern portion of Kusawa Lake, depositing a thick sequence of sediment in the basin. A glacier in the Primrose valley and the Takhini trunk glacier built large deltas into Lake Champagne. Subsequently, the level fell to 744 m, controlled by a spillway around the sediment plug at the outlet of Kusawa Lake, and the trunk glacier retreated from Kusawa Lake. Lacustrine sediment washed from the now substantially exposed valley sides was deposited as a distinctive facies in the north-central portion of Kusawa Lake. Incision of the delta at the outlet of the lake lowered its level to a major strandline at 714 m and eventually to its present level of 671 m. In the southern portion of the lake, a single sedimentary facies documents continuous glacilacustrine deposition from sediment originating in tributary basins still containing 11%14% glacier cover.
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Lučan, Radek K., Antonín Reiter, Josef Chytil, Ivan Horáček, and Tomáš Bartonička. "Pipistrellus kuhlii in the Czech Republic: 2007–2020 (Chiroptera: Vespertilionidae)." Lynx new series 51, no. 1 (2021): 81–94. http://dx.doi.org/10.37520/lynx.2020.007.
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Based on 25 records (both published and new) we summarize the recent distribution of Pipistrellus kuhlii in the Czech Republic and discuss possible colonization routes. The species colonized a major part of the Czech Republic during 14 years since its first record in 2007. Based on locations and chronology of the records it seems that the eastern part of the Czech Republic (Moravia) was colonized from the south along the Dyje and Morava rivers, while in Bohemia, two possible routes may have existed: one from the south along the Vltava river from the Danube valley, and another from the east or south-east along the valley of the Svitava and Orlice rivers. Given the fact that already in 2018 the presence of P. kuhlii was confirmed in Saxony, which predated the species confirmation in the north-western and central parts of Bohemia, we do not exclude possible existence of a third colonization route along the Labe river from the north-west (Germany). All the records come from human settlements, typically cities or towns, and dates of the records suggests the year-round occurrence. At least four records (including two roosts of maternity colonies), all from Moravia, proved reproduction of this bat in the country. All examined individuals displayed pelage and skin colouration patterns typical for P. kuhlii kuhlii.
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Acharjee, Shukla, Rajib Tarani Das, Shubhendu Shekhar, Neelratan Singh, Uttam Goswami, M. M. G. S. Dilini, Y. K. Mawale, B. K. Iyengar, and R. S. Negi. "Channel Migration and Consequential Land Use Land Cover Changes of Subansiri River, Assam, North-Eastern India." IOP Conference Series: Earth and Environmental Science 1032, no. 1 (June 1, 2022): 012009. http://dx.doi.org/10.1088/1755-1315/1032/1/012009.
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Abstract Subansiri River is the largest tributary of the Brahmaputra River running through the Indian states of Assam and Arunachal Pradesh, and Tibet, the Autonomous Region of China. The Subansiri River is 442 km long with a drainage basin of 32,640 km2 and it contributes approximately 7.92% of the Brahmaputra’s total flow. Sequential Channel shifting has been witnessed as the most important characteristic of the Subansiri River of Assam. The detailed study on channel migration of the present course of the Subansiri River through the upper floodplain of Brahmaputra valley indicates that the area is under active erosion for a long time. Therefore, an attempt has been made to understand the relationship between the rate of channel migration and successive land use/land cover changes in its surrounding floodplain area. The Support Vector Machine (SVM) and the Artificial Neural Network (ANN) algorithms are applied on Landsat images of the years 1973, 1988, 2001, and 2017 for generating land use/land cover maps through supervised classification technique. The overall accuracy of the land use/land cover classification ranges between 81% (for the year 1988) and 84% (for the year 2017). The land use/land cover maps show an increase in the built-up area and a decrease in the agricultural area. The change has been observed vis-a-vis channel migration indicating that the migration directly affects the floodplain habitats which in turn affects the land use, Findings of this study highlight geomorphological instabilities of the study area and the vulnerability of the habitations residing near the Subansiri river.
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Nikolic, Jovanka, Shiyuan Zhong, Lisi Pei, Xindi Bian, Warren E. Heilman, and Joseph J. Charney. "Sensitivity of Low-Level Jets to Land-Use and Land-Cover Change over the Continental U.S." Atmosphere 10, no. 4 (April 2, 2019): 174. http://dx.doi.org/10.3390/atmos10040174.
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Lower-tropospheric wind maxima, known as low-level jets (LLJs), play a vital role in weather and climate around the world. In this study, two 10-year (2006–2015) regional climate simulations using current (2011) and future (2100) land-use/land-cover (LULC) patterns over the continental United States (CONUS) are used to assess the sensitivity of LLJ properties, including jet occurrence, maximum speed, and the elevation of the maximum, to changes in LULC. The three simulated LLJ properties exhibit greater sensitivity in summer than in winter. Summertime jets are projected to increase in frequency in the central CONUS, where cropland replaces grassland, and decrease in parts of the Ohio-River Valley and the Southeast, particularly Florida, where urban expansion occurs. Little change is projected for wintertime jet frequency. Larger modifications to jet speed and elevations are projected in parts of the Ohio River Valley, the upper Southeast, and the Intermountain West. While there is some evidence of weaker, more elevated jets with urban expansion, the connection between changes in jet speed and elevation and changes in LULC patterns at a given location is weak. This result suggests that LULC will primarily affect the large-scale atmospheric conditions that contribute to the formation of LLJs, particularly in winter.
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Cobb, Charles R., and Paul A. Webb. "A Source Area Perspective on Expedient and Formal Core Technologies." North American Archaeologist 15, no. 3 (January 1995): 197–219. http://dx.doi.org/10.2190/yyfn-qlm5-fhpu-4vey.
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The Hollister Lake site represents a combined quarry and habitation area located in the Hudson River valley, New York. Excavations at the site revealed the exploitation of Onondaga chert through several time periods, predominately the Late Archaic. Lithic production at the Hollister Lake site seems to have been oriented toward both an expedient amorphous core technology and a formal biface core technology. The interdependence of these technologies is explored with respect to regional patterns of group mobility, and raw material distribution and quality.
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V, Ganesh, Ajey Kumar V G, Aravindan S, Sudha Ravindranath, and Vidya A. "Estimation and Analysis of Rainfall Runoff for Urban Hydrology using TR 55 SCS CN and GIS Approach in Hebbal Valley of Bengaluru, South India." International Journal of Recent Technology and Engineering (IJRTE) 10, no. 3 (September 30, 2021): 215–20. http://dx.doi.org/10.35940/ijrte.c6484.0910321.
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Urban floods are increasing frequently and severely. Climate change is usually attributed to urban floods with insufficient evidence. While in certain cases this appears to be true, the influence of landscape change in urban growth is more important. This study analyses development of an urban landscape with the complexity of established cities and combines physiographic data for the assessment of peak surface runoff in the study area, Hebbal valley. A portion of the Cauvery river basin draining into the Pinakini river in the district of Bangalore. It encompasses a 305.21 sq.km region in East Bengaluru and North Bengaluru. The land use and land cover classification was classified as 14 different categories: dark, light, roads and vegetation. The region of study has undergone unpredictable expansion and changes in the Land Use Land Cover in the last two decades. Several flood occurrences have occurred in different regions of Hebbal Valley throughout recent years. Rainfall analysis conducted between 1970 and 2018 with 1596mm of greatest precipitation. For the study, several space and non-space data were collected and thematic maps were produced. Runoff estimates for 2018 were made for 24 micro water sheds in the Hebbal Valley using SCS-CN TR55 technique for urban hydrology. The objective of this study is to determine the quantity of peak runoff produced, to develop better urban management techniques. The finding shows that rush volume has increased in recent years as land use patterns have changed and precipitation intensity has increased substantially over shorter periods. The study suggests spatial intervention efforts to provide suitable buildings and measures for flood flow.
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Rikiishi, Kunio, and Junko Sakakibara. "Seasonal cycle of the snow coverage in the former Soviet Union and its relation with atmospheric circulation." Annals of Glaciology 38 (2004): 106–14. http://dx.doi.org/10.3189/172756404781815059.
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AbstractHistorical snow-depth observations in the former Soviet Union (FSU) during the period September 1960–August 1984 have been analyzed in order to understand the seasonal cycle of snow coverage in the FSU. Snow cover first appears in September in northeastern regions, and spreads over the entire territory before early January. Snowmelt begins in mid-January in the southern regions and then snow cover retreats rapidly northward until it disappears completely before late June. Northward of 60°N, the land surface is snow-covered for more than half the year. The longest snow-cover duration is observed on the central Siberian plateau (about 9.5 months) and along the Arctic coastal regions (about 8.5 months). One of the most conspicuous features of the snow coverage in the FSU is that the length of the snow-accumulation period differs considerably from region to region (2–7 months), while the length of the snowmelt period is rather short and uniform over almost the entire territory (1–2 months). Although the maximum snow depths are 20–50 cm in most regions of the FSU, they exceed 80 cm in the mountainous regions in central Siberia, Kamchatka peninsula, and along theYenisei river valley. Values for the maximum snow depth are very small along the Lena river valley in spite of the air temperature being extremely low in winter. By calculating correlation coefficients between the snowfall intensities and the sea-level pressures or 500 hPa heights, it is shown that deep snow along the Yenisei river valley is caused by frequent migration of synoptic disturbances from the Arctic Ocean. Snowfalls along the Lena river valley are also caused by traveling disturbances from the Arctic Ocean. Snow accumulation is suppressed after the Arctic Ocean has been frozen.
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White, James M., Rolf W. Mathewes, and W. H. Mathews. "Late Pleistocene Chronology and Environment of the “Ice-Free Corridor” of Northwestern Alberta." Quaternary Research 24, no. 2 (July 1985): 173–86. http://dx.doi.org/10.1016/0033-5894(85)90004-3.
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Pollen and macrofossil analyses of two radiocarbon-dated lake sediment cores in the upper Peace River district were used to investigate the controversial late-glacial geochronology of the “ice-free corridor.” The basal mineral-rich sediments contain reworked, radiogenically “dead” palynomorphs, as well as intrusive “modern” carbon. Analyses of the basal sediments from Boone Lake show that two 14C ages greater than 12,000 yr B.P. are spuriously old due to contamination by organic matter of Cretaceous age. The data support occlusion or near occlusion of Laurentide and Cordilleran ice in the Peace River area during the late Wisconsinan period. The sediment record began around 12.000 yr B.P. in the ice-dammed and enlarged Boone Lake. An initially open, sedge-dominated cover was invaded by sage, willow, grass, and poplar by 11,700 yr B.P., suggesting that a habitable landscape has existed in the area for at least 12 millennia. The data, however, do not support the ice-free corridor arguments of B. O. K. Reeves (1973, Arctic and Alpine Research 5, 1–16; 1983, In “Quaternary Coastlines and Marine Archaeology: Towards the Prehistory of Land Bridges and Continental Shelves” (P. M. Masters and N. C. Fleming, Eds.), pp. 389–411. Academic Press, New York), who suggests that ice occlusion did not occur in the Peace River Valley during the last 55,000 yr.
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Ku, Teh-Lung, Shangde Luo, Tim K. Lowenstein, Jianren Li, and Ronald J. Spencer. "U-Series Chronology of Lacustrine Deposits in Death Valley, California." Quaternary Research 50, no. 3 (November 1998): 261–75. http://dx.doi.org/10.1006/qres.1998.1995.
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Uranium-series dating on a 186-m core (DV93-1) drilled from Badwater Basin in Death Valley, California, and on calcareous tufas from nearby strandlines shows that Lake Manly, the lake that periodically flooded Death Valley during the late Pleistocene, experienced large fluctuations in depth and chemistry over the last 200,000 yr. Death Valley has been occupied by a long-standing deep lake, perennial shallow saline lakes, and a desiccated salt pan similar to the modern valley floor. The average sedimentation rate of about 1 mm/yr for core DV93-1 was punctuated by episodes of more-rapid accumulation of halite. Arid conditions similar to the modern conditions prevailed during the entire Holocene and between 120,000 and 60,000 yr B.P. From 35,000 yr B.P. to the beginning of the Holocene, a perennial saline lake existed, over 70 m at its deepest. A much deeper and longer lasting perennial Lake Manly existed from about 185,000 to 128,000 yr B.P., with water depths reaching about 175 m, if not 330 m. This lake had two significant “dry” excursions of 102–103yr duration about 166,000 and 146,000 yr B.P., and it began to shrink to the point of halite precipitation between 128,000 and 120,000 yr B.P. The two perennial lake periods correspond to marine oxygen isotopic stages (OIS) 2 and 6. Based on the shoreline tufa ages, we do not rule out the possible existence ∼200,000 yr ago of yet a third perennial lake comparable in size to the OIS 6 lake. The234U/238U data suggest that U in tufa owes its origin mainly to Ca-rich springs fed by groundwater that emanated along lake shorelines in southern Death Valley, and that an increase of this spring-water input relative to the river-water input apparently occurred during OIS 6.
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Shi, Mingjie, Hongqi Wu, Xin Fan, Hongtao Jia, Tong Dong, Panxing He, Muhammad Fahad Baqa, and Pingan Jiang. "Trade-Offs and Synergies of Multiple Ecosystem Services for Different Land Use Scenarios in the Yili River Valley, China." Sustainability 13, no. 3 (February 2, 2021): 1577. http://dx.doi.org/10.3390/su13031577.
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Environmental managers and policymakers increasingly discuss trade-offs between ecosystem services (ESs). However, few studies have used nonlinear models to provide scenario-specific land-use planning. This study determined the effects of different future land use/land cover (LULC) scenarios on ESs in the Yili River Valley, China, and analyzed the trade-offs and synergistic response characteristics. We simulated land-use changes in the Yili River Valley during 2020–2030 under three different scenarios using a patch-generating land-use simulation (PLUS) model—business as usual (BAU), economic development (ED), and ecological conservation (EC). Subsequently, we evaluated the water yield (WY), carbon storage (CS), soil retention (SR), and nutrient export (NE) ESs by combining the PLUS and integrated valuation of ecosystem services and trade-offs (InVEST) models, thus exploring multiple trade-offs among these four ESs at a regional scale. For the BAU scenario, there are some synergistic effects between WY and SR in the Yili River Valley, in addition to significant trade-off effects between CS and NE. For the ED scenario, the rapid expansion of cropland and constructed land is at the expense of forested grassland, leading to a significant decline in ESs. For the EC scenario, the model predicted that the cumulative regional net future carbon storage, cumulative water retention, and cumulative soil conservation would all increase due to ecological engineering and the revegetation of riparian zones and that formerly steep agricultural land can be effective in improving ESs. Meanwhile, the trade-off effect would be significantly weakened between CS and NE. These results can inform decision makers on specific sites where ecological engineering is implemented. Our findings can enhance stakeholders’ understanding of the interactions between ESs indicators in different scenarios.
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Negi, Vivek, and Mohammad Irfan. "Land Use/Cover Mapping and Change Detection Using Remote Sensing Techniques: A Case of Upper Kullu Valley, Himachal Pradesh." Current World Environment 17, no. 2 (September 10, 2022): 417–26. http://dx.doi.org/10.12944/cwe.17.2.13.
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The land use/cover change has remained an important indicator in explaining the regional and global environmental issues and their determinants. The present study is an attempt to analyze the land use/cover change as a way of measuring visual impressions of landscape transformation in the Upper Kullu Valley of Himachal Pradesh. In the recent decades, the area has experienced considerable land use/cover changes due to urbanization, commercial agriculture and tourism activities. These developmental activities have hugely impacted the natural resources, bio-capacity and land availability of the area. The land use/cover has been analyzed with the help of LANDSAT imageries from 1991 to 2020. Supervised classification has been done on selected images by using maximum likelihood classifier (MLC). The study has been done on eight LULC classes namely, agricultural/horticultural land, built-up land, forest cover, pasture/open land, barren land, snow cover, river/water-bodies and sandy surface. The result shows decrease in snow cover and forest cover and increase in barren land, agricultural/horticultural land and built-up area during 1991-2020. The limited land resources and growing urbanisation are making these changes more complex. Therefore, continuous monitoring of these processes and subsequent changes are necessary for future planning and resource management.
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Kuzyk, Ihor, Ihor Vitenko, and Volodymyr Tsaryk. "GEOECOLOGICAL ASSESSMENT OF LAND USE STRUCTURE OF GNIZDECHNA SMALL RIVER BASIN." SCIENTIFIC ISSUES OF TERNOPIL VOLODYMYR HNATIUK NATIONAL PEDAGOGICAL UNIVERSITY. SERIES: GEOGRAPHY 52, no. 1 (May 30, 2022): 219–21. http://dx.doi.org/10.25128/2519-4577.22.1.26.
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Gnizdechna river is a right tributary of the Gnizna river (Dniester basin) and flows in the central part of the Ternopil region. The length of the river is 39 km, the area of the basin is 26 400 ha, the average depth is 1,5 m, the slope of the river is 1,8 m/km. The valley of the Gnizdechna river is partially melioration and regulated, there are 4 ponds on the river. The aim of the article is to assess the geo-ecological parameters of the land use structure of the small Gnizdechna river basin. The following methods were used to achieve this goal: descriptive, geoinformation, statistical, mathematical and geoecological analysis, as well as special methods for determination the anthropogenic load, coefficients of ecological stability and anthropogenic transformation of the Gnizdechna river basin. The structure of land lands in the Gnizdechna river basin was analyzed. It was found that the structure of land use of the study area is dominated by arable land (65%), forests occupy 10%, built-up land - 6%, pastures - 9%, hayfields - 5%, perennials – 1,5%, land under water and swamps – 1,5%. The share of natural lands in the Gnizdechna river basin is 27%. The reserve of the basin is 17% (22 objects of the nature reserve fund, with a total area of 4420,5 hectares).
According to the results of calculations, the article defines the coefficient of anthropogenic transformation landscapes of the Gnizdechna river basin which is 5,88; the coefficient of ecological stability of the study area - 0,3; anthropogenic load score - 3,7; anthropogenic load factor - 3,3. According to the obtained results, it is established that the territory of the Gnizdechna river basin is ecologically unstable with moderately transformed landscapes, rather high score and average degree of anthropogenic load. The prospect of further research remains the rationale for measures to optimize the structure of land use in the Gnizdechna river basin, in which it is necessary to provide for an increase in the forest cover of the study area by changing the purpose of individual land plots and the organization of their landscape-adapted use.
According to the results of the geoecological assessment of the land use structure of the Gnizdechna river basin, it can be concluded that the landscapes of the study area are moderately transformed, ecologically unstable with a sufficiently high anthropogenic load. Such indicators are due to high agricultural development of the basin (82%) and, accordingly, plowing - 65%, low share of forested land (10%) and other natural lands (pastures, hayfields, perennials, underwater lands and swamps - 17%) . Which in turn forms a low share of natural lands in the basin of the studied small river - 27%. At the same time, in the basin of the river Gnizdechna there are 22 objects of the nature reserve fund with a total area of 4420.4 hectares, which forms a reserve of the studied area of 17%. To optimize the structure of land use in the Gnizdechna River basin, it is necessary to justify and implement a number of measures, which should be based on landscape-adapted land use, reduce plowing and increase forest cover, due to unproductive and highly eroded lands. The formation of an ecologically safe system of nature management in the basin of the studied small river will help to improve the geo-ecological situation in the basins of the rivers Gnizna, Seret and Dniester.
Key words: Gnizdechna river, river basin, land use, anthropogenic load, natural lands, Ternopil region.
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Chen, Wenqian, Jianli Ding, Jingzhe Wang, Junyong Zhang, and Zhe Zhang. "Temporal and spatial variability in snow cover over the Xinjiang Uygur Autonomous Region, China, from 2001 to 2015." PeerJ 8 (April 8, 2020): e8861. http://dx.doi.org/10.7717/peerj.8861.
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Xinjiang, China, is a typical arid and semi-arid region of Central Asia that significantly lacks freshwater resources, and the surface runoff in this region is mainly supplied by mountain glacier and snow cover meltwater. Based on the above background and issues of transnational water resources between Xinjiang and Central Asia along the Silk Road Economic Belt, which were highlighted in the major strategy of “The Belt and Road”, this study analysed the spatial and temporal variations in snow cover and snow cover days in the Xinjiang region from 2001 to 2015. The study area includes four subregions: Northern Xinjiang, Southern Xinjiang, Eastern Xinjiang and the Ili River Valley. Moderate-resolution Imaging Spectroradiometer (MODIS) 8-day snow cover data were used after removing clouds by combining MOD10A2 and MYD10A2. The results showed that seasonal snow cover occurred from October to April in most regions of Xinjiang and that this snow cover consisted of two processes: snow accumulation and snow ablation. The maximum snow cover occurred in January, whereas the minimum snow cover occurred from July to August. During the seasonal snow cover period, the snowfall rates in Northern Xinjiang and the Ili River Valley were higher, while the other regions had a low snowfall probability. To study the relationship between altitude and snow cover, the normalized snow elevation correlation index (NSACI) was calculated. The NSACI showed a significant correlation between snow cover and elevation in most regions of Xinjiang and was classified into five grades. Snow cover days did not fluctuate obviously from 2001 to 2015, and a decreasing trend was observed in the four subregions except for the Ili River Valley (nonsignificant decreasing trend). We also observed a correlation between snow cover and temperature and found that the correlations between monthly snow cover and monthly temperature in the four subregions were strongly related to the underlying land type and global warming background, which also suggests that the special topography of Xinjiang greatly influences both snow cover and climate change.
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Matysik, Magdalena, Damian Absalon, Michał Habel, and Michael Maerker. "Surface Water Quality Analysis Using CORINE Data: An Application to Assess Reservoirs in Poland." Remote Sensing 12, no. 6 (March 18, 2020): 979. http://dx.doi.org/10.3390/rs12060979.
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Reservoirs are formed through the artificial damming of a river valley. Reservoirs, among others, capture polluted load transported by the tributaries in the form of suspended and dissolved sediments and substances. Therefore, reservoirs are treated in the European Union (EU) as “artificial” or “heavily modified” surface water bodies. The reservoirs’ pollutant load depends to a large extent on the degree of anthropogenic impact in the respective river catchment area. The purpose of this paper is to assess the mutual relation between the catchment area and the reservoirs. In particular, we focus on the effects of certain land use/land cover on reservoirs’ water quality. For this study, we selected twenty Polish reservoirs for an in-depth analysis using 2018 CORINE Land Cover data. This analysis allowed the identification of the main triggering factors in terms of water quality of the respective reservoirs. Moreover, our assessment clearly shows that water quality of the analysed dam reservoirs is directly affected by the composition of land use/land cover, both of the entire total reservoir catchment areas and the directly into the reservoir draining sub-catchment areas.
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Kotsev, Tsvetan, and Velimira Stoyanova. "Application of geographic data for spatial modeling of lead in contaminated fluvial soils." Journal of the Bulgarian Geographical Society 47 (November 25, 2022): 23–33. http://dx.doi.org/10.3897/jbgs.e97168.
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The present study aims to determine the spatial distribution of soils with lead (Pb) content above the quality thresholds in a section of the Ogosta River valley (NW Bulgaria). The study area was contaminated with mine waste from the extraction and flotation of iron, lead-silver, and gold-bearing ores in the second half of the XX century. Predictive modeling was performed with the software Maximum Entropy Species Distribution Modeling (MaxEnt), Version 3.4.4, which uses machine learning algorithms and applies the maximum entropy method. The choice of predictors of contaminated soil distribution is consistent with the main factor for Pb dispersal within the valley floor - flooding from the Ogosta River. The following six parameters explained the environmental settings related to the accumulation of contaminated floodplain sediment: vertical distance to the river channel, lateral distance to the Ogosta River, terrain slope, land cover (CORINE Land Cover, 2019), morphographic units of topography, and elevation. The results represent the average values of 10 replicates of the model. We evaluated the individual models by the value of the area under the relative operating characteristic curve (AUC) and the geographic logic of the obtained results. The AUC score for the test samples was 0.666 for the soil group 1 with Pb ≤120 mg/kg, 0.782 for group 2 with Pb (120-500] mg/kg, and 0.934 for group 3 with Pb>500 mg/kg. The most significant predictors for the models are the vertical and lateral distance to the river and the slope of the terrain. Lead concentrations tend to decrease with the distance from the main river and by increasing the elevation above the river channel due to lower inundation frequency and deposition rate of polluted river sediments. The soils with a Pb concentration below the permissible threshold of 120 mg/kg cover more than 58.42% of the valley floor of the studied section, and lands with Pb content above the intervention value of 500 mg/kg occupy nearly 10.82% of the investigated territory. The selected predictors describe the distribution of highly contaminated soils well and define the range of soils with lower Pb content worse. Combining clean and contaminated soil samples into one group is considered the main reason for the poor performance of MaxEnt for soils with Pb ≤120 mg/kg. However, the results prove the model's ability to predict the spatial distribution of not only biological species but also the dispersal of hazardous substances in soil.
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Petrovska, Ivana, and Lazo Dimov. "AUTOMATIC CLASSIFICATION OF LAND COVER USING MULTISPECTRAL SATELLITE IMAGERY: VALLEY OF RIVER TRESKA, MACEDONIA." Scientific Journal of Civil Engineering 9, no. 1 (2020): 105–9. http://dx.doi.org/10.55302/sjce2091105p.
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Dyer, Jamie. "Analysis of a Warm-Season Surface-Influenced Mesoscale Convective Boundary in Northwest Mississippi." Journal of Hydrometeorology 12, no. 5 (October 1, 2011): 1007–23. http://dx.doi.org/10.1175/2011jhm1326.1.
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Abstract The lower Mississippi River alluvial valley in southeastern Arkansas, northeastern Louisiana, and northwestern Mississippi is characterized by widespread agriculture with few urban areas. Land use is predominantly cultivated cropland with minimal topographic variation; the eastern edge of the alluvial valley is defined by a rapid, although small, change in elevation into a heavily forested landscape, however. This change in land use/land cover has been shown to potentially enhance precipitation through generation of a weak mesoscale convective boundary. This project defines the influence of the land surface on associated precipitation processes by simulating a convective rainfall event that was influenced by regional surface features. Analysis was conducted using a high-resolution simulated dataset generated by the Weather Research and Forecasting Model (WRF). Results show that the strongest uplift coincides with an abrupt low-level thermal boundary, developed primarily by a rapid change from sensible to latent heat flux relative to the agricultural and forested areas, respectively. In addition, surface heating over the cultivated landscape appears to destabilize the boundary layer, with precipitation occurring as air is advected across the land cover boundary and the associated thermal gradient. This information can be used to define and predict surface-influenced convective precipitation along agricultural boundaries in other regions where the synoptic environment is weak.
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Li, Hui, Wen Jing Yao, Peng Fei Su, Qiu Chen Duan, and Guo Yan Li. "Shangri-La County Ecological Risk Evaluation Based on RS and GIS." Advanced Materials Research 663 (February 2013): 773–76. http://dx.doi.org/10.4028/www.scientific.net/amr.663.773.
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The world natural heritage Three Parallel Rivers core area Shangri-la County faced all kinds of ecological risk, and ecological risk assessment contributes to the ecological risk management. Have chosen the 10 main types landscape in the area as risk receptors, and ensured main risk source in the area to be forest fires, landslides and mudslides, urban construction, tourism, and the wood used for building and life, and have carried through the exposure and hazard analysis. Based on RS and GIS, first have calculated the landscape pattern index in the area, and then used landscape pattern index constructed landscape loss index as the ecological damage index. According proposed regional ecological risk assessment index system by this paper, and overlaid the influence distribution map of main risk source, and has obtained the comprehensive ecological risk value of every unit in combination with the calculation model. The ecological risk value were classified, eventually have obtained 1990 and 2006 spatial distribution of the ecological risk assessment in Shangri-la County. The results show that high-risk area distributes banding on Jinsha river downstream river valley area and Jaintang town area. Middle-risk areas distribute mainly on middle and lower reaches Jinsha river basin in Shangri-la County. Low-risk area distributes mainly inside middle-risk area that is main production area in Shangri-la County. Weak-risk area distributes mainly relatively high elevation area such as the snow and ice land and bare land, etc. The study can be applied to the similar type high canyon landscape risk assessment research.
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Smagin, V. A. "Mire vegetation in the basin of the Muroyagun River (Surgut Polesje, West Siberia)." Vegetation of Russia, no. 4 (2003): 62–77. http://dx.doi.org/10.31111/vegrus/2003.04.62.
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The author’s field research, performed in July 2000, was aimed at the descriptive survey of the diversity of mire vegetation in the poorly known West Siberian area, the so called Surgut Polesje. The palsa ridge-and-lake and palsa ridge-and-pool bog complexes dominate the area landscape. Such bogs make for the core of vast and heterogeneous mire systems, the other elements of the latter being transitional bogs and treeless or wooded fens. The mire systems are separated from each other only by rivers; the fens are located on river valley slopes. The following mire vegetation complexes (mire sites) were described: 1) oligotrophic palsa ridge-and-lake or palsa ridge-and-pool; 2) palsa ridge-and-hollow; 3) mesotrophic or heterotrophic aapa-mire; 4) mesotrophic-eutrophic sedge or sedge-peatmoss poor fen; 5) wooded sedge fen with low Betulatortuosa; 6) wooded sedge fen with one or two layers of Pinussibirica and Betulapubescens. The investigated mire vegetation displays a high degree of syntaxonomical diversity, belonging to the 4 classes, Oxycocco-Sphagnetea, Scheuchzerio-Cariceteanigrae, Phragmito-Magnocaricetea,and Alneteaglutinosae, with 4 orders, 6 alliances, and 8 associations, listed in the tables. There are no rare communities in the area, to the possible exception of some types of wooded sedge fens. The mire system margins along rivers and flowing lakes seem to be potentially most interesting for a vegetation scientist.
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Broster, Bruce E., and Pamela J. Dickinson. "Late Wisconsinan and Holocene development of Grand Lake Meadows area and southern reaches of the Saint John River Valley, New Brunswick, Canada." Atlantic Geology 51, no. 1 (April 22, 2015): 206. http://dx.doi.org/10.4138/atlgeol.2015.007.
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<p align="LEFT">A 67 m near-continuous stratigraphic core was recovered from drilling at Grand Lake Meadows, located near the junction of Grand Lake and the Saint John River, approximately 40 km south of Fredericton, New Brunswick. From analyses of recovered samples and finite radiocarbon dating, four phases of development of the study site and surrounding environs were identified to have occurred following the Late Wisconsinan glacial maximum. Phase I, related to the formation of the DeGeer Sea, commenced more than 15 000 calyBP from deglaciation accompanied by marine transgression. Phase II began ~14 000 calyBP and continued until approximately ~8000 calyBP during which time there was major isostatic readjustment in the region and formation of a stratified, mostly brackish, ancestral Grand Lake and transformation into a mostly freshwater, Lake Acadia. Phase III began shortly after 8000 calyBP and continued until after 3000 calyBP accompanied by return of the Saint John River to a fluvialdominated system after down-cutting an outlet at the Reversing Falls gorge, and draining much of Lake Acadia. During phase IV, ~3000 calyBP to present, estuarine conditions were initiated as marine water advanced upstream over the Reversing Falls, leading to the development of the modern river system and Grand Lake Meadows.</p>
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McLoughlin, Lynette. "Mangroves and Grass Swamps: Changes in the shoreline vegetation of the Middle Lane Cove River, Sydney, 1780’s – 1880’s." Wetlands Australia 7, no. 1 (January 7, 2010): 13. http://dx.doi.org/10.31646/wa.113.
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Mazurek, Kinga. "Spatial Analyses in the Research of Land Cover Changes (A Case Study)." Contemporary Trends in Geoscience 4, no. 1 (October 1, 2015): 1–13. http://dx.doi.org/10.1515/ctg-2015-0001.
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Abstract Increasing human activity significantly influences the geographic environment. The effects of excessive anthropogenic pressure are manifested by changes in land cover and in landscape structure, and land cover changes can particularly well observed in river valleys. In this study we aimed to determine the transformations of land use in 13.9 sq km of the Silesian Voivodeship in southern Poland, including parts of the city of Ruda Slaska and Mikolow County by analyzing changes in land cover that occurred from 1827-2012 and archival and contemporary topographic maps, and aerial photos were used as primary source materials. All materials were prepared with the use of Geographic Information Systems (GIS), using spatial analyses, such as kernel density and point density in order to define land cover structure changes. Results show the development of residential areas and the fragmentation of large structures that have occurred over the time period.
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García-Marín, Ramón, Cayetano Espejo-Marín, Rubén Giménez-García, and Víctor Ruiz-Álvarez. "Transformations in the Agricultural and Scenic Landscapes in the Northwest of the Region of Murcia (Spain): Moving towards Long Awaited (Un)Sustainability." Land 9, no. 9 (September 4, 2020): 314. http://dx.doi.org/10.3390/land9090314.
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Since the middle of the 20th century, irrigation in the southeast of Spain has displayed significant productive growth based on the intensive use of the scarce water resources in the area and the contribution of river flows from the hydrographic basin of the Tagus River to the hydrographic basin of the Segura River. Despite high levels of efficiency in the water use from the new irrigation systems, the water deficit has only intensified in recent years. The most dynamically irrigated areas (Campo de Cartagena, Valle del Guadalentín, Vega Alta del Segura and the southern coast of the Region of Murcia), were faced with a complex and trying future, resulting in numerous companies (agribusinesses) relocating to lease and acquire land in the northwest of Murcia to develop their intensive crops. The general objective of this article lies in the analysis of widespread landscape dynamics, and of agricultural dynamics in particular, in the rural environment of the northwest Region of Murcia (Spain). For this, an exhaustive analysis of the land cover and use transformations is carried out for the periods of time 1990–2000–2012–2018. The data studied come from the Corine Land Cover (CLC) project, carried out by the European Environment Agency (EEA). These spatial data are treated with geographical information systems (GISs) and represented by statistical and cartographic analyses and cross-tabulation matrices that indicate the dynamics of changes, loss and land gain. As the main result, we find that the areas occupied by new intensive irrigation on old rainfed farmland in the northwest Region of Murcia have increased in the last 30 years. Traditional irrigation is disappearing, and the environmental consequences (overexploitation of aquifers and decreased flows from natural sources), among others, are dire.
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Gilbert, Robert, and Joseph R. Desloges. "The late Quaternary sedimentary record of Stave Lake, southwestern British Columbia." Canadian Journal of Earth Sciences 29, no. 9 (September 1, 1992): 1997–2006. http://dx.doi.org/10.1139/e92-155.
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The postglacial sedimentary record of 59 km2 Stave Lake was investigated using 3.5 kHz subbottom profiles and cores from the sediment surface. The acoustic data show a thin cover of acoustically transparent sediment (unit 1) overlying bedrock or glacial sediment on the floor of the lake. Overlying acoustically stratified sediment is divided into unit 2, which thins from 28 m in the south of the lake to less than 12 m in the north, and unit 3, which thins from 20 m in the north to about 12 m in the south. Unit 1 is interpreted as resulting from deposition in a relatively quiet lacustrine or marine environment following retreat of Vashon glaciers about 13 ka ago. Unit 2 is ascribed to deposits of sediment in runoff to Stave Lake from the Sumas ice sheet in the Fraser Valley and connecting valleys to the Stave Basin. Following the retreat of the Sumas ice about 11 ka ago, deposition of unit 3 resulted almost entirely from sediment input from Stave River entering at the north end of the lake. Raising the lake in 1912 by damming for hydroelectric generation resulted in deposition of a thin but distinct marker horizon in the sediment, from which modern rates of accumulation averaging 3 mm/a are estimated. These are more than twice the average rates for the Holocene estimated from the total thickness of unit 3. The rates of sediment yield calculated from accumulation in Stave Lake are 4.5 × 105 kg∙km−2∙a−1 (modern) and less than 2 × 105 kg∙km−2∙a−1 (averaged over the Holocene).
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Strimbu, Bogdan M., George Mueller-Warrant, and Kristin Trippe. "Agricultural Crop Change in the Willamette Valley, Oregon, from 2004 to 2017." Data 6, no. 2 (February 7, 2021): 17. http://dx.doi.org/10.3390/data6020017.
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The Willamette Valley, bounded to the west by the Coast Range and to the east by the Cascade Mountains, is the largest river valley completely confined to Oregon. The fertile valley soils combined with a temperate, marine climate create ideal agronomic conditions for seed production. Historically, seed cropping systems in the Willamette Valley have focused on the production of grass and forage seeds. In addition to growing over two-thirds of the nation’s cool-season grass seed, cropping systems in the Willamette Valley include a diverse rotation of over 250 commodities for forage, seed, food, and cover cropping applications. Tracking the sequence of crop rotations that are grown in the Willamette Valley is paramount to answering a broad spectrum of agronomic, environmental, and economical questions. Landsat imagery covering approximately 25,303 km2 were used to identify agricultural crops in production from 2004 to 2017. The agricultural crops were distinguished by classifying images primarily acquired by three platforms: Landsat 5 (2003–2013), Landsat 7 (2003–2017), and Landsat 8 (2013–2017). Before conducting maximum likelihood remote sensing classification, the images acquired by the Landsat 7 were pre-processed to reduce the impact of the scan line corrector failure. The corrected images were subsequently used to classify 35 different land-use classes and 137 unique two-year-long sequences of 57 classes of non-urban and non-forested land-use categories from 2004 through 2014. Our final data product uses new and previously published results to classify the western Oregon landscape into 61 different land use classes, including four majority-rule-over-time super-classes and 57 regular classes of annually disturbed agricultural crops (19 classes), perennial crops (20 classes), forests (13 classes), and urban developments (5 classes). These publicly available data can be used to inform and support environmental and agricultural land-use studies.
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Tomčíková, Ivana. "Zones and segments as taxa used in the hierarchical classification of riverine landscapes: a case study of the smrečianka brook, Slovak Republic." Moravian Geographical Reports 21, no. 4 (December 1, 2013): 27–37. http://dx.doi.org/10.2478/mgr-2013-0018.
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Abstract A river is a highly complex structure and the constituent of landscape and catchment basin from which it drains water. In the holistic concept, a river is defined in mutual interactions with its surroundings as a spatial system - the riverine landscape. As a product of fluvial processes, the riverine landscape has a regular spatial hierarchical structure, which is determined by the structure of its morphology, substrate, biota, land cover and socioeconomic structures. The aim of this paper is to verify the river landscape hierarchical classification and to identify the so-called higher taxa - zones and segments in the Smrečianka valley. The main data sources were hydrological maps at 1:50 000, topographic maps at 1:10 000 and 1:25 000, GIS database levels, geological maps at 1:50 000, and the boundaries were specified by a field survey
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Isarin, R. F. B., E. Rensink, G. R. Ellenkamp, and E. Heunks. "Of Meuse and Man: the geomorphogenetic and archaeological predictive maps of the Dutch Meuse valley." Netherlands Journal of Geosciences 96, no. 2 (April 24, 2017): 183–96. http://dx.doi.org/10.1017/njg.2017.5.
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AbstractFor the first time, geomorphology and archaeology are combined for a 165 km long stretch of the Meuse river, resulting in a geomorphogenetic map (GKM) and a series of archaeological predictive maps (AVM). The maps cover the central part the Meuse valley, located in the province of Limburg between Mook in the north and Eijsden in the south. The area consists of fluvial and aeolian landforms of the Holocene Meuse floodplain and Younger Dryas aged terraces along it, spanning a period of approximately 15,000 years of landscape genesis and human habitation. The GKM more clearly discriminates between map units of Younger Dryas and early Holocene age than in previous mappings of the Meuse valley. The AVM series provide predictive information on the location of sites for four distinct consecutive archaeological periods and four main cultural themes. The maps contribute to a better understanding of landscape processes (fluvial and aeolian geomorphology and the impact of man on river behaviour), and the possibilities for human habitation and land use in prehistoric and historic times.
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Jasinski, JPP, B. G. Warner, A. A. Andreev, R. Aravena, S. E. Gilbert, B. A. Zeeb, J. P. Smol, and A. A. Velichko. "Holocene environmental history of a peatland in the Lena River valley, Siberia." Canadian Journal of Earth Sciences 35, no. 6 (June 1, 1998): 637–48. http://dx.doi.org/10.1139/e98-015.
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A 3.86 m core of peat and organic lake mud from a polygonal peatland in the Lena River valley of Siberia was radiocarbon dated and analyzed for pollen, plant macrofossils, chrysophyte stomatocysts, stable isotopes, and charcoal. At around 7200 BP, a shallow lake or open-water wetland supported diverse aquatic macrophytes. The site had transformed initially into a richer fen with Carex, Comarum palustris, and Drepanocladus and later a poorer fen with Sphagnum which persisted until around 3000 BP. Fire may have been responsible for silt being blown onto the peatland, which changed the hydrological and geochemical conditions for development of the poor fen. Ice accretion led to an increase in the height of the centre of the polygon and expansion of Sphagnum peatland . 18O values become progressively more enriched, which reflects more direct input of summer precipitation waters and less groundwater during this period. Finally, the peatland surface was elevated sufficiently to limit water and nutrient supply, thereby allowing Ericaceae and Betula to grow at the coring site. Fire burned the peatland surface and may have exaggerated the extremely slow rate of peat accumulation. Fire may also be a factor in maintaining the open Larix dahurica forest in the region today, while climate may be contributing to reducing postfire regeneration. Fire and climate together may be controlling the character and composition of forests near tree line in the Lena River valley of this part of Siberia.
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Tariq, Aqil, Jianguo Yan, Bushra Ghaffar, Shujing Qin, B. G. Mousa, Alireza Sharifi, Md Enamul Huq, and Muhammad Aslam. "Flash Flood Susceptibility Assessment and Zonation by Integrating Analytic Hierarchy Process and Frequency Ratio Model with Diverse Spatial Data." Water 14, no. 19 (September 29, 2022): 3069. http://dx.doi.org/10.3390/w14193069.
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Flash floods are the most dangerous kinds of floods because they combine the destructive power of a flood with incredible speed. They occur when heavy rainfall exceeds the ability of the ground to absorb it. The main aim of this study is to generate flash flood maps using Analytical Hierarchy Process (AHP) and Frequency Ratio (FR) models in the river’s floodplain between the Jhelum River and Chenab rivers. A total of eight flash flood-causative physical parameters are considered for this study. Six parameters are based on remote sensing images of the Advanced Land Observation Satellite (ALOS), Digital Elevation Model (DEM), and Sentinel-2 Satellite, which include slope, elevation, distance from the stream, drainage density, flow accumulation, and land use/land cover (LULC), respectively. The other two parameters are soil and geology, which consist of different rock and soil formations, respectively. In the case of AHP, each of the criteria is allotted an estimated weight according to its significant importance in the occurrence of flash floods. In the end, all the parameters were integrated using weighted overlay analysis in which the influence value of drainage density was given the highest weight. The analysis shows that a distance of 2500 m from the river has values of FR ranging from 0.54, 0.56, 1.21, 1.26, and 0.48, respectively. The output zones were categorized into very low, low, moderate, high, and very high risk, covering 7354, 5147, 3665, 2592, and 1343 km2, respectively. Finally, the results show that the very high flood areas cover 1343 km2, or 6.68% of the total area. The Mangla, Marala, and Trimmu valleys were identified as high-risk zones of the study area, which have been damaged drastically many times by flash floods. It provides policy guidelines for risk managers, emergency and disaster response services, urban and infrastructure planners, hydrologists, and climate scientists.
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Mazurek, Kinga. "Landscape structure changes in the Slepiotka River drainage basin in the period 1824-1993 (The Silesian Upland, Poland)." Contemporary Trends in Geoscience 3, no. 1 (September 1, 2014): 32–40. http://dx.doi.org/10.2478/ctg-2014-0020.
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Abstract The area of the Upper Silesian Coal Basin is the most important underground mining district in Poland. Coal mines, operating in the area since the eighteenth century, have contributed to massive transformations of the landscape structure. River valleys within range of intensive exploitation activities have been undergoing vast changes. The Slepiotka River drainage basin constitutes an interesting regional example of transformations in the river's watercourse as well as in its adjacent area. It is a left-hand tributary of the Klodnica River with a length of about 8.6 km. Changes in the landscape structure that occurred between 1824-1993 have been analyzed. The starting material consisted of topographical maps that were digitized and calibrated and served as a basis to create colorful compositions. The areas occupied by the different land cover types have been calculated, which allowed to determine their participation in the drainage basin. In about 169 years, significant changes took place in the area of research considering the share of different types of cover and land use. During this time, the river changed its course, both naturally and by human activities. Increasing urbanization and technological development contributed to the diametrical transformation of the landscape structure in the discussed area
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Tolstobrova, A. N., D. S. Tolstobrov, and O. P. Korsakova. "Environment of bottom sediments formation from the Lake Dedovo in the Voronya River valley (Kola Peninsula), according to diatom analysis (preliminary data)." Limnology and Freshwater Biology, no. 4 (2022): 1596–98. http://dx.doi.org/10.31951/2658-3518-2022-a-4-1596.
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Abstract. The study presents preliminary results of the species composition and distribution of diatoms in the core of bottom sediments of the Lake Dedovo located in the Voronya River valley (Kola Peninsula). It was determined that sedimentation occurred in the periglacial basin during Late glacial. After there was a large basin that connected with the sea, but this basin was freshwater due to the large influx of melt water. The level of this basin was at the same elevation for a long time at the beginning of the Holocene. According to preliminary radiocarbon dating, the isolation of the lake depression from a large freshwater basin occurred at the end of the Early beginning of Middle Holocene. Lake Dedovo develops as an independent basin with a diverse freshwater diatom flora after the isolation.
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Chen, Shifeng, Qifei Zhang, Yaning Chen, Honghua Zhou, Yanyun Xiang, Zhihui Liu, and Yifeng Hou. "Vegetation Change and Eco-Environmental Quality Evaluation in the Loess Plateau of China from 2000 to 2020." Remote Sensing 15, no. 2 (January 10, 2023): 424. http://dx.doi.org/10.3390/rs15020424.
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Vegetation change and ecological quality of the Loess Plateau (LP) are directly related to ecological protection and high-quality development of the Yellow River Basin. Based on LP ecological zoning and multisource remote sensing data, we analyzed vegetation change and its relationship with climate, terrestrial water storage (TWS), and land use/cover change from 2000 to 2020, using the normalized difference vegetation index (NDVI), fraction of vegetation cover (FVC), and net primary productivity (NPP). And ecological environmental quality was evaluated based on the remote sensing ecological index (RSEI). The results showed that the spatial distribution pattern of NDVI, FVC and NPP decreased from southeast to northwest in the LP as a whole. Vegetation in the LP recovered significantly, and NDVI, FVC, and NPP showed significant increases of 35.66%, 34%, and 54.69%, respectively. The average NDVI and FVC in the earth–rocky mountainous region and river valley plain region (Area D) were the highest, but the growth rate was the slowest. The average NDVI, FVC, and growth rates in the loess hilly and gully regions (Area B) were slightly higher than those in the loess sorghum gully region (Area A). The average NDVI, FVC, and NPP in the sandy land and agricultural irrigation regions (Area C) were the lowest but showed significant increase. RSEI in most LP areas changed from poor to medium, increasing by 43.45%. Precipitation is the basic factor affecting vegetation cover pattern, with the increase (40.79 mm/10a) promoting vegetation restoration in the LP. Vegetation restoration lost much TWS (−0.6 mm/month), and Area D had the highest average NDVI, FVC, and NPP but the largest TWS loss. Anthropogenic land use/cover change (LUCC) (decrease in cultivated land and unused land; increase in forest, grassland, and construction land) is the primary factor affecting LP vegetation change. This study provides a scientific reference for further vegetation restoration in the LP.
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Ishfaq Gujree, Arfan Arshad, Aijaz Reshi, and Zubair Bangroo. "Comprehensive Spatial planning of Sonamarg resort in Kashmir Valley, India for sustainable tourism." Pacific International Journal 3, no. 3 (September 30, 2020): 81–97. http://dx.doi.org/10.55014/pij.v3i3.101.
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The tourism Industry is directly linked with the environment, as tourists mainly travel to natural and green environment destinations. This study has made an attempt to demonstrate the application of Geospatial Approach in evaluation of Master Planning for Sonamarg Resort most visited tourist place of Kashmir valley. Master Plan (MP) for Tourist Resort of Sonamarg was evaluated using topographical settings (Slope, Aspects and Elevation) natural drainage and land use land cover map. Evaluation of Master plan for Sonamarg tourist resort was carried out in two ways i.e., zone vise (A, B, C and D) and slope vise. High resolution Google Earth satellite images of IKONOS were used to analyze current land use land cover in Sonamarg, which are classified into 7 classes. ASTER DEM was used to prepare the slope, elevation and drainage maps. RETScreen Expert was used to get the climate data from NASA to correlate it with the Tourist inflow months. Results indicated that “Zone A” may exhibit conversion from pastures and built up into mixed zone and village settlement; “Zone B” from agriculture to riverfronts; “Zone C” from pasture land to golf course and camping areas; “Zone D” from built up, pastures and recreations sites to golf lodges and facilities areas. Slope vise evaluation indicated that forest should be on higher slope, recreational tourist including Golf Course, River Front and Organized Parks on the moderate slope while built up on the lower slope. The Rapid settlement expansion is seen as one of the potential threats to sustainable development and settlement planning coupled with effective resource utilization and allocation of infrastructure initiatives are other key concerns.
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Hassen, Getahun, Amare Bantider, Abiyot Legesse, Malesu Maimbo, and Dereje Likissa. "Land Use and Land Cover Change for Resilient Environment and Sustainable Development in the Ethiopian Rift Valley Region." Environmental Protection and Natural Resources 32, no. 2 (June 1, 2021): 24–41. http://dx.doi.org/10.2478/oszn-2021-0007.
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Abstract Land use and land cover change (LULCC) are the result of different interacting socio-economic and environmental causes and consequences that have been known since the beginning of agriculture. The study intended to explore the implications and drivers of LULCC in the Ethiopian rift valley region of Gidabo river sub basin from 1986 to 2019. The researchers have triangulated the data from Landsat 5 (™), and Landsat 8 (OLI) with data obtained from key informants, focus groups and field observation, which is helpful to determine the interaction between the environment and the community. It is also important to mitigate environmental disaster (erosion, landslides, and climate change) and sustainable utilization of natural resources. The LULCC of the past 33 years implied that about 58.4 % of the area was changed to other Land use land cover (LULC) classes. This refers to the fact that about 14% of agroforestry, 2% of the settlement, 1.1% of the forest, and 1% of bare land were expanded at the expense of 10.3% of shrub/woodland, 6.3 % of grassland, and 1% of cropland classes. Therefore, as a result, the highest land cover (46.7%) was observed on the agroforestry system. Participants in group discussion and informant interviews attributed the expansion of agroforestry to the drivers, such as population density, cultural values (Songo, Babbo), traditional beliefs, land policy, and the insecurity resulting from climate change. Whereas, the drivers related to unproductive land, resettlement, urbanisation, and lack of agricultural inputs were considered as threats that will adversely affect the agroforestry system of the area. The study concluded that the high expansion of the agroforestry system has significant contribution to achieve a resilient environment and sustainable development, which integrates the socio-economic and environmental needs of the community. But greater attention should be given to the changes observed in shrub/woodland, grassland, and bare land to enhance environmental protection.
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Williams, Martin A. J. "A river flowing through a desert: late Quaternary environments in the Nile basin – current understanding and unresolved questions." Journal of Palaeosciences 70, no. (1-2) (September 10, 2021): 267–88. http://dx.doi.org/10.54991/jop.2021.22.
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Late Quaternary environments in the Nile Basin reflect the influence of the African summer monsoon upon plant cover, sediment yield and flood discharge in the Ethiopian and Ugandan headwaters of the Nile. Intervals of prolonged and very high Nile flow coincide with times of stronger summer monsoon and have been dated using a combination of 14C, OSL and 10Be methods. Periods of high Nile flow into the eastern Mediterranean coincide with the formation of highly organic sedimentary layers termed sapropels. Ages obtained so far for these times of sustained middle to late Pleistocene high flow in the Blue and White Nile are broadly coeval with sapropel beds S8 (ca 217 ka), S7 (ca 195 ka), S6 (ca 172 ka), S5 (ca 124 ka), S4 (ca 102 ka) S3 (ca 81 ka), S2 (ca 55–50 ka) and S1 (10–6.5 ka). Sapropel 5 (ca 124 ka) was synchronous with extreme Blue Nile floods and the formation of the 386 m lake in the lower White Nile Valley, as well as with a prolonged wet phase in the eastern Sahara. Fluctuations in Nile flow and sapropel formation reflect the influence of the precessional cycle upon the East African monsoon.
Between 75 ka and 19 ka the climate in the Nile headwaters region became progressively colder and drier. During the Last Glacial Maximum, Lake Tana in Ethiopia and Lake Victoria in Uganda became dry, flow in the White Nile was reduced to a trickle, and the Blue Nile and Atbara became highly seasonal bed–load rivers. The return of the summer monsoon at 14.5 ka ushered in extreme Blue Nile floods, widespread flooding across the Nile Basin and the formation of the 382 m lake in the lower White Nile Valley. There was a brief return to aridity during the Younger Dryas (12.8–11.5 ka), after which the climate again became wetter and widespread flooding in the Nile Valley resumed. The early Holocene floods were later followed by incision and creation of the modern relatively narrow flood plain.
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Riley, S. J., and R. G. Banks. "The role of phosphorus and heavy metals in the spread of weeds in urban bushlands: an example from the Lane Cove Valley, NSW, Australia." Science of The Total Environment 182, no. 1-3 (April 1996): 39–52. http://dx.doi.org/10.1016/0048-9697(95)05033-7.
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Hudson, Paul F., René R. Colditz, and Miguel Aguilar-Robledo. "Spatial Relations Between Floodplain Environments and Land Use – Land Cover of a Large Lowland Tropical River Valley: Pánuco Basin, México." Environmental Management 38, no. 3 (September 2006): 487–503. http://dx.doi.org/10.1007/s00267-003-0157-4.
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Ebert, Claire E., Julie A. Hoggarth, and Jaime J. Awe. "Integrating Quantitative Lidar Analysis and Settlement Survey in the Belize River Valley." Advances in Archaeological Practice 4, no. 3 (August 2016): 284–300. http://dx.doi.org/10.7183/2326-3768.4.3.284.
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AbstractAccurate and high-resolution airborne light detection and ranging (lidar) data have become increasingly important for the discovery and visualization of complete archaeological settlement systems in the Maya Lowlands. We present the results of systematic quantitative analysis of lidar data and ground verification for the major centers of Cahal Pech, Baking Pot, and Lower Dover in the Belize Valley. The Belize Valley is characterized by high density populations living in growing modern towns and villages, and by large-scale agricultural production. This urban environment presents a challenge to reconnaissance efforts since modern construction and agricultural activities have destroyed ancient ruins and created new vegetation patterns. Lidar data was analyzed within a GIS using the Topographic Position Index (TPI) to identify the location of possible archaeological remains. Small-scale, site-level TPI analysis helped identify more detailed archaeological features including small house mounds, terraces, and ditches. Results indicate that lidar data recorded for areas with dense vegetation (e.g., low brush and secondary regrowth) may be less reliable for identification of archaeological remains. The quantitative and qualitative differences between spatial analyses and pedestrian survey results among land cover types indicate that traditional settlement pattern study methods, including pedestrian survey, remain vital to ground-truthing all types of spatial data.
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Reheis, Marith C., John Caskey, Jordon Bright, James B. Paces, Shannon Mahan, and Elmira Wan. "Pleistocene lakes and paleohydrologic environments of the Tecopa basin, California: Constraints on the drainage integration of the Amargosa River." GSA Bulletin 132, no. 7-8 (November 21, 2019): 1537–65. http://dx.doi.org/10.1130/b35282.1.
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Abstract The Tecopa basin in eastern California was a terminal basin that episodically held lakes during most of the Quaternary until the basin and its modern stream, the Amargosa River, became tributary to Death Valley. Although long studied for its sedimentology, diagenesis, and paleomagnetism, the basin’s lacustrine and paleoclimate history has not been well understood, and conflicting interpretations exist concerning the relations of Tecopa basin to the Amargosa River and to pluvial Lake Manly in Death Valley. Previous studies also did not recognize basinwide tectonic effects on lake-level history. In this study, we focused on: (1) establishing a chronology of shoreline deposits, as the primary indicator of lake-level history, utilizing well-known ash beds and new uranium-series and luminescence dating; (2) using ostracodes as indicators of water chemistry and water source(s); and (3) correlating lake transgressions to well-preserved fluvial-deltaic sequences. During the early Pleistocene, the Tecopa basin hosted small shallow lakes primarily fed by low-alkalinity water sourced mainly from runoff and (or) a groundwater source chemically unlike the modern springs. The first lake that filled the basin occurred just prior and up to the eruption of the 765 ka Bishop ash during marine isotope stage (MIS) 19; this lake heralded the arrival of the Amargosa River, delivering high-alkalinity water. Two subsequent lake cycles, coeval with MIS 16 (leading up to eruption of 631 ka Lava Creek B ash) and MIS 14 and (or) MIS 12, are marked by prominent accumulations of nearshore and beach deposits. The timing of the youngest of these three lakes, the High lake, is constrained by a uranium-series age of ca. 580 ± 120 ka on tufa-cemented beach gravel and by estimates from sedimentation rates. Highstand deposits of the Lava Creek and High lakes at the north end of the basin are stratigraphically tied to distinct sequences of fluvial-deltaic deposits fed by alkaline waters of the Amargosa River. The High lake reached the highest level achieved in the Tecopa basin, and it may have briefly discharged southward but did not significantly erode its threshold. The High lake was followed by a long hiatus of as much as 300 k.y., during which there is evidence for alluvial, eolian, and groundwater-discharge deposition, but no lakes. We attribute this hiatus, as have others, to blockage of the Amargosa River by an alluvial fan upstream near Eagle Mountain. A final lake, the Terminal lake, formed when the river once again flowed south into Tecopa basin, but it was likely short-lived due to rapid incision of the former threshold south of Tecopa. Deposits of the Terminal lake are inset below, and are locally unconformable on, deposits of the High lake and the nonlacustrine deposits of the hiatus. The Terminal lake reached its highstand at ca. 185 ± 21 ka, as dated by infrared-stimulated luminescence on feldspar in beach sand, a time coincident with perennial lake mud and alkaline-tolerant ostracodes in the Badwater core of Lake Manly during MIS 6. A period of stillstand occurred as the Terminal lake drained when the incising river encountered resistant Stirling Quartzite near the head of present-day Amargosa Canyon. Our studies significantly revise the lacustrine and drainage history of the Tecopa basin, show that the MIS 6 highstand was not the largest lake in the basin as previously published (with implications for potential nuclear waste storage at Yucca Mountain, Nevada), and provide evidence from shoreline elevations for ∼20 m of tectonic uplift in the northern part of the basin across an ENE-trending monoclinal flexure.
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Worku, F. F., M. Werner, N. Wright, P. van der Zaag, and S. Demissie. "Flow regime change in an Endorheic basin in Southern Ethiopia." Hydrology and Earth System Sciences Discussions 11, no. 1 (January 29, 2014): 1301–42. http://dx.doi.org/10.5194/hessd-11-1301-2014.
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Abstract. Endorheic basins, often found in semi-arid and arid climates, are particularly sensitive to changes in climatological fluxes such as precipitation, evaporation and runoff, resulting in variability of river flows as well as of water levels in end-point lakes that are often present. In this paper we apply the Indicators of Hydrological Alteration (IHA) to characterise change to the natural flow regime of the Omo-Ghibe basin in Southern Ethiopia. This endorheic basin is considered relatively pristine, with the basin being the main source of flow to Lake Turkana, the end-point lake in the East-African rift valley. The water level in Lake Turkana shows significant fluctuation, but an increasing trend can be observed over the past 20 yr. The reasons are currently not well understood. Of the five groups of metrics in the IHA, only those related to magnitude were found to show significant trends, with the main trend being the increase of flow during the dry season. This trend was not reflected in climatological drivers such as rainfall, evaporation, and temperature (which shows an increasing trend), but rather is attributed to the substantial changes in Land Use and Land Cover (LULC) in the basin. The impact on the basin hydrology is apparent mainly in the more humid part of the basin. The significant shift from forest and woodland to grassland and cropland results in a decrease of actual evaporation and subsequent increase in (dry season) runoff. The long term trend of the increasing levels in lake Turkana are related to these trends in dry season flows, while shorter term fluctuations of the lake levels are attributed primarily to anomalies in consecutive wet and dry season rainfall.
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Telford, Richard J., and Henry F. Lamb. "Groundwater-Mediated Response to Holocene Climatic Change Recorded by the Diatom Stratigraphy of an Ethiopian Crater Lake." Quaternary Research 52, no. 1 (July 1999): 63–75. http://dx.doi.org/10.1006/qres.1999.2034.
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The diatom stratigraphy of a 23-m sediment core from Lake Tilo, a maar lake in the Ethiopian Rift Valley, provides a 10,000-yr record of lake salinity and trophic status. Until 5500 14C yr B.P., the phytoplankton was dominated by Aulacoseira granulata, with only minor changes in the abundance of other diatoms; the lake was over 50 m deep, eutrophic, and oligosaline. At 5500 yr B.P., geothermal groundwater inflow, inferred from calcite and silica deposition rates, declined abruptly, and the lake became more oligotrophic, as indicated by a rapid rise in Cyclotella stelligera. About 4500 yr B.P., lake salinity began to increase, reaching approximately its present state ca. 2500 yr B.P., but with a temporary reversal to lower salinity at 4000–3500 yr B.P. The record shows no evidence of salinity increases equivalent to early Holocene low stands of the larger river-fed Rift Valley lakes, probably because of high rates of geothermal groundwater influx. It responded to reduced rainfall at 4500 yr B.P., when levels of the larger lakes also fell, because geothermal groundwater flux had diminished 1000 year earlier, independently of climate. Because geothermal groundwaters can form a significant proportion of a crater lake's hydrological budget and dominate its salinity budget, these results show that variable geothermal groundwater flux can override lake hydrochemical response to climate change. Palaeoclimatic interpretation of palaeosalinity proxies from the sediments of volcanic crater lakes should be approached with caution.