Letteratura scientifica selezionata sul tema "Rivers"

Integrated development and management of international rivers requires objectively international river’s information integration.Based on the analysis of the connotation and requirement of integrated development and management of international rivers, the article point out that the information integration is the basis and means of the of integrated development and management of international rivers. And then analyze how to utilize modern information technology to build information management system of international river to achieve international river’s information sharing and scientific decision-making. Finally, analyze the factors affecting international river information integration.

The river museum in Banjarmasin is a place to capture the existence of rivers in Banjarmasin. The existence of rivers decrease in function and existence until it turns into a dead river. The river's existence is influenced by river culture. River culture is formed by people whose lives depend on rivers. Therefore, to preserve the information related to this matter, efforts are made by preserve and communicate it to the public by create a river museum.To create a river museum, the point of view concept is used which tells the museum narrative based on time, place, and actor. This concept is supported by the application of the sense of place method. Thus, river museums can make visitors educated and empathize with rivers in Banjarmasin.

The geological diversity of the Amazon Basin, as well as the pluvial regime, influences the characteristics of the waters. To know the water types of the rivers of the Amazon basin, 288 superficial water samples were collected, 94 of them along the Amazon River and 194 in their tributaries, from March 2009 to September 2012. The physical, chemical, and physicochemical properties were analyzed. Rivers with pH between 6.5 and 7.6 and electrical conductivity (40.00 - 80.00 μS cm-1) are water bodies that are influenced by the Andean region (e.g., the Amazon River and some of its right bank tributaries). On the other hand, the rivers with pH in the range of 3.5 to 5.5 and conductivity <30.00 μS cm-1, which are Amazon River’s left bank tributaries, reflect the characteristics of the Guiana Shield. The rivers with pH (6.0 to 7.0), low ionic charge, and conductivity <40.0 μS cm-1, such as the lower Amazon River’s right bank tributaries (Tapajos and Xingu) which are influenced by the Central Brazilian Shield, and also the middle/upper Amazon River’s right bank tributaries (Tefé, Coari and Jutaí).

Abstract The timing of river entry in the Atlantic salmon is known to depend on genetic, demographic and environmental factors, but little is known about the relative magnitude of among population and among year variation and covariation in this respect in natural state Atlantic salmon rives. To investigate this, variability in the timing of river entry in three historical Finnish Atlantic salmon populations were analyzed using salmon trap data collected during 1870 - 1902. The analyses reveled that 1) the timing of river entry differed substantially and consistently among the rivers, and that 2) variation among the rivers was much larger than variation among years. Annual variations were not explained by regional environmental conditions, whereas in one river the timing of the local flood peak was a significant predictor of the timing of river entry. Differences in the timing of salmon entry to geographically closely situated rivers suggests that a regionally fixed opening date for coastal fisheries might not be the best management strategy as it may lead to uneven exploitation of salmon populations from different rivers

Maintaining healthy river ecosystem is essential both from aquatic biodiversity conservation perspective as well as for the socio-cultural and economic development of nations all over the world. Many rivers in Nepal have largely been modified with the purpose of supplying drinking water, irrigating agricultural lands, producing hydro-electricity, and operating water mills. During the process, rivers are channelized and the river bed materials are removed. Such activities of river bed excavation have changed both the natural flow regimes and morphological characteristics of rivers. Studies on the impacts caused by such stressors on river ecosystems are lacking in the context of Nepalese river systems. Therefore we have assessed how these stressors might change the faunal composition of benthic macroinvertebrates in headwaters of the Western region of Nepal. The study was conducted in the headwaters of rivers of Mahakali and Karnali rivers. Habitat specific benthic macroinvertebrates were sampled from 33 sites seasonally in the year 2016 and 2017. Physical characteristics of rivers including river bed composition, water abstractions and other local stressors including waste dumping and washing-bathing were noted in the field. The study showed that macroinvertebrates community structures were significantly different in the habitat modified sites compared to reference sites. In general, abstracted sites coupled with river bed removals were found to be colonized by fewer taxa with high dominance of pool preference biota such as genera of Mayflies (Torleya spp., Caenis spp., Choroterpes spp.) and families of true flies (Chironomidae and Ceratopogoniidae). Macroinvertebrates’ abundance was significantly lower in the habitat modified sites. This study envisages that maintaining river’s habitats with minimal flows all round year could preserve ecological integrity of river systems.

A methodology for indexing river environmental condition was developed and applied to 269 subsections of national rivers located in the Republic of Korea, based on a river management perspective. The resulting index has been called the River Environment Index (REI). To develop the methodology, a total of 32 factors related to a river's environment were initially investigated, from which 16 were chosen based on their measurability, predictability, measurement regularity and obtainability. Then, using the analytical hierarchy process (AHP) and based on a survey of 62 river management experts in Korea, the weighting coefficient for each of the 16 factors was determined. Finally, the REI values were estimated by linearly combining the 16 measured factors for the 269 river subsections and mapped using a geospatial information system platform. We expect that the REI will be used to increase the efficient allocation of national budgets for environmentally-friendly river restoration projects of the country's national rivers. Through this new index, prioritization of these rivers will be made using an holistic river management perspective.

Gendol River flows from the south slope of Merapi Volcano meets Opak River to form a wider river, namely Opak River. In the upper stream of Opak and Gendol Rivers area, volcanic material accumulated from the 2010 Merapi Volcano eruption that ready to flow downstream through both rivers. The total amount of volcanic material in the Merapi’s peak area is predicted as much as 140 million cubic meters, part of it is distributed in the upper stream of both rivers. In the downstream area, the Opak River flows nearby the great Prambanan Temple and across the main road of Yogyakarta-Surakarta capital cities.To know the laharic flow disaster potential of both rivers, collecting of primary data along the river flows is needed in order to understand the characteristic and mechanism of laharic flows. DEM analysis combined with ArcGIS 9.3 tools are applied to know the additional volume of volcanic material after 2010 Merapi Volcano eruption. The triggering factor of laharic flows in the study area including the runoff, soil water saturation rate, rainfall and soil water saturation time are mathematically calculated based on data analysis on soil mechanics.Based on the calculation of thickness and distribution in the Merapi Peak area, the mass volcanic material that is ready to be transported as the laharic flows through Gendol and Opak Rivers is around 14,745,496 m3. The volcanic material can transform into laharic flows by initial runoff if the soil water saturation column reach at least 5.96 m. With the rainfall average in the southern part of Merapi Volcano is 17.32 mm/day, that saturation value can be reached by 21.8 hours in the upper stream area and 17.67 hours in the lower part area. If the laharic flows occurred, the damage would happen in villages along the rivers, Prambanan Temple, and Opak River’s Bridge connecting Yogyakarta-Surakarta main road.

Today’s ecology is erected with miscellaneous framework. However, numerous sources deteriorate it, such as urban rivers that directly cause the environmental pollution. For chemical pollution abatement from urban water bodies, many techniques were introduced to rehabilitate the water quality of these water bodies. In this research, Bacterial Technology (BT) was applied to urban rivers escalating the necessity to control the water pollution in different places (Xuxi River (XXU); Gankeng River (GKS); Xia Zhang River (XZY); Fenghu and Song Yang Rivers (FSR); Jiu Haogang River (JHH)) in China. For data analysis, the physiochemical parameters such as temperature, chemical oxygen demand (COD), dissolved oxygen (DO), total phosphorus (TP), and ammonia nitrogen (NH3N) were determined before and after the treatment. Multicriteria Decision Making (MCDM) method was used for relative significance of different water quality on each station, based on fuzzy analytical hierarchy process (FAHP). The overall results revealed that the pollution is exceeding at “JHH” due to the limit of “COD” as critical water quality parameter and after treatment, an abrupt recovery of the rivers compared with the average improved efficiency of nutrients was 79%, 74%, 68%, and 70% of COD, DO, TP, and NH3N, respectively. The color of the river’s water changed to its original form and aquatic living organism appeared with clear effluents from them.

Temporary rivers and streams that naturally cease to flow can be found on every continent. Many others that were once perennial now also have temporary flow regimes due to the effects of water extraction or changes in land-use and climate, while others that used to run dry no longer do so due to water releases and waste water discharges. The dry beds of temporary rivers are an integral part of river landscapes and have: a role as seed and egg banks for aquatic biota; a unique diversity of aquatic, amphibious and terrestrial biota; a role as dispersal corridors; as temporal ecotones linking wet and dry phases; and as sites for the storage and processing of organic matter and nutrients. They also have a societal values, such as significance in human language and culture; agricultural uses; sources of sand and gravel for building purposes; and as places for recreation. ‘Traditional’ conceptual models of riverine ecosystem structure and function do not consider the dry phase. As a consequence, these models are incomplete and are thus not fully applicable to many parts of the world where temporary rivers are common and the dry phase is significant.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

Over the past 200 years, rivers in industrialized countries have been significantly altered by human interventions such as channelization, hydropower development, and sediment mining causing observable biogeomorphological changes. In the European Alpine region, many large rivers have been impounded and channelized, yet few studies have conducted in-depth research on the temporal patterns of the causes and trajectories of these biogeomorphological responses, in comparison to rivers that can adjust their planform. Moreover, it is well-known that within channelized rivers alternating bars may appear due to an instability of the riverbed, but the development and influence of vegetation on such bars, its feedbacks on the morphodynamics of the bars and the degree to which these mutual interaction processes responds to anthropic stressors related to alterations in the flow and sediment supply regimes has received little attention. The present research aims to disentangle the mechanisms that may determine dramatically diverging biogeomorphological trajectories in regulated Alpine rivers. It further intends to identify the underlying relations of the triad that connects vegetation – sediment – flow regime and its feedbacks in regulated, channelized, rivers with vegetated bars. The methodology comprises an interdisciplinary approach which combines field and historical investigations with theoretical predictions, and integrates a variety of spatial and temporal scales and different levels of detail in characterising processes. Two case studies in the Alpine region (the Isère river in southeast France and the Noce river in northeast Italy) were selected for a quantitative, historical analysis of the bio-morphological trajectories using remotely sensed data to investigate the apparent responses to human-induced modifications of natural processes. Both rivers have been heavily impacted, with a notable increase of human stressors since the mid-20th century which can be associated with the transition of both systems from an initial, stable dynamic state characterized by bars having only sparse colonizing vegetation with a frequent turnover to a new, apparently stable state characterised by reduced morphodynamics and an increased vegetation cover in recent decades. The Isère river, which underwent a shift from unvegetated, migrating bars to vegetated, stable bars, was further explored with a hydromorphodynamic modelling approach to investigate historical changes in riparian vegetation recruitment and survival related to changes in the flow regime. The Windows of Opportunity model was successful at revealing temporal changes in recruitment conditions in response to flow regime alterations. Further results indicated a reduction in relevant high flow events that might be competent to induce large bar migration in the system. Alterations of the flow regime are assumed to have played a major role in vegetation encroachment directly by affecting vegetation recruitment through reduced flow disturbances and indirectly inducing modifications of bar morphodynamics. Field observations of root development were also made on the Noce and Isère rivers, focusing on two species Salix alba and Phalaris arundinacea, with the aim of improving understanding of the role of roots on the presence and movement of vegetated bars. When comparing results from different sites, more predictable linear relationships between root properties and depth below the ground surface were associated with stronger flow regulation. Bar morphology (surface elevation or depth of sedimentation and sediment calibre) and flow regime were found to be the main drivers of root architecture. Furthermore, roots were found to have an important role in the stabilization of the bars with the ability to stabilise fine sediments trapped by the plant’s canopy during phases of bar aggradation. To understand the current state of channelized Alpine rivers, which often show diverging biogeomorphic features, it is necessary to understand the underlying interactions between flow, sediment, and vegetation dynamics. Only through investigating the historical biomorphological evolution of rivers and the main drivers of that evolution it is possible to design measures that can be effective in rehabilitating desired ecosystem functions that have been markedly modified by those state transitions. In summary, this study has provided novel, quantitative insights about the complexity of flow – vegetation – morphology interactions occurring in channelized river systems in relation to anthropogenic stressors causing alteration in their flow and sediment supply regimes. By integrating different approaches, this study has shown how these river systems can be highly sensitive to even small changes in the anthropogenic stressors, depending on the stage in their evolutionary trajectory, which is crucial to be detected to support the development of sustainable management strategies aimed at restoring or improving target riverine functions and processes.

Over the past 200 years, rivers in industrialized countries have been significantly altered by human interventions such as channelization, hydropower development, and sediment mining causing observable biogeomorphological changes. In the European Alpine region, many large rivers have been impounded and channelized, yet few studies have conducted in-depth research on the temporal patterns of the causes and trajectories of these biogeomorphological responses, in comparison to rivers that can adjust their planform. Moreover, it is well-known that within channelized rivers alternating bars may appear due to an instability of the riverbed, but the development and influence of vegetation on such bars, its feedbacks on the morphodynamics of the bars and the degree to which these mutual interaction processes responds to anthropic stressors related to alterations in the flow and sediment supply regimes has received little attention. The present research aims to disentangle the mechanisms that may determine dramatically diverging biogeomorphological trajectories in regulated Alpine rivers. It further intends to identify the underlying relations of the triad that connects vegetation – sediment – flow regime and its feedbacks in regulated, channelized, rivers with vegetated bars. The methodology comprises an interdisciplinary approach which combines field and historical investigations with theoretical predictions, and integrates a variety of spatial and temporal scales and different levels of detail in characterising processes. Two case studies in the Alpine region (the Isère river in southeast France and the Noce river in northeast Italy) were selected for a quantitative, historical analysis of the bio-morphological trajectories using remotely sensed data to investigate the apparent responses to human-induced modifications of natural processes. Both rivers have been heavily impacted, with a notable increase of human stressors since the mid-20th century which can be associated with the transition of both systems from an initial, stable dynamic state characterized by bars having only sparse colonizing vegetation with a frequent turnover to a new, apparently stable state characterised by reduced morphodynamics and an increased vegetation cover in recent decades. The Isère river, which underwent a shift from unvegetated, migrating bars to vegetated, stable bars, was further explored with a hydromorphodynamic modelling approach to investigate historical changes in riparian vegetation recruitment and survival related to changes in the flow regime. The Windows of Opportunity model was successful at revealing temporal changes in recruitment conditions in response to flow regime alterations. Further results indicated a reduction in relevant high flow events that might be competent to induce large bar migration in the system. Alterations of the flow regime are assumed to have played a major role in vegetation encroachment directly by affecting vegetation recruitment through reduced flow disturbances and indirectly inducing modifications of bar morphodynamics. Field observations of root development were also made on the Noce and Isère rivers, focusing on two species Salix alba and Phalaris arundinacea, with the aim of improving understanding of the role of roots on the presence and movement of vegetated bars. When comparing results from different sites, more predictable linear relationships between root properties and depth below the ground surface were associated with stronger flow regulation. Bar morphology (surface elevation or depth of sedimentation and sediment calibre) and flow regime were found to be the main drivers of root architecture. Furthermore, roots were found to have an important role in the stabilization of the bars with the ability to stabilise fine sediments trapped by the plant’s canopy during phases of bar aggradation. To understand the current state of channelized Alpine rivers, which often show diverging biogeomorphic features, it is necessary to understand the underlying interactions between flow, sediment, and vegetation dynamics. Only through investigating the historical biomorphological evolution of rivers and the main drivers of that evolution it is possible to design measures that can be effective in rehabilitating desired ecosystem functions that have been markedly modified by those state transitions. In summary, this study has provided novel, quantitative insights about the complexity of flow – vegetation – morphology interactions occurring in channelized river systems in relation to anthropogenic stressors causing alteration in their flow and sediment supply regimes. By integrating different approaches, this study has shown how these river systems can be highly sensitive to even small changes in the anthropogenic stressors, depending on the stage in their evolutionary trajectory, which is crucial to be detected to support the development of sustainable management strategies aimed at restoring or improving target riverine functions and processes.

The present research studies fluvial processes –water and sediment flows – that define the shape of an alluvial channel. The relationship between forms and processes is complex because they are interrelated: the channel shape influences the water flow which drives the sediments movement on the channel bed that modifies the channel form, closing a circle. Although, the objective of the work is a very old question in fluvial studies, to explain the shape of rivers in terms of external controls and internal processes, the problem has not been solved yet and this study provies new elements for its solution. The start of the quest for linking process and forms can be found in the development of regime theories which consists of a set of equations to estimate the width, depth and slope of a stable channel if liquid discharge and sediment supply are known. Regime theories were created in the XIX century within the context of hydraulic engineering in order to design stable irrigation canals (e.g. Kennedy, 1895; Lacey, 1930; Lane, 1955). Leopold and Maddock (1953) introduced the quantitative concept of hydraulic geometry into the context of fluvial geomorphology and showed that alluvial rivers adjust both their slope and channel in order to be in equilibrium for a certain representative discharge. The first studies were eminently empiric, hence there has also been an intense theoretical work focused on explaining regime relations. Parker (1978) demonstrated the importance of bank erodibility, and the need of using improved hydraulic models to calculate the shear stress distribution on irregular cross-sections. Alternative conceptual approaches have been used to explore geometrical channel properties. Langbein & Leopold (1962) took advantage of thermodynamic principles to suggest that the distribution of energy in a river system tends towards the most probable state. After this first pioneering work, further so-called “extremal” hypotheses were proposed such as: minimum unit stream power (Yang and Song, 1979), minimum stream power (Chang, 1980), minimum energy dissipation rate (Brebner and Wilson, 1967; Yang et al., 1981), maximum sediment transport rate (White et al., 1982), maximum friction factor (Davies and Sutherland, 1983) and maximum resistance to flow (Eaton et al, 2004). Millar & Quick (1993) and Millar (2005) proposed models that take into account the bank strength, a distinctive condition not considered in previous works. Because of their lack of physical-based principles, extremal hypothesis approaches have been extensively criticized (Ferguson, 1986; Parker et al., 2007). Defenders claimed their validity based on the principle of least action (Nanson and Huang, 2008) or on the opposed feedback processes acting at the cross-section scale (Eaton et al., 2006). Regime models usually consider three degrees of freedom (width, depth, and slope) and four external control variables (liquid discharge, sediment supply, bed grain size, and bank strength). However, these variables reflect geomorphic processes acting at different temporal and spatial scales (Weichert et al. 2009) a crucial aspect not considered in regime models. The first part of the research was then dedicated to review and discuss theoretical issues inherent to the representation of fluvial systems and to regime theories. As a result, I proposed that a) physical laws and constrains describe the behaviour of a population of river reaches, instead of describing the exact processes within a single river reach; and b) each object contained in the population has uncertain boundaries (width, depth) and uncertain properties (median grain size, slope, bankfull discharge). Regime theories were classified according to the number of dimensions and the way of modeling the fluvial system. In this way, light was shed on the current debate about the validity of extremal hypothesis theories. The second part of the research focus on the study of the river-populations, consisting on the comparison of natural river reaches in Patagonia Region (Argentina) and river reaches disturbed due to human activities in Northern Italy. Extensive field measurements were conducted in Italy and Argentina; five river reaches were surveyed in Italy (belonging to Brenta, Piave and Cordevole rivers, in the Veneto Region) and ten river reaches in Argentina (in the mountain range of Central Patagonia). River reaches were chosen for their morphological homogeneity and for having at least 20 years of continuous flow record. In Argentina systematic measurements began by the middle of twentieth century. For the selected gauge stations records covered a time span ranging from 25 to 63 years. in Italy, water discharge has been measured at the Brenta River since 1924 at the Barzizza station and for the Piave River, flow records are derived from three gauging stations at Segusino, Belluno y Perarolo. Reaches were selected for being completely alluvial and having at least one bank free to evolve. In some cases a thick vegetation was growing in the banks, and in few cases one of the banks was protected with groynes. All selected reaches started and finish at riffles and extended along a whole wave length comprising three riffles and two pools. Then extensive and detailed field information was used to compare natural rivers in Patagonia and disturbed in Italy. The comparison was aimed to assess the stability state of Italian rivers, considering the properties of rivers in Patagonia as a reference of stable state. Then, following the concept of spatial scales and channel response proposed by Weichert et al. (2009), the consequences in regime models of considering the hypothesis that, while channel width and depth adjust quickly to changes in water and sediment supply, reach slope requires longer time spans, was explored. Three models, all of them incorporating a bank stability criterion, were considered in this study. In order to evaluate the performance of models introducing the slope as an independent variable, two modifications to previous models were proposed. The study also used published hydraulic geometry of gravel-bed rivers in other geographical regions (92 streams reaches) and laboratory data (36 small stream). Finally, Millar’s (2005) regime model was used to explain recent morphological changes and potential recovery in the Piave and Brenta rivers. The third and last part of the thesis was dedicated to the development and test of a 2D fully processes-based model, which was named LICAN-LEUFU. This part of the study was based on the assumption that “the channel morphology is driven by and is a consequence of within-channel processes; and a two-spatial-dimensions and depth-averaged model describes best the morphology of the channel”. The first part states that processes are the responsible of observed forms, which is the position hold in this study with regards to the debate on regime models. However, it should not be interpreted that extremal hypotheses are not necessary for predicting the channel shape. Extremal hypotheses express the behaviour at the reach scale while here, reach-scale features are explained by processes acting at a lower spatial scale. The second part means that the 2D model should do better in predicting channel morphology than 1D or aggregated models, i.e, the model is capable of predicting the reach-average form (width and depth) and also within channel morphology (pools and riffles) that are not within the capabilities of 1D or aggregated models. The model was tested in three different ways. The first test was based on flume measurements conducted at the facilities of the University of Hull. The model was used to predict the response of a laboratory flume that developed a static armour under conditions of sediment starvation. The observational consequences consisted on the bed change, surface grain size distribution change, outgoing sediment transport (bulk and grain size distribution). The second test was a middle-term simulation in which the model had to predict the shape of Azul River providing the actual water discharges, bed material, and estimated sediment supply, i.e., it was an application of the 2D model in the context of regime theories. The last test concerned the application of the model to a field case study: the Brenta River. The model was loaded with the initial morphology and surface grain size distribution and a series of runs were performed imposing the recorded discharges. Model predictions were compared against the final DTM (digital terrain model) and then used for assessing the possible evolution of the reach
La presente ricerca studia i processi –i flussi dell’acqua e dei sedimenti- che definiscono la forma dei corsi alluviali. Il rapporto tra forme e processi si presenta molto complesso perché queste aspetti interagiscono mutuamente: la forma dell’alveo influisce il flusso delle acque che guida il moto delle particelle sul fondo ed, a sua volta, modifica la forma del canale. Questo studio riprende un vecchio argomento negli studi fluviali, quello di spiegare la forma dei corsi’acqua come risposta a certi controlli esterni e processi interni. Tuttavia, il problema non è risolto e questo studio apporta nuovi elementi. Il punto di partenza nello studio del rapporto tra forme e processi si trova nelle teorie di regime che consistono in un insieme di equazioni per estimare la larghezza, profondità e pendenza di un corso d’acqua in equilibrio, quando la portata liquida ed il apporto di sedimenti sono conosciuti. Le teorie di regime sono state create nel secolo XIX inquadrate nell’ambito dell’ingegneria idraulica per la progettazione di canali di irrigazioni (Kennedy, 1895; Lacey, 1930; Lane, 1955). Leopold and Maddock (1953) introdussero il concetto di geometria idraulica nella geomorfologia fluviale e dimostrarono che i corsi’acqua modificano la pendenza nonché la sezione trasversale per raggiungere lo stato di equilibrio per una portata rappresentativa. I primi studi sono stati empirici, quindi un intenso lavoro teorico è stato svolto ai fini di spiegare le equazioni di regime. Parker (1978) dimostrò l’importanza di considerare la resistenza delle sponde nelle formulazioni nonché di usare modelli idraulici sofisticati per calcolare correttamente la distribuzione dello sforzo di taglio sul letto dell’alveo. Una strategia alternativa è stata applicata per esplorare le proprietà geometriche dei canali. Langbein e Leopold (1962) considerarono i principi della termodinamica e suggerirono che la distribuzione dell’energia in un fiume tendeva verso lo stato piu probabile. Questo lavoro aprì un cammino teorico e poi altre teorie, chiamate “extremal hypothesis”, sono state proposte: minima potenzia unitaria della corrente (Yang e Song, 1979), minima potenza della corrente (Chang, 1980), minima dissipazione di energia (Brebner and Wilson, 1967; Yang et al., 1981), massimo trasporto di sedimenti (White et al., 1982), massimo fattore di frizione (Davies e Sutherland, 1983) e massima resistenza al flusso (Eaton et al., 2004). Millar e Quick (1993) e piu recentemente Millar (2005) hanno proposto modelli che prendono in considerazione la resistenza delle sponde, un aspetto che non era stato incorporato nei precedenti lavori. Le teorie “extremal hypothesis” sono state criticate per la loro mancanza di base fisica (Ferguson, 1986; Parker et al., 2007). Tra l’altro, i difensori asseriscono la loro validità sulla base del principio di minima azione (Nanson e Huang, 2008), oppure nella esistenza di due feedback opposti che agiscono ad una scala ridota, quella della sezione trasversale (Eaton et al., 2006). Le teorie di regime normalmente considerano tre gradi di libertà (larghezza, profondità e pendenza) e quattro controlli esterni (portata liquida, apporto di sedimenti, diametro dei sedimenti, e resistenza delle sponde). Tuttavia, i parametri geometrici riflettono anche processi che aggiscono ad scale spaziale e temporali differenti (Weichert et al. 2009), un aspetto che non è stato considerato nelle teorie di regime. La prima parte della ricerca è stata orientata alla revisione e discussione dei problemi teorici connessi sia con la rappresentazione dei sistemi fluviali sia con le teorie di regime. Come risultato, ho proposto i seguenti aspetti: a) le leggi della fisica ed i vincoli invocati nelle teorie di regime descrivono il comportamento di una popolazione di fiumi invece di descrivere i processi precisi al interno di un singolo tratto fluviale; b) ogni singolo elemento della popolazione ha dei confini incerti (larghezza e profondità) ed anche delle proprietà incerte (diametro medio delle particelle nell’alveo, pendenza e portata a piene rive). Le teorie di regime sono state classificate secondo il numero di dimensioni ed il modo in cui i fiumi sono modellati. La classificazione è stata applicata alle teorie di regime per comprendere il debattito in torno alla validità delle teorie “extremal hypothesis”. La seconda parte della ricerca è indirizzata verso lo studio delle popolazioni di fiumi. Si presenta un confronto fra fiumi in stato naturale dalla Patagonia Argentina con quelli relativi ai fiumi disturbati dalle attività antropiche localizzati nella regione nordest di Italia. Sono state effettuati rilevamenti intensivi di campo in Italia ed Argentina; cinque tratti sono stati rilevati in Italia (appartenenti ai fiumi Brenta, Piave e Cordevole, tutti localizzati nella Regione del Veneto) e dieci tratti in Argentina (nelle provincie di Chubut e Rio Negro). I tratti scelti per l’indagine hanno omogeneità morfologica lungo tutto il tratto e le stazione di misure delle portate vicine hanno almeno registri di 20 anni di dati. In Argentina le misure sistematiche delle portate iniziarono verso la metà del secolo scorso e quindi ci sono circa tra 23 e 63 anni di datti nelle stazione selezionate. In Italia, le misurazioni per il fiume Brenta si trovano nella stazione di Barzizza vicina a Bassano del Grappa, che ha registri dall’anno 1924. Per quanto riguarda il fiume Piave, dati da tre stazioni sono state analizzati: Belluno, Segusino e Perarolo. I tratti selezionati sono alluviali ed al meno una delle sponde è libera di evolvere. In certi casi la vegetazione copriva una delle sponde e in pochi tratti c’èrano opere di difesa spondale. Tutti i tratti iniziano in un raschio (“riffle”) e finiscono anche in un’altro raschio, estendendosi lungo almeno una lunghezza di onda. La informazione di campo, essendo estesa e dettagliata, è stata utilizzata ai fini di confrontare i corsi naturali e disturbati. Il confronto ha permesso di valutare la stabilità raggiunta dai corsi d’acqua italiani, considerando i fiumi patagonici come riferimento dello stato di equilibrio. Inoltre, seguendo il concetto di rapporto fra scale spaziali e risposta del canale proposta dai ricercatori Weirchert et al. (2009), si valutarono le previsioni delle teorie di regime quando si considera la pendenza come una variabile indipendente. Tre modelli, che incorporano un criterio di stabilità delle sponde, sono stati considerati. Ai fini di valutare la loro performance quando la pendenza è un controllo esterno, due modificazioni a questi modelli sono state proposte. Lo studio utilizza i dati dei fiumi rilevati nonché un database pubblicato composto da 92 tratti fluviali e 36 studi di caso di laboratorio. Alla fine, il modello di Millar (2005) è stato utilizzato per spiegare i cambiamenti recenti nei fiumi Brenta e Piave ed anche per valutare la loro possibile tendenza evolutiva. L’ultima parte della tesi è stata indirizzata allo sviluppo, validazione ed implementazione di un modello bidimensionale basato sui processi, che è stato chiamato LICAN-LEUFU 2D. Questa parte del lavoro si basa sull’ipotesi che “la morfologia del canale è non solo una conseguenza dei processi che aggiscono sul canale ma anche guidata da questi processi; inoltre, due dimensioni spaziali insieme ad un modello “depth-average” permettono di descrivere meglio la morfologia del canale”. La prima parte afferma che i processi sono i responsabili delle forme osservate nel canale, affermazione che costituisce il punto di vista assunto in questo studio per quanto riguarda il dibattito intorno alle teorie di regime. Tuttavia, non deve interpretarsi come un’opposizione alle teorie di “extremal hypothesis”, oppure che non siano utile per prevedere la forma dei canali. Al contrario, come verrà dimostrato nella revisione dello stato dell’arte, le extremalhypotesis esprimono il comportamento del fiume alla scala di tratto, mentre in questo studio, le caratteristiche osservate alla scala di tratto verranno spiegate dai processi che aggiscono ad scale minori. La seconda parte dell’ipotesi significa che un modello bidimensionale dovrebbe prevedere in miglior modo la morfologia di un canale da quanto si ottiene applicando un modello aggregato o unidimensionale, es.., il modello deve essere in grado di prevedere la geometria a scala di tratto (larghezza e profondità) nonchè la morfologia all’interno del tratto (pozze e raschi), che eccedono le capacità dei modelli essistenti. Il modello è stato testato in tre differenti condizioni. Il primo test è stato realizzato sulla base delle misure di canaletta condotte presso l’Università di Hull. Il modello doveva prevedere la risposta di una canaletta di laboratorio, con fondo sabbioso-ghiaioso, che sviluppava una corazza statica in una situazione di apporto nullo di sedimenti. Nel secondo test il modello è stato utilizzato in una simulazione di medio-termine per estimare la forma del Fiume Azul quando vengono fornite come dati di input, le portate, il materiale di fondo ed il apporto de sedimenti. In questo modo, il test costituisce un’applicazione di un modello 2D nel campo delle teorie di regime. L’ultimo test riguarda l’applicazione del modello per lo studio di un caso: il Fiume Brenta. Il modello è stato caricato con una morfologia iniziale dell’alveo corrispondente all’anno 2010, e la granulometria superficiale. Il modello ha simulato il passaggio di tre piene straordinarie che si susseguirono nel periodo 2010-2011. Le previsioni del modello sono state confrontate con il DTM (modello digitale del terreno) che è stato rilevato alla fine del periodo. Inoltre, il modello è stato utilizzato per valutare la possibile tendenza evolutiva del tratto a medio termine.

This thesis is a collection of three essays on the economics of transboundary river management (contained in chapters 2-4) the contents of which is outlined below: Chapter 2 examines the equity-efficiency trade-off on a transboundary river where an upstream and a downstream riparian withdraw irrigation water. Equity is defined as ‘equal sharing of waters’ - a notion consistent with egalitarianism and equality of opportunity. Property rights are undefined, a priori, but riparians can enter an equal quota cooperative agreement (with side payments and restricted trade in water quotas). We find that the equity-efficiency trade-off is relatively insignificant, in prevalence as well as magnitude, and limited to special cases where the upstream riparian has a substantial relative cost advantage and/or water is very scarce. Chapter 3 examines a transboundary river conflict arising when upstream hydropower water releases do not coincide with the seasonal irrigation needs of a downstream riparian. We consider and rank the qualitative impact of a range of infrastructure investments, potentially initiated and co-financed by multilateral development banks (MDBs). Basinwide social efficiency and regional stability can, under certain conditions, be improved through Pareto-improving investments, including enhancement of upstream hydropower efficiency and expansion of downstream reservoir capacity. The findings are used to analyse proposed infrastructure projects in the Syr Darya Basin shared by Kyrgyzstan, Uzbekistan and Kazakhstan. Chapter 4 examines riparian cooperative behaviour on the Syr Darya river. To resolve their conflict of interest, riparian states have resorted to annual cooperative agreements. This arrangement, however, has largely failed due to lack of trust between the parties. Striving for self-sufficiency in irrigation water, Uzbekistan has initiated new reservoir construction. The chapter examines their economic impact. We report a laboratory experiment modelling the Syr Darya river scenario as a multi-round three-player trust game with non-binding contracts. Payoff schemes are estimated using real-life data. While basinwide efficiency maximisation requires regional cooperation, our results demonstrate that cooperation in the laboratory is hard to achieve. Uzbek reservoirs improve the likelihood of cooperation only weakly and their positive economic impact is limited to low-water years.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2002.
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In this thesis, we investigate atmospheric water vapor transport through a distinct synoptic phenomenon, namely, the Tropospheric River (TR), which is a local filamentary structure on a daily map of vertically integrated moisture flux. Firstly, an automated procedure for identifying and tracking these rivers (named TRICKS, i.e., the Tropospheric River Identifying and traCKing Scheme) is described and its performance is evaluated. This procedure enables the maxima of moisture flux (so-called TR cores) to be detected and accurately located. The relationships among the adjacent TR cores are then evaluated to construct the axes of rivers. A river is tracked from birth to termination and its life cycle properties are recorded, thus allowing various statistics of TR distributions and movements to be estimated. All these stages of the scheme are performed without intervention once a number of governing constants have been decided upon. We then apply the scheme to the vertically integrated moisture flux calculated from 43 years of 6-hourly NCEP/NCAR reanalyses and present a climatology of mean TR behavior. On average, there are 4 - 5 rivers per analysis in the Northern Hemisphere and 5 in the Southern Hemisphere. Northern Hemisphere TRs form and intensify near the eastern seaboards of Asia and North America. They move eastward and poleward during their lives before weakening in the two principal graveyards: over the Gulf of Alaska and the region to the southeast of Greenland. In comparison, Southern Hemisphere TRs are more evenly distributed and tend to form in a band extending from the southeast coast of South America into the Atlantic, across the Indian Ocean, and throughout much of middle latitudes of the Pacific sector.
(cont.) The corresponding genesis regions are also found to be adjacent to (or slightly equatorward to) the maximum SST gradients in these regions. It appears that both TR genesis and termination maxima tend to be displaced near the upstream equatorward flanks of cyclogenesis and lysis maxima. We suggest that the TR formation and termination could be a leading predictor for the occurrence and decaying of extratropical cyclones. TR axis length appears to be longer during the warmer season and in the Southern Hemisphere. The distance traveled by TR systems shows a broad distribution and a sizeable fraction (-25%) of systems travel in excess of 3000 km. One unique feature is that although TRs occur very actively over the Indian ocean sector with highly densed tracks, large translational speeds, and intensities, they contribute little to meridional water vapor transport, while the reverse situation can be found in the South Pacific where southward transport is sometimes comparable to those over or off the east coast of South America. The rivers seem to account for a substantial fraction of the total meridional moisture transport in both middle and subtropical regions. Finally, we complete the TR climatology with an analysis of the variability and trends exhibited by many aspects of rivers during the 43-year period. The annual average number of TRs per analysis has undergone an overall increase during the last couple of decades and is more significant in the Southern Hemisphere. The greatest increases occur in the 50⁰-30⁰S and 50⁰-70⁰N belts ...
by Yuanlong Hu.
Ph.D.

This research attempts to fill in some specific gaps in the area of economic valuation of non-market goods and services with respect to development projects, and the integration of those values in the policy decision-making process. The concept and theory of non-market valuation and project appraisal are examined. In a developing country context, the conventional contingent valuation method is extended to include respondents' contribution in terms of time, irrespective of their decision to contribute money. This extension of the conventional contingent valuation method allows the inclusion of economic activities that are non-monetized and transactions in the form of 'barter exchange', which are typical for developing countries such as Bangladesh. The values generated by this new approach are integrated into an extended cost-benefit analysis, which reveals that the cleanup of dying rivers is not only an environmental imperative, but is also socially and economically justifiable. Apart from the theoretical investigation, another important dimension of this research is to contribute to the policy decision-making process with regard to public sector investment in developing countries. The Buriganga River, which passes through Dhaka City, the capital of Bangladesh, has been selected as the case study for this research. Although considered to be the lifeline of the capital, the city part of the Buriganga River has become biologically and hydrologically dead because of the indiscriminate dumping of domestic and industrial wastes, encroachment by unscrupulous people, and negligence on the part of the authority to enforce rules and regulations pertaining to the ecological health of the river. A cleanup programme has been designed for the Buriganga River to restore its water quality and develop new facilities in and around the river. This hypothetical cleanup programme is used: (i) to estimate the non-market benefits of an environmentally healthy waterway; (ii) to measure the total benefits; and (iii) to examine the desirability of public funding for the cleanup programme. An extended contingent valuation (ECV) survey of 400 households was carried out in Dhaka City in 2001. It reveals that not only are a significant proportion of the respondents willing to contribute direct cash for the environmental improvement of the river, they are also willing to contribute their time. When the contribution in terms of time is monetized, it is estimated to represent about 60 percent of the total contribution (the remaining 40 percent being cash payment). The total non-market benefits from the Buriganga River cleanup programme are estimated at Tk 388 million (US$ 6.80 million) in the first year, rising to Tk 1805 million (US$ 31.66 million) by the 10th year of the programme. The public decision making process in Bangladesh does not consider such benefits. Failures to do so lead to gross under-estimation of the potential for, and contribution of, undertaking environmental improvement activities. The total benefits of the cleanup programme are estimated within the framework of total economic value: the non-market benefits are estimated using the ECV survey inputs, and the market benefits are measured using secondary information, market methods and a benefit transfer approach. The cost estimate of the cleanup programme is made using market and secondary information with appropriate adjustments. The extended cost-benefit analysis (ECBA), which integrates the non-market benefits of the cleanup programme, shows that such public funding is worth undertaking. The study also reveals that a significant portion (68 percent) of this investable funding can be generated from the community. The need for a cleanup programme of the Buriganga River is not an isolated case in Bangladesh. Many rivers in that country, and also throughout the developed and developing world are under threat of becoming biologically and hydrologically dead. This study provides a framework for addressing such environmental problems. It demonstrates that the ECV survey is a useful tool in estimating economic values of resources even in extremely poor economies. The modification of the contingent valuation method takes into account the local context, including cultural, economic, social and political settings. The extended cost-benefit analysis, which integrates better resource values could provide important information for the policy decision-making process. This is particularly useful for countries where the democratic system is not fully developed and there is limited experience in integrating the environment into the decision making.

In the paper, after presenting the terraces identification methodology (field research, drilling data, fauna remains, cartographic materials, satellite images, and bibliographic sources), describes rock type structure and morphometric parameters of terraces and rivers beds levels in the area of the biggest hydrographic basin located between the Prut and Nistru rivers – the Raut river basin. They identified and described five Pleistocene terraces and two levels of the upper Pliocene age in the river’s valleys. A detailed rivers terraces levels analysis showed that fault and folded formations found in the sedimentary cover of Moldovan plate, together with hydrologic characteristics and basic level oscillations were part of the fluvial morphogenesis during Neogene and Pleistocene age.

Rivers play a vital role in enhancing the identity of any city. Similarly, Mula, Mutha, and Mula-Mutha rivers are the identity of Pune city. When we look at the rivers of Pune closely, we will find the horrendous scenario. The major issues with the rivers of Pune are river flooding, river pollution, partial dry riverbeds, underutilized riverbanks, slum encroachment, and inaccessibility. These rivers are in a vulnerable state due to rapid urban growth. The unplanned growth of Pune city has degraded the quality of its river. The overall perspective towards the river has changed and the city is showing its back to its rivers. These kinds of scenarios have raised challenges for Pune city which is affecting the lives of its citizens. Therefore, we should investigate these issues closely and come up with the best possible compatible solutions for retaining the identity of the city and enhancing the quality of life. The riverfront development along these rivers can overcome these issues and integrates socio-cultural, economic, and environmental activities which are existing along the rivers of Pune.

Dry weather flow is forms due to the depletion of both groundwater reserves and channel reserves, which still remain in the river network, lakes and swamps after the termination of the supply of surface thaw-rainwater from spring irrigation. Forecasts of the river boundary flow in the summer, autumn and winter period are used in the development of monthly and decadal plans for the operation of large reservoirs, in the planning of navigation, energy production of hydroelectric power plants on rivers, which should ensure reliable, uninterrupted operation of economic facilities, as well as in forecasts of low water in rivers. The object of the research is the rivers of the Southern Bug river basin. The summer and winter dry weather flow on the rivers of the Southern Bug river basin is characterized by stability, low water and considerable duration; autumn rises are observed after torrential rains. Sometimes the dry weather flow is broken by small rain floods. The purpose of this work is to develop a methodology for territorial forecasting of the dry weather flow of rivers in the Southern Bug river basin and to evaluate its effectiveness, a cartographic presentation of the predicted values of the dry weather flow and to determine the probability of their occurrence in a multi-year period. The basis of the forecast of low water flows in the dry weather flow period of rivers in the basin of the Southern Bug River is the solution of the water balance equation in the form of dependencies generalized for a number of the water gauge station. According to the data on water flow (runoff modules) on the date of the forecast release and averages for the decade, regional dependencies were constructed for each month of the season of low water flow of rivers separately. The methodology of territorial short-term forecasts of the average decadal flow of water of the dry weather flow summer, autumn and winter runoff of rivers in the basin of the Southern Bug River is evaluated as satisfactory - the interval of the criteria of quality and efficiency of the methodology is 0.68-0.84, and the short-term forecasts evaluation is quite high - Р % varies from 70% to 94%, with the number of members of the series exceeding 500 points. In the prognostic method of territorial short-term forecasts of the dry weather flow of rivers in the basin of the Southern Bug River, it is proposed to establish the certainty or probability of exceeding (probability of occurrence of) forecast values (P%), which is especially important for rivers that have not been studied in terms of hydrology. In order to determine the reliability of forecast values of average decadal water flows of the summer, autumn and winter dry weather flow, the empirical distribution of the average monthly runoff modules in the specified boundary seasons in river basins in the basin of the Southern Bug River was established. Map-schemes of distribution on the territory of forecast values of average decadal water consumption and their probable values were constructed using the program Surface Mapping System Surfer Version 11.6.1159. The map schemes are built on the date of the release of the forecast make it possible to carry out spatial monitoring of the dry weather flow of rivers and to issue forecasts of water runoff during this period in a specific point of the territory, even for those rivers for which there is no monitoring of the runoff.

Small rivers are important in terms of water quantity and quality as these rivers collect and deliver water to medium and large rivers downstream. Due to low water flow and high connectivity to adjacent land, small rivers are highly vulnerable to changes caused by natural and anthropogenic factors. This paper aims to assess the chemical and ecological quality of two small rivers including the Slocene and Age as related to dominant land use cover in the contributing area of these water bodies. The effects of land-use patterns and concentrations of chemical substances TN, NO3 --N, NH4 +-N, TP and PO4 2--P in river waters will be determined. The highest concentration of total nitrogen (TN) as measured in the Slocene river was 21 mg L-1 in spring, while the lowest concentration of TN was 0.86 mg L-1 in autumn. The highest concentration of total phosphorus (TP) in the Slocene river was 0.14 mg L-1 in late summer, the lowest was 0.03 mg L-1 in late autumn. Similarly, in the Age river, the highest concentration of TN was 4.90 mg L-1 in spring, while TN the lowest concentration of TN was 0.51 mg L-1 in late autumn. The highest concentration of TP in the Age river was 0.3 mg L-1 in summer, while the lowest 0.05 mg L-1 in autumn.

The issues of complex assessment of the state of steppe landscapes based on the analysis of the functioning of catchments of small rivers are considered. As an example, the calculation of the index of optimal functioning of key catchments of small rivers in the Ural River basin is presented. An integral index of the functional state of small river catchments has been developed and tested.

The formation of floods of mixed origin in the cold and warm periods of the year is characteristic of the rivers of Transcarpathia. They are often accompanied by significant and prolonged flooding of territories, sometimes with catastrophic consequences. For the purpose of warning about dangerous hydrological phenomena, an urgent task is hydrological forecasting of maximum levels and water flows during periods of floods on rivers. The object of the research is the Tysa River and its tributaries, which are characterized by the formation of maximum runoff from melting snow and rainfall in the winter-spring period. The Carpathians, which occupy the southwestern part of Ukraine, play a major role in shaping the climate of the territory under consideration, where a mountain climate associated with heavy precipitation is created. It should be noted that heavy precipitation in the Tysa river basin is characterized by a long duration and intensity of precipitation. Such rains are accompanied by the rapid formation of catastrophic river floods, mudslides and floods. The purpose of this work is the analysis of modern mathematical models for forecasting the maximum water levels and discharges of floods and the creation of a methodology for short-term forecasting of the flood flow of Transcarpathian rivers. Mathematical models of rain and snow-rain runoff of mountain rivers were developed as structural components of basin prognostic systems (in the Tysa basin - "Tysa", in the Latorica river basin - "LATORICA", 2011). Such models were created at the Ukrainian Research Hydrometeorological Institute of the State Emergency Service of Ukraine and the National Academy of Sciences of Ukraine (UkrHMI) https://uhmi.org.ua/dep/hydro/ and are implemented in the operational activities of the Transcarpathian Regional Center for Hydrometeorology http://gmc.uzhgorod.ua/vgpro.php. These models are conceptual with concentrated parameters and serve for short-term forecasting of runoff (discharges /levels) during rain and snow-rain floods and long-term forecasting of spring flood characteristics. In foreign practice, a new generation MIKE 11 modeling complex has been developed and is used in the operational practice of European countries. In UkrHMI, the adaptation of the NAM RR MIKE 11 hydrological model to calculation and forecast modeling of both average daily and maximum discharges of the mountain rivers of Transcarpathia (the rivers Tysa, Rika, Borzhava). The quality of NAM module calibration is related to the quality and availability of hydrometeorological data and the impact of anthropogenic activities on river flow. In addition, as part of the adaptation of the MIKE 11 model, predictive hydrological modeling was carried out based on the data of the WRF NMM mesoscale short-term weather forecast model and satisfactory results were obtained. The basis of the development of the method of forecasting the maximum flood water levels by the authors is the method of appropriate levels for the Tysa River, taking into account the data of automatic posts under different conditions of the formation and superimposition of flood waves along the river and its tributaries. The physical basis of the method of forecasting discharges and water levels in river sections is the Saint-Venant equation, which reflects the basic patterns of movement of river waves in a one-dimensional approximation. The essence of the method is to establish an empirical relationship between the appropriate levels (discharges) of water observed in the upper and lower reaches. The prematurity of the forecast is equal to the difference in the timing of the occurrence of such levels (discharges) in the specified creations. Thus, in order to warn about the negative consequences of passing the maximum water levels of floods of mountain rivers of Transcarpathia, which are caused by heavy precipitation or melting snow, it is carried out both when using modern prognostic mathematical models and when using the method of appropriate discharges or water levels.

During the lockdown imposed due to the first wave of the coronavirus disease (COVID-19) pandemic, there were several media reports of citizens flouting the lockdown rules in the United States. Upon closer investigation it was found that the rules were flouted mostly so that people could spend time outdoors in natural environments. This exemplifies the role of the natural environment as a panacea to the mental stress created by pandemics. River ecosystems are perhaps the greatest natural feature of any city. Efficient management of urban rivers, therefore, is strongly correlated to crisis management during pandemics like COVID-19.

River governance is notoriously complex. Climate change will alter how people interact with rivers. Will current river governance structures serve us in the future? Or is it time to reconsider our current rules and regulations?

This report documents the geomorphic assessment component of the Old River, Mississippi River, Atchafalaya River, and Red River System Technical Assessment. The overall objectives of the geomorphic assessment are to utilize all available data to document the historic trends in hydrology, sedimentation, and channel geometry for the rivers in the vicinity of the Old River Control Complex and to summarize the changes observed at locations where repetitive datasets exist and at key reaches that are determined during the study. The geomorphic assessment tasks include data compilation, geometric data analysis, gage and discharge analysis, dredge record analysis, sediment data analysis, development of an events timeline, and integration of results. Geomorphic reaches were developed, and the morphological trends during different time periods were identified. The geomorphic assessment highlighted the importance of considering spatial and temporal variability when assessing morphological trends.

The Old River Control Complex (ORCC) consists of the Low Sill, Auxiliary, and Overbank structures as features of the Old River Control Structure (ORCS) and the privately owned hydro-electric power plant. Operations of the ORCC manage the hydrologic connectivity between the Mississippi River and the Atchafalaya River/Red River systems. The morphology of the Old, the Mississippi, the Atchafalaya, and the Red Rivers (OMAR) has been influenced by the flow distribution at the ORCC, as well as the accompanying bed sediments. A geomorphic assessment of the OMAR is underway to understand the morphological changes associated with operation of the ORCC. Supporting the geomorphic assessment, a channel geometry analysis herein documents observed adjustments of the affected river channels. Historical hydrographic survey data were used in the Geographic Information System to create river channel geometric models, which inform the analysis. Geometric parameters for cross sections and volume polygons were computed for each survey and evaluated for morphological trends which may be ascribed to the influence of the ORCC. Additionally, the geometric parameters for the Atchafalaya River were used to extend the geometry analyses from the 1951 Mississippi River Commission report on the Atchafalaya River, which was the primary catalyst for the initial development of the ORCS.

This report is part of the (OMAR) Assessment (defined herein), intended to provide a comprehensive assessment of the interconnected Mississippi, Red, and Atchafalaya Rivers, and the potential results of various changes. This report details the multi-dimensional modeling efforts undertaken to characterize the hydrodynamic and morphodynamic response of the Mississippi River to both the existing configuration and to various proposed operational, dredging, and structural scenarios.

Upstream of the confluence of the Red River, Atchafalaya River, and ORCC Outflow Channel are vast low-lying flat areas on both sides of the Lower Red River. During times of high water on the Lower Red—whether from upstream water in the Red or from the ORCC Outflow Channel—enormous amounts of water flow over the natural riverbanks and flood this land. The loss of this water from the river into storage affects the operation of the ORCC, which in turn affects the stages and flows down the Atchafalaya and Mississippi Rivers. An improved understanding of this area and how water is stored during flood events is required to inform ORCC water management operations. Hydraulic analyses provide a basis to assess the changes in water levels, current directions and velocities, and flow rates for the assessment area. The hydraulic model HEC-RAS is used to expand on existing models of the area and to help overcome gaps in data. Understanding the processes of how water leaves the Red River channel, the volume and timing of the water moving into storage, and when the storage area begins to drain, will greatly inform the water managers and operators of the ORCC.

The Red River, Atchafalaya River, and the Old River Control Complex (ORCC) Outflow Channel Adaptive Hydraulics two-dimensional depth averaged sediment model (AdH-2D-SED) was used to evaluate the short-term and system-wide sedimentation effects of modifying the operation schedule at ORCC. The changes evaluated were increasing and decreasing the percentage of flow that is diverted to the Atchafalaya River from the Mississippi River at the ORCC and modifying the distributions through four ORCC structures. Sedimentation effects for several operation scenarios were compared to a Base condition for each water year that represented the existing operation protocols. Four dredging scenarios were developed and analyzed. Additionally, two structure options were developed and analyzed. The scenario analyses presented in this report are intended to identify large trends and to make gross assessments of the potential impacts of various proposed operational changes to the ORCC.