Littérature scientifique sur le sujet « Hydrological failure »

Early on the morning ofMarch 27, 2009, the Situ Gintung dam, located near Jakarta, Indonesia, and with an catchment area of 3.1 km2, failed and flooded the area below it. This disaster has awakened most of the Indonesian people, especially those who are concerned about hydraulic structures, natural disasters and sustainable water resources management. During the disaster, about 100 people died and a number of people went missing. There are hundreds of dams like the Situ Gintung dam and other big dams have been built in Indonesia. Most of these dams pose a high potential hazard to life and property if a failure or levee breach occurs. Dam failures may occur at different locations such as spillway, embankments and foundations. The failure may occur as a result of a number of problems such as overtopping, surface erosion, and piping. Dam failures due to spillway problems may occur, for instance, as a result of inadequate spillway capacity (overtopping) or spillway loss by erosion (surface erosion). In this study, the Situ Gintung dam failure has been analyzed based on hydrology analysis. Results show that heavy monsoon rainfall was not the main cause of the situ Gintung dam failure. The daily rainfall on March 26, 2009, was 113 mm that equal to a 10 year return period. Reservoir routing shows that there was no overtopping during March 27, 2009, flood, the maximum water depth on the spillway is 0.63 m. Assuming that maintenance was done well, the spillway was still safe under a 100 year return period with the maximum water level is +98.95 m. It means that the embankment was still safe with 1.05 m freeboard. Due to high water flow velocity, however, surface erosion may occur at the end of a chute spillway that consists of silt, clay and sand. Continuous scoring/erosion happened throughout the spill over the spillway, which started at around 06:00 pm and lasted until 03.00 am, resulting in a big pond at the chute spillways and surrounding areas. This phenomenon adversely affected the instability of the spillway structure. As a result, the spillway failure occurring resulted high flow discharge that reached more than 425 m3/s.

Abstract. Population growth will in many regions increase the pressure on water resources and likely increase the number of people affected by water scarcity. In parallel, global warming causes hydrological changes which will affect freshwater supply for human use in many regions. This study estimates the exposure of future population to severe hydrological changes relevant from a freshwater resource perspective at different levels of global mean temperature rise above pre-industrial level (ΔTglob). The analysis is complemented by an assessment of water scarcity that would occur without additional climate change due to population change alone; this is done to identify the population groups that are faced with particularly high adaptation challenges. The results are analysed in the context of success and failure of implementing the Paris Agreement to evaluate how climate mitigation can reduce the future number of people exposed to severe hydrological change. The results show that without climate mitigation efforts, in the year 2100 about 4.9 billion people in the SSP2 population scenario would more likely than not be exposed to severe hydrological change, and about 2.1 billion of them would be faced with particularly high adaptation challenges due to already prevailing water scarcity. Limiting warming to 2 ∘C by a successful implementation of the Paris Agreement would strongly reduce these numbers to 615 million and 290 million, respectively. At the regional scale, substantial water-related risks remain at 2 ∘C, with more than 12 % of the population exposed to severe hydrological change and high adaptation challenges in Latin America and the Middle East and north Africa region. Constraining ΔTglob to 1.5 ∘C would limit this share to about 5 % in these regions.

The hydrological environment must be understood before water flow can be adequately controlled to prevent slope failure without impacting unduly on the hydrological mountain slope environment. We conducted field studies to determine current sites and measurement of ground temperature 1 meter deep to clarify groundwater flow passageways on the slope behind the cultural heritage temple Kiyomizudera in Kyoto. Results showed anomalous temperature 1 meter deep bands on the slope and several springs that are extensions of these bands. Several of these bands coincide with terrain deformations such as gullies and slope failure scars indicating the probability of relationships between groundwater flow and topological deformation.

Understanding the hydrological and physical responses of shallow slopes subject to rainfall events is vital for the efficiency of a warning system setup. In this research, a series of experiments were undertaken to evaluate the hydrological responses of shallow slopes of varying steepness and when subjected to varying intensities, periods, and inter-storm periods of rainfall. An analysis of infinite slopes was also undertaken to develop a fundamental understanding of rainfall-induced shallow slope failure characteristics. The hydrological and physical responses were characterized in the infiltration and saturation phases. During the infiltration phase, the maximum magnitude of water content was found behind the wetting front, termed as the water content behind the wetting front (θwb). For a certain soil type, the magnitude of θwb was found to be dependent on the magnitude of rainfall intensity, regardless of the slope gradient and initial water content. Based on the relative depth of the failure plane, the failure can be categorized by three prime modes: (i) along the impervious layer mode, (ii) shallow depth mode, and (iii) transitional mode. These modes can be characterized by the magnitude of a stability index termed as [Formula: see text] ratio. An infiltration index, termed as i/ks ratio, was found to play a role in the depth of the failure plane only for the transitional mode.

Extensive hydrological analysis is carried out to estimate floods for the Batu Dam, a hydropower dam located in the urban area upstream of Kuala Lumpur, Malaysia. The study demonstrates the operational state and reliability of the dam structure based on hydrologic assessment of the dam. The surrounding area is affected by heavy rainfall and climate change every year, which increases the probability of flooding and threatens a dense population downstream of the dam. This study evaluates the adequacy of dam spillways by considering the latest Probable Maximum Precipitation (PMP) and Probable Maximum Flood (PMF) values of the concerned dams. In this study, the PMP estimations are applied using comparison of both statistical method by Hershfield and National Hydraulic Research Institute of Malaysia (NAHRIM) Envelope Curve as input for PMF establishments. Since the PMF is derived from the PMP values, the highest design flood standard can be applied to any dam, ensuring inflow into the reservoirs and limiting the risk of dam structural failure. Hydrologic modeling using HEC-HMS provides PMF values for the Batu dam. Based on the results, Batu Dam is found to have 200.6 m3/s spillway discharge capacities. Under PMF conditions, the Batu dam will not face overtopping since the peak outflow of the reservoir level is still below the crest level of the dam.

Simulation of dam breach scenarios can help in the preparation of emergency action plans for real dam breaks or flash flooding events. The purpose of this study was to identify flood-prone areas in the Al Wala Valley in the governorate of Madaba in Jordan through analysis of the Al Wala Dam. Modelling of dam breaches was conducted under two scenarios: a Clear Day scenario and a Probable Maximum Flood (PMF) scenario. The former scenario does not address the various dam failure modes; rather, it addresses the formation and development of a breach as a result of structural failures like the sliding of dam blocks in the case of a concrete dam or piping failures in the case of embankment dams. The PMF scenarios, however, simulate unsteady flow in pipes and overtopping failure via consideration of runoff hydrography. In the PMF scenario, flood-prone areas can be identified by in-depth analysis of data from previous extreme rainfall events. The related hydrologic and hydraulic data can then be modelled using intensity-duration-frequency curves applied to an hour-by-hour simulation to discover the areas most at risk of flooding in the future. In the present study, data were collected from inlet of flow to Al Wala Valley on 10 January 2013. The collected data, which included rainfall and discharge data, were fed to the HEC-HMS software in order to calibrate the hydrological parameters of the watershed of the Al Wala Dam. Additionally, the HEC-RAS tool was employed to determine the breach outflow hydrography and hydraulic conditions across various critical downstream locations, which were determined by use of dynamic flood wave-routing models. The simulations revealed that, in the case of the Clear Day scenario, downstream inundation would cover an area of 5.262 km2 in the event of a pipe failure. However, in the event of a six-hour storm, a twelve-hour storm, and a twenty-four-hour storm, the flooded area would rise to 6837 km2, 8518 km2, and 9390 km2, respectively. In the event of an overtopping failure, 13,171 km2 would be inundated, according to the Clear Day scenario. On the other hand, in the event of a six-hour storm, a twelve-hour storm, and a twenty four-hour storm, the flooded area would rise to 13,302 km2, 14,249 km2, and 14,594 km2, respectively.

Abstract. The risk of failure of transportation embankments due to seepage induced by temporary and occasional impoundments taking place on the upstream side as a consequence of exceptional rainfalls is frequently underestimated. These failure events result from a combination of three main factors, i.e. the flooding event, the hydraulic weakness and the geotechnical weakness of the embankment. Based on the case study of a railway embankment in Southern Italy that collapsed in 2005 due to an upstream impoundment that occurred after few hours of a very intense rainfall, the paper describes a methodological approach aimed at assessing hazard of failure of transportation embankments induced by flooding and seepage. In particular, according to hydrological, hydraulic and geotechnical studies performed to define the factors affecting the process of the embankment failure, three subsequent activities are proposed: the historical analysis of flood damages at the watershed scale; and the assessment of the upstream peak impoundment based on hydrological analysis and the embankment stability analysis, these latter to be carried out at the site specific scale. The approach here proposed is planned to be further validated and improved by means of the application to other case studies, characterised by different contexts and embankment structures.

Three recent shallow landslides over permafrost are described. Slides occur in low- to medium-plasticity clays containing some bands of silts and fine sands. Slope failure results from rapid thaw at the base of the active layer of soil that is ice-rich due to antecedent two-sided freezing. Displaced slide blocks retain their integrity because of hardening of the active layer by cryodesiccation and summer evaporation. Blocks move over a soft basal shear zone a few millimetres to several centimetres thick. Compression in the toe zone of slides is low at sites where runout is possible, but in other locations causes emergent shears and complex folding. Failure histories are varied and range from simple unitary slides to complex sequential failures in which active-layer segments are mobilized progressively higher up the slope. This study demonstrates the importance of active-layer thermal and hydrological regimes, in addition to material properties, in determining the mode of slope failure.

The main subject of the present thesis is the triggering of debris flows, which has been studied from a geomorphological and from a hydrological point of view. The thesis is a compilation of three papers, each one focused on a specific part of the triggering mechanism. In fact, debris flows are dangerous events, typical of mountain territories all over the world and they necessitate the concurrence of many variables to be triggered. In the last decades, different studies stated that the main variables involved in the initiation of a debris flow are: terrain slope, water input and sediment availability. If these factors exceed some specific critical thresholds, the probability of a debris flow triggering can be very high. However, the fact that so many variables are involved makes these events difficult to forecast. In the present study, we analysed different aspects related to the triggering probability. For this reason, the thesis is composed of three different papers: (1) Chapter 2, titled “On the criteria to create a susceptibility map to debris flow at a regional scale”; (2) Chapter 3, titled “Correlation between the rainfall, sediment recharge and triggering of torrential flows in the Rebaixader catchment (Pyrenees, Spain); (3) Chapter 4, titled “Rainfall durations and corresponding dominant mechanism for the initiation of debris flows in three basins characterized by different geomorphological settings”. In Chapter 2, we analysed the geomorphological variables of the catchments that have the most important role in the triggering of debris flows. We used a model named Flow-R that works at a regional scale (allowing to analyse an entire valley) to study the potential triggering areas, neglecting the hydrological part of the mechanism. In fact, starting from a real case study (event of 4th August 2012), we used the collected data regarding the triggering and deposition areas to model the debris flow event. We analysed the morphological parameters that had better discriminate the potential triggering areas from the zones in which the erosion and slope failure are highly improbable. In Chapter 3, we studied the two triggering variables related to water input and sediment recharge. In this case, we focused on: (1) rainfall, investigating its influence on the triggering of debris flows and on the accumulation and mobilization of sediments; (2) sediment availability, considering the registered debris flow volumes as the previously available sediment quantity inside the triggering area, in the period before the triggering of the event. The analysed catchment is in the Spanish Pyrenees and it is a good case study because since summer 2009 it has been equipped with a monitoring station (rain gauges, piezometers, video cameras, geo-phones). Therefore, the rainfall datasets registered with a time interval of 5 minutes inside the catchment are relatively long and allows to study potential correlations between the water input and the sediment mobilization. We searched if there are any correlations between the volume of the triggered event and the total precipitation of the recharge period (the period between the considered debris flow and the previous one). We then analysed the correlations between the maximum rainfall intensities of the triggering rainfall events and the volume of the debris flows. Finally, we used a parameter called “rainfall erosivity” that, calculated for each rainfall event, considers at the same time the total precipitation, the maximum intensity and the kinetic energy of the rain. This parameter has been calculated using two different time scales: (1) for the single triggering rainfall event; (2) as the sum of all the rainfall events happened during every recharge period. The results are interesting because it is clear that rainfall scarcely influences the quantity of the mobilized sediment, evidencing that there are other important variables involved in this mechanism. Whereas, the triggering or non-triggering of a debris flow is strongly dependent on the rainfall erosivity of the triggering rainfall event. After these two analyses, made at the regional scale and at the basin scale, in Chapter 4 we went more in the detail, focusing on the headwater basins (the upper parts of debris flow catchments). We analysed three study areas: (1) the headwater basin of Rio Rudan, located in the south side of Mount Antelao (Italian Dolomites); (2) the headwater basin of Rio Chiesa, located in the south side of Col di Lana (that is also located inside the dolomitic region, but it is characterized by a different geology, mainly composed of volcanic and sedimentary rocks); (3) the headwater basin of Rio Rebaixader, located in the Spanish Pyrenees (mainly composed of metamorphic rocks). In each headwater basin, we extracted three control cross sections along the channel network. For every cross section we calculated the critical triggering discharge for the debris flow initiation using the formulas of Gregoretti and Dalla Fontana (2008) and of Whittaker and Jaggi (1986). Then, we made some hydrological simulations using the software FLO-2D, using as water input different hyetographs created using the Intensity-Duration equations of Gregoretti and Dalla Fontana (2007) and of Cannon and Ellen (1985). These simulations allowed us to verify which is the minimum rainfall duration (related to the corresponding rainfall intensity) needed to reach the critical discharge in the control cross sections. To test also the possible shallow slope failure triggering mechanism, we also made a slope stability analysis in the three initiation areas, using the geotechnical parameters derived from the analysis of terrain samples collected inside the headwater basins. These two different analysis gave an overall view on the mechanism of mobilization of sediments in the analysed areas. The results show that the critical discharges in the three basins are comparable, whereas the slope stability analysis evidences some differences between the basins. In fact, Rio Rudan resulted generally more stable than the two other basins, even with high saturation conditions of the terrain. This can mean that in this basin the principal triggering mechanism is the “channel-bed failure”, whereas in the two other basins mechanisms of “shallow slope failure” are also probable.
La seguente tesi è stata sviluppata in forma compilativa, come raccolta di articoli. Il filo conduttore di tutto il manoscritto è l’analisi del fenomeno di innesco di colate detritiche. Questo tipo di eventi, tipico di zone montane di tutto il mondo, necessita della concomitanza di particolari fattori per poter accadere. Negli ultimi decenni, differenti studi a riguardo, hanno dimostrato che tra le principali variabili in gioco nel determinare l’innesco di una colata, ci sono: la pendenza del terreno, una sufficiente quantità d’acqua e una certa disponibilità di sedimento nell’area sorgente che possa venire mobilizzata. Questi fattori, quando concomitanti sopra ad una certa soglia limite, determinano una elevata probabilità di innesco di un fenomeno di colata detritica. Il fatto però che ci siano in gioco molte differenti variabili, rende questi meccanismi molto difficili da comprendere e predire con estrema esattezza. In questo studio, si è cercato di analizzare tutti gli aspetti legati alla probabilità di innesco per dare un quadro complessivo del fenomeno, prendendo in considerazione differenti variabili in differenti aree di studio. Per questo motivo la tesi è strutturata in tre parti distinte: ad un primo capitolo introduttivo in cui viene presentato il fenomeno di colata detritica nella sua interezza, segue il Capitolo 2, intitolato “On the criteria to create a susceptibility map to debris flow at a regional scale”. In questa parte della tesi, vengono analizzate le variabili geomorfologiche del terreno che incidono maggiormente nel possibile innesco di una colata detritica. Utilizzando un modello chiamato Flow-R che lavora a scala regionale (permettendo di analizzare un’intera vallata e non solamente singoli bacini), si è trascurata la parte idrologica del fenomeno concentrandosi sulla morfologia del terreno. Partendo infatti dai dati reali (dati di pioggia, volumi di colate, mappatura delle aree di innesco e delle aree di deposito) misurati durante e successivamente l’evento del 4 agosto 2012 che ha interessato l’intera Val di Vizze (Provincia di Bolzano) si è cercato di ricostruire nel modo più verosimile l’innesco e la propagazione di colate nel territorio analizzato, cercando di trovare i parametri morfologici che permettessero di discriminare accuratamente le possibili aree sorgenti dalle zone in cui invece l’erosione e l’innesco sono altamente improbabili. Proseguendo con il Capitolo 3 della tesi, denominato “Correlation between the rainfall, sediment recharge and triggering of torrential flows in the Rebaixader catchment (Pyrenees, Spain)” si è invece passati ad analizzare le due variabili pioggia e quantità di sedimento, legate all’innesco di colata detritica. In questo caso, a differenza della precedente analisi, ci si è concentrati: (1) sulla pioggia, analizzando se questa influisca non solo nel determinare lo switch innesco si/innesco no, ma provochi degli effetti anche sull’accumulo e/o mobilizzazione dei sedimenti nelle aree di innesco; (2) sulla quantità di sedimento disponibile per un eventuale innesco di colata, considerando i volumi detritici registrati come il sedimento disponibile, nell’area di innesco, durante il periodo pre-colata. Il bacino analizzato in questa seconda parte della tesi, si trova nei Pirenei spagnoli ed è un ottimo caso studio in quanto fin dall’estate 2009 è stato equipaggiato con una stazione di monitoraggio che comprende pluviometri, geofoni, piezometri e videocamere. La serie storica dei dati di pioggia, che viene registrata con un intervallo temporale di 5 minuti, è quindi relativamente ampia. Inoltre, essendo questo un bacino caratterizzato da un’elevata frequenza di fenomeni di colata detritica e di correnti iperconcentrate, si è avuta a disposizione una serie di una ventina di eventi (con relativo volume di detriti) registrati sempre a partire dall’estate 2009. Una serie di dati di questo tipo, permette quindi di effettuare analisi molto più approfondite rispetto a quelle che si possono fare in singoli bacini non costantemente monitorati in cui ci si limita a prendere in considerazione le giornate caratterizzate da eventi di colata. Si è quindi studiato se ci fosse correlazione tra il volume dell’evento innescato e la quantità di pioggia caduta nel periodo trascorso tra l’evento di colata stesso e il precedente (questo viene denominato in letteratura “periodo di ricarica”). Si sono successivamente verificate le eventuali correlazioni tra l’intensità massima degli eventi di pioggia del periodo di ricarica e il volume del successivo evento innescato. Per fare uno studio più complesso si è deciso di utilizzare una variabile denominata “rainfall erosivity”, questo parametro calcolato per ogni evento di pioggia registrato, mette insieme la quantità totale di precipitazione misurata con l’energia cinetica della pioggia stessa, calcolata utilizzando la massima intensità media nella mezz’ora. Con questo parametro si è differenziato tra la pioggia totale caduta durante il periodo di ricarica e la pioggia del singolo evento innescante. I risultati ottenuti sono molto interessanti, infatti risulta chiaro come la pioggia abbia un’influenza relativamente scarsa sull’accumulo di sedimenti e sulle quantità mobilizzate, dimostrando come queste quantità siano influenzate da altre variabili in gioco, mentre l’innesco o il non innesco di una colata è fortemente dipendente dall’energia dell’evento di pioggia che si verifica sul bacino. Dopo aver svolto una prima analisi a scala regionale e una seconda a scala di singolo bacino, nel Capitolo 4 si è entrati ancora più nel dettaglio, prendendo in considerazione solamente il sottobacino di testata. In questo capitolo, intitolato “Rainfall durations and corresponding dominant mechanism for the initiation of debris flows in three basins characterized by different geomorphological settings”, sono state analizzate tre differenti aree studio: (1) il sottobacino del Rio Rudan, che si trova nel versante meridionale del Monte Antelao, in pieno territorio dolomitico; (2) il sottobacino del Rio Chiesa, posto sul versante meridionale del Col di Lana, caratterizzato da una geologia differente rispetto al primo, composta da una mescolanza di rocce vulcaniche e sedimentarie; (3) il sottobacino del Rio Rebaixader, che si trova nei Pirenei spagnoli ed è composto principalmente da rocce metamorfiche. In ognuno dei tre sottobacini, sono state estratte tre sezioni di controllo, lungo la rete idrografica, e per ognuna di esse sono state calcolate le relative portate critiche di innesco di colata detritica utilizzando le due formule di Gregoretti e Dalla Fontana (2008) e Whittaker e Jaggi (1986). Successivamente in ciascuno dei sottobacini, utilizzando il software di modellazione FLO-2D, sono state effettuate diverse modellazioni idrologiche utilizzando come input di pioggia, differenti pluviogrammi creati utilizzando le equazioni di Intensità-Durata sviluppate da Gregoretti e Dalla Fontana (2007) e da Cannon e Ellen (1985). Queste indagini hanno permesso di verificare quale sia la durata minima di pioggia (legata alla corrispondente Intensità soglia) necessaria per raggiungere la portata critica di innesco nelle sezioni di controllo analizzate. Per completare lo studio sul meccanismo d’innesco nei tre sottobacini analizzati, è stata fatta anche un’analisi di stabilità di versante, utilizzando i parametri geotecnici derivanti da campioni di suolo prelevati nelle aree di innesco. Queste due analisi danno insieme una visione complessiva del modo in cui le colate detritiche si sviluppino nelle aree analizzate. I risultati mostrano infatti come, in tutti e tre i sottobacini, le portate critiche di innesco siano comparabili come grandezza, mentre le analisi si stabilità di versante evidenziano come il bacino del Rio Rudan sia mediamente più stabile rispetto alle altre due aree, anche in condizioni di elevata saturazione del suolo. Questo fa pensare che in questo bacino il meccanismo di innesco più probabile sia il cosiddetto “channel bed failure”, mentre negli altri due bacini ci sono sicuramente anche fenomeni di “shallow slope failure” che avvengono nelle aree dissestate di versante portando grandi quantità di detriti all’interno del reticolo idrologico.

Extreme rainfall events associated with global warming are likely to produce an increasing number of flooding scenarios. A large magnitude of hydrologic events can often result in submerged orifice flow (also called pressure flow) or embankment and bridge overtopping flow, in which the foundation of a bridge is subjected to severe scour at the sediment bed. This phenomenon can cause bridge failure during large floods. However, current laboratory studies have focused on only cases of free-surface flow conditions, and they do not take bridge submergence into account. In this study, abutment scour experiments were carried out in a compound channel to investigate the characteristics of abutment scour in free-surface flow, submerged orifice flow, and overtopping flow cases. Detailed bed contours and three components of velocities and turbulent intensities were measured by acoustic Doppler velocimeters. The results show that the contracted flow around an abutment because of lateral and/or vertical contraction and local turbulent structures at the downstream region of the bridge are the main features of the flow responsible for the maximum scour depth around an abutment. The effects of local turbulent structures on abutment scour are discussed in terms of turbulent kinetic energy (TKE) profiles measured in a wide range of flow contraction ratios. The experimental results showed that maximum abutment scour can be predicted by a suggested single relationship even in different flow types (i.e., free, submerged orifice, and overtopping flow) if the turbulent kinetic energy and discharge under the bridge can be accurately measured.

碩士
國立高雄大學
土木與環境工程學系碩士班
101
Taiwan is an island with abundant of rainfall. The torrential rainfall accompanied with typhoons frequently causes the rise of groundwater level, the increase of slope soil moisture and the pore water pressure so as to degrade the slope stability. Moreover, Taiwan is located at the compressing zone of the Eurasia plate and Philippine plate, with abundant of mountainous topography and poor geological conditions. Therefore, slopeland disasters often occur in Taiwan and result in the loss of lives and economic damage. Based on the aforementioned reasons, research to integrate the effects of hydrological, topographic, and geological factors on slope stability is very important. Different from the traditional limited stress scale studies, on the basis of the achievements of previous modeling tests, this study is going to utilize the self-developed hydrological environment testing box for slope model tests on the geotechnical centrifuge. The test results will be analyzed to research the influence of groundwater seepage and rainfall infiltration to slope failures, so as to investigate the relationship between slope instability and hydrological effects.

The Flood Directive 60/2007/EC requires the European countries to verify the effectiveness of existing flood defence infrastructure to mitigate flood risks. The current practice establishes that the river flood control structures must respect a basic requirement, usually consisting of a certain safe freeboard under a design peak flow rate corresponding to a certain probability of exceedance. This requirement has some critical issues. It is based on a univariate frequency analysis of only flood peak, and therefore it assumes a perfect correspondence between the probability of occurrence of the hydrological variable and the failure of the flood-control structure. The thesis aims to define a methodology to overcome these issues implementing a bivariate hydrological risk analysis for river-related flood risk. The methodology is mainly focused on the overtopping failure for river levees. River levees are the most common river flood-control structure. They are raised, predominantly earth, structures (also called dykes, digues or embankments). The overtopping failure of a river levee caused several flood disasters such as Elbe flood (2002), New Orleans flood (2005), Emilia Romagna Flood (2017) or Arkansan flood (2019). The proposed procedure is carried out through two steps: (i) the evaluation of hydrological failure related to the overtopping risk for a levee; (ii) the estimation of the probability of occurrence of the hydrological failure introducing the concept of the Bivariate Failure Return Period. The hydrological failure is determined considering the mutual interaction between a bivariate hydrological load of peak discharge (Q) and the volume of the hydrograph (V), the river conveyance, and the levee resistance with respect to overtopping. The bivariate hydrological load considers an approximation of the real bivariate distribution of Q and V, functional to determine the hydrological failure. The shape of the hydrographs is classified concerning the overtopping introducing the Overtopping Hydrograph Shape Index (OHSI). The hydrological failure condition is represented by a curve in Q-V space containing all the hydrographs causing the initiation of the damage. This curve demonstrates that not only the peak flow but also the volume of the hydrograph are essential variables to characterise the overtopping failure. The risk of overtopping failure is expressed by the probability of occurrence of the hydrological failure within a new interpretation of the return period. Because of the hydrological failure curve is a function in Q-V space, the return period is estimated in the bivariate framework. Several definitions of the bivariate return period are available, each of which gives a different interpretation of it. This critical issue is overcome introducing the Bivariate Failure Return Period. The Bivariate Failure Return Period assesses the probability of the failure curve of the hydraulic structure generating possible scenarios through a Monte Carlo simulation. Two case studies are presented to demonstrate the applicability of the methodology and the advantages of using it respect to the current practice. In the thesis, the methodology is also applied to the problem of flood damage estimation demonstrating the flexibility and the validity of the proposed procedure. In this case, the hydrological failure consists in equal-euro curve in Q-V space, which includes all the hydrographs causing the same euro flood damages in a site. The procedure proposed needs Q-V data at the target site where the risk is to be assessed but most of the sites are ungauged. This issue is overcome by testing the bivariate regional frequency analysis. It is applied to the case study of the entire Tuscany Region (Italy). By the bivariate regional analysis, the Q-V series can be estimated at ungauged sites, and the uncertainty is reduced at gauged sites.

abstract: This research examines lateral separation zones and sand bar slope stability using two methods: a parallelized turbulence resolving model and full-scale laboratory experiments. Lateral flow separation occurs in rivers where banks exhibit strong curvature, for instance canyon rivers, sharp meanders and river confluences. In the Colorado River, downstream Glen Canyon Dam, lateral separation zones are the principal storage of sandbars. Maximum ramp rates have been imposed to Glen Canyon Dam operation to minimize mass loss of sandbars. Assessment of the effect of restricting maximum ramp rates in bar stability is conducted using multiple laboratory experiments. Results reveal that steep sandbar faces would rapidly erode by mass failure and seepage erosion to stable slopes, regardless of dam discharge ramp rates. Thus, continued erosion of sand bars depends primarily of turbulent flow and waves. A parallelized, three-dimensional, turbulence resolving model is developed to study flow structures in two lateral separation zones located along the Colorado River in Grand Canyon. The model employs a Detached Eddy Simulation (DES) technique where variables larger than the grid scale are fully resolved, while Sub-Grid-Scale (SGS) variables are modeled. The DES-3D model is validated using ADCP flow measurements and skill metric scores show predictive capabilities of simulated flow. The model reproduces the patterns and magnitudes of flow velocity in lateral recirculation zones, including size and position of primary and secondary eddy cells and return current. Turbulence structures with a predominately vertical axis of vorticity are observed in the shear layer, becoming three-dimensional without preferred orientation downstream. The DES-3D model is coupled with a sediment advection-diffusion formulation, wherein advection is provided by the DES velocity field minus particles settling velocity, and diffusion is provided by the SGS. Results show a lateral recirculation zone having a continuous export and import of sediment from and to the main channel following a pattern of high frequency pulsations of positive deposition fluxes. These high frequency pulsations play an important role to prevent an oversupply of sediment within the lateral separation zones. Improved predictive capabilities are achieved with this model when compared with previous two- and three-dimensional quasi steady and steady models.
Dissertation/Thesis
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Appendix F Video 4.2
Doctoral Dissertation Geography 2015

Humans have understood the importance of climate to human health since ancient times. In some cases, the connections appear to be obvious: a flood can cause drownings, a drought can lead to crop failure and hunger, and temperature extremes pose a risk of exposure. In other cases, the connections are veiled by complex or unobserved processes, such that the influence of climate on a disease epidemic or a conflict can be difficult to diagnose. In reality, however, all climate impacts on health are mediated by some combination of natural and human dynamics that cause individuals or populations to be vulnerable to the effects of a variable or changing climate.Understanding and managing negative health impacts of climate is a global challenge. The challenge is greater in regions with high poverty and weak institutions, however, and Africa is a continent where the health burden of climate is particularly acute. Observed climate variability in the modern era has been associated with widespread food insecurity, significant epidemics of infectious disease, and loss of life and livelihoods to climate extremes. Anthropogenic climate change is a further stress that has the potential to increase malnutrition, alter the distribution of diseases, and bring more frequent hydrological and temperature extremes to many regions across the continent.Skillful early warning systems and informed climate change adaptation strategies have the potential to enhance resilience to short-term climate variability and to buffer against negative impacts of climate change. But effective warnings and projections require both scientific and institutional capacity to address complex processes that are mediated by physical, ecological, and societal systems. Here the state of understanding climate impacts on health in Africa is summarized through a selective review that focuses on food security, infectious disease, and extreme events. The potential to apply scientific understanding to early warning and climate change projection is also considered.

This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Climate Science. Please check back later for the full article.The concept of statistical downscaling or empirical-statistical downscaling became a distinct and important scientific approach in climate science in recent decades, when the climate change issue and assessment of climate change impact on various social and natural systems have become international challenges. Global climate models are the best tools for estimating future climate conditions. Even if improvements can be made in state-of-the art global climate models, in terms of spatial resolution and their performance in simulation of climate characteristics, they are still skillful only in reproducing large-scale feature of climate variability, such as global mean temperature or various circulation patterns (e.g., the North Atlantic Oscillation). However, these models are not able to provide reliable information on local climate characteristics (mean temperature, total precipitation), especially on extreme weather and climate events. The main reason for this failure is the influence of local geographical features on the local climate, as well as other factors related to surrounding large-scale conditions, the influence of which cannot be correctly taken into consideration by the current dynamical global models.Impact models, such as hydrological and crop models, need high resolution information on various climate parameters on the scale of a river basin or a farm, scales that are not available from the usual global climate models. Downscaling techniques produce regional climate information on finer scale, from global climate change scenarios, based on the assumption that there is a systematic link between the large-scale and local climate. Two types of downscaling approaches are known: a) dynamical downscaling is based on regional climate models nested in a global climate model; and b) statistical downscaling is based on developing statistical relationships between large-scale atmospheric variables (predictors), available from global climate models, and observed local-scale variables of interest (predictands).Various types of empirical-statistical downscaling approaches can be placed approximately in linear and nonlinear groupings. The empirical-statistical downscaling techniques focus more on details related to the nonlinear models—their validation, strengths, and weaknesses—in comparison to linear models or the mixed models combining the linear and nonlinear approaches. Stochastic models can be applied to daily and sub-daily precipitation in Romania, with a comparison to dynamical downscaling. Conditional stochastic models are generally specific for daily or sub-daily precipitation as predictand.A complex validation of the nonlinear statistical downscaling models, selection of the large-scale predictors, model ability to reproduce historical trends, extreme events, and the uncertainty related to future downscaled changes are important issues. A better estimation of the uncertainty related to downscaled climate change projections can be achieved by using ensembles of more global climate models as drivers, including their ability to simulate the input in downscaling models. Comparison between future statistical downscaled climate signals and those derived from dynamical downscaling driven by the same global model, including a complex validation of the regional climate models, gives a measure of the reliability of downscaled regional climate changes.

Since the Nara Hydropower Station was put into operation, it has far exceeded the designed service life of 25 years. The generator insulation is seriously aging, the water leakage of the turbine is large, the working efficiency of the unit is low, the operation failure occurs frequently, and the hidden safety problems are prominent. At present, the upstream cascade power station and the leading reservoir have been constructed and put into operation, and the hydraulic resources of the basin have been adjusted annually. By collecting hydrological data, re-calculating and determining the average annual water flow that can be used for power generation of the power station, and determining the overall plan for maintaining the existing power station dam and reforming other hydraulic structures, and then comparing and demonstrating the technical and economic plans, it is clear that the power station The total installed capacity and the number of units were optimized, new and high-efficiency hydro-generator units were selected, and the operation plan was formulated scientifically and rationally. After the renovation, the average annual power generation of the power station was 492% of that before the renovation.

The soft rock and wet slopes increase landslides over 50 m long creep slide and risk assessment for long steep slide in Şırnak open-pit coal mining should be searched in asphaltite quarries. The Avgamasya quarries No1 and 2 at critical depths and road bench sites in Şırnak, reaching over 120 m height with 60–65° shale slopes, developing major creep factors and other factors for landslide in the deep quarry locations is resulting debris rock falling or free sliding. The pore pressure measurements by measurements of water levels in four wells and water flow counting as the mining safety in recent years. This research provided rock slope stability patterns and crack propagation control of the hazardous location and formation cracks. The stages of creep experimentation explored the geophysical characteristics and thaw and freeze testing of rock samples. For this aim, two different long sliding areas with similar geoseismical conditions, two main analyzing methods, and patterns of researches were developed. Firstly, data on crack propagation in situ rock shale faces over certain time periods were determined. Displacement measurements over highly saturated shale—limestone contacts over the base of crack counting in a meter scale such as Rock Quality Designation (RQD) scoring of drilling logs. Secondly, hydrological water level logs were taken into consideration. On the other hand, due to that creep effect over freeze crack propagation unseen cause instability over wet sliding surfaces over 50 m, long sliding surface matter over slopes, poly linear or circle type creep sliding or rock tumbling falling failure types, and GEO5 slope stability, slice analysis will be advantageous instead of Finite Element Method (FEM) method.

<em>Abstract</em>.—The Brazos River crosses eight ecoregions on its journey from New Mexico through the heart of Texas to the Gulf of Mexico. This diverse stream ecosystem supports at least 85 fish species, many of which—including two endangered, migratory, pelagic broadcast-spawning cyprinids, Smalleye Shiner <em>Notropis buccula </em>and Sharpnose Shiner <em>N. oxyrhynchus</em>—have life histories that track the natural flow regime. These two shiners were listed as endangered in part because of severe range reductions that left each with one viable population in the upper Brazos River. Given their short life span, a single adverse event, such as a persistent drought of two consecutive years, could lead to extinction. This concern was nearly realized in 2011 when a record drought and heatwave resulted in complete reproductive failure of these species, which led to rescue efforts for imperiled shiners confined to drying pools. Seventeen major reservoirs control streamflow and create distinct, disconnected fragments in the Brazos River basin. Long-term ecological studies have provided a strong science foundation for guiding water and environmental flow management and watershed conservation. Implementation of both upland and riparian best management practices in the upper Brazos River watershed, including management of invasive saltcedar <em>Tamarix </em>spp., seeks to improve habitat for fish and wildlife. Hydrological monitoring and modeling is being conducted to evaluate the potential for saltcedar control to improve base flows. Identification of stream reaches most threatened by drying and where aquifer pumping may reduce groundwater inflows to streams is the focus of ongoing research on groundwater–surface water relationships. Fish passage barriers hinder successful recruitment, migration, and recolonization of prairie fishes. Removal and mitigation of barriers, as appropriate, will be critical to restoring ecological functions and connectivity required for migratory fishes. Research on propagation and repatriation of prairie fishes is needed to inform conservation and recovery efforts. A watershed-scale, multidisciplinary approach coordinated across borders and among entities is critical to ensure conservation efforts result in the persistence of native fishes in the Great Plains, including the Brazos River.

<em>Abstract.</em>—The Alabama River system, comprising the Alabama, Coosa, and Tallapoosa subsystems, forms the eastern portion of the Mobile River drainage. Physiographic diversity and geologic history have fostered development in the Alabama River system of globally significant levels of aquatic faunal diversity and endemism. At least 184 fishes are native to the system, including at least 33 endemic species. During the past century, dam construction for hydropower generation and navigation resulted in 16 reservoirs that inundate 44% of the length of the Alabama River system main stems. This extensive physical and hydrologic alteration has affected the fish fauna in three major ways. Diadromous and migratory species have declined precipitously. Fish assemblages persisting downstream from large main-stem dams have been simplified by loss of species unable to cope with altered flow and water quality regimes. Fish populations persisting in the headwaters and in tributaries to the mainstem reservoirs are now isolated and subjected to effects of physical and chemical habitat degradation. Ten fishes in the Alabama River system (including seven endemic species) are federally listed as threatened or endangered. Regional experts consider at least 28 additional species to be vulnerable, threatened, or endangered with extinction. Conserving the Alabama River system fish fauna will require innovative dam management, protection of streams from effects of urbanization and water supply development, and control of alien species dispersal. Failure to manage aggressively for integrity of remaining unimpounded portions of the Alabama River system will result in reduced quality of natural resources for future generations, continued assemblage simplification, and species extinctions.

Abstract Recently, the elevated levels of seismicity activities in Western Canada have been demonstrated to be linked to hydraulic fracturing operations that developed unconventional resources. The underlying triggering mechanisms of hydraulic fracturing-induced seismicity are still uncertain. The interactions of well stimulation and geology-geomechanical-hydrological features need to be investigated comprehensively. The linear poroelasticity theory was utilized to guide coupled poroelastic modeling and to quantify the physical process during hydraulic fracturing. The integrated analysis is first conducted to characterize the mechanical features and fluid flow behavior. The finite-element simulation is then conducted by coupling Darcy's law and solid mechanics to quantify the perturbation of pore pressure and poroelastic stress in the seismogenic fault zone. Finally, the Mohr-coulomb failure criterion is utilized to determine the spatial-temporal faults activation and reveal the trigger mechanisms of induced earthquakes. The mitigation strategy was proposed accordingly to reduce the potential seismic hazards near this region. A case study of ML 4.18 earthquake in the East Shale Basin was utilized to demonstrate the applicability of the coupled modeling and numerical simulation. Results showed that one inferred fault cut through the Duvernay formation with the strike of NE20°. The fracture half-length of two wells owns an average value of 124 m. The brittleness index deriving from the velocity logging data was estimated to be a relatively higher value in the Duvernay formation, indicating a geomechanical bias of stimulated formation for the fault activation. The coupled poroelastic simulation was conducted, showing that the hydrologic connection between seismogenic faults and stimulated well was established by the end of the 38th stage completion for the east horizontal well. The simulated coulomb failure stress surrounding the fault reached a maximum of 4.15 MPa, exceeding the critical value to cause the fault slip. Hence the poroelastic effects on the inferred fault were responsible for the fault activation and triggered the subsequent ML 4.18 earthquake. It is essential to optimize the stimulation site selection near the existing faults to reduce risks of future seismic hazards near the East Shale Basin.

The Weather and External Forces hazard (WEF) is considered in ASME B31.8 as a non-time-dependent hazard due to its random nature and the high uncertainty of the effects on pipelines given the occurrence of natural events, especially associated with hydro and geotechnical processes. Although there is a wide range of events associated with geological, hydrological and hydraulic conditions (among other things) that can affect a certain infrastructure, only a limited number of these geohazards can cause direct damage to hydrocarbon transportation infrastructure. The identification and understanding of a ground failure process and its association with the susceptibility or physical fragility of the pipeline facing the potential adverse effects of a hazard event, allow to estimate the conditional probability of pipeline failure under loading stresses induced by the event and to estimate the actions needed to mitigate this hazard with methodologies ranging from approaches of structured expert knowledge to methods of structured analysis that incorporate incorporating subsurface investigation, detailed study of the results from terrain monitoring, pipeline and triggering agents through mechanical modeling. This document presents a technical proposal for the management of geohazards which, due to the nature and characteristics of the instability processes and its relation with the activity of triggering agents, and the vulnerability of the pipeline, allow them to be analyzed as time dependent.

Abstract Objectives/Scope Steam injection in diatomite reservoirs results in permeability changes owing to fracture propagation, and compaction as a result of thermal effects and pressure changes during injection and production. The purpose of this work is to evaluate these coupled thermal, hydrological, and mechanical (THM) processes over several years of cyclic steam injection and production. A single well model in a diatomite reservoir was created to evaluate these processes at a higher resolution near wellbore than used in a 3-D reservoir-scale model. Methods, Procedures, Process Simulations include tensile failure, shear failure with simultaneous shear on multiple planes, coupling of porosity and permeability changes with multiphase flow, and diatomite compaction with temperature and effective stress. Initial isotropic horizontal stresses are 1.0375 of vertical (azimuthal average, part of San Joaquin Valley). Injection interval (437-528 m) pressure is fixed, 6.3 MPa, 930 psi (injection), and ~4 MPa (production), with a soak period between injection and production. Three degree dilation on shearing is assumed. To the extent that fracture opening is tensile, fractures close on fluid pressure drop, but shear components remain. Permeability changes due to mechanical failure are simulated using a cubic law. Results, Observations, Conclusions During injection over multiple cycles, the diatomite surrounding the well is heated to over 250 °C and pressurized by the injected steam. During soak (shut-in) and subsequent production, pressure drops, dropping the boiling point, inducing further vaporization. Geomechanical changes show tensile opening accompanied by a greater amount of shearing. Total shearing increases with each injection cycle, resulting in a greater porosity increase from shearing than tensile opening. Fracture propagation was limited to the diatomite reservoir and did not penetrate the caprock. Novel/Additive Information Inclusion of an empirical effective stress/temperature diatomite compaction law together with porosity and permeability changes due to mechanical failure more closely models the mechanics of cyclic steaming of diatomite.

Abstract The recent seismicity rate increase in Fox Creek is believed to be linked to the hydraulic fracturing operations near the region. However, the spatiotemporal evolution of hydraulic fracturing-induced seismicity is not well understood. Here, a coupled approach of geology, geomechanics, and hydrology is proposed to characterize the spatiotemporal evolution of hydraulic fracturing-induced seismicity. The seismogenic faults in the vicinity of stimulated wells are derived from the focal mechanisms of mainshock event and lineament features of induced events. In addition, the propagation of hydraulic fractures is simulated by using the PKN model, in combination with inferred fault, to characterize the possible well-fault hydrological communication. The original stress state of inferred fault is determined based on the geomechanics analysis. Based on the poroelasticity theory, the coupled flow-geomechanics simulation is finally conducted to quantitatively understand the fluid diffusion and poroelastic stress perturbation in response to hydraulic fracturing. A case study of a moment-magnitude-3.4 earthquake near Fox Creek is utilized to demonstrate the applicability of the coupled approach. It is shown that hydraulic fractures propagated along NE45° and connected with one North-south trending fault, causing the activation of fault and triggered the large magnitude event during fracturing operations. The barrier property of inferred fault under the strike-slip faulting regime constrains the nucleation position of induced seismicity within the injection layer. The combined changes of pore pressure and poroelastic stress caused the inferred fault to move towards the failure state and triggered the earthquake swarms. The associated spatiotemporal changes of Coulomb Failure Stress along the fault plane is well in line with the spatiotemporal pattern of induced seismicity in the studied case. Risks of seismic hazards could be reduced by decreasing fracturing job size during fracturing stimulations.

Italy is notoriously exposed to several natural hazards, from hydrological to volcanic and, above all, to seismic activity that affects a large part of the national territory. Historically the devastating effects of tsunamis have also been recorded, despite the peninsula is confined in the Mediterranean basin (i.e. Messina earthquake in 1908, and more recent the activity of the undersea volcano “Marsili”). Since Italy is particularly exposed to such hazards, many research institutions are involved in campaigns about monitoring, prevention and mitigation of the effects of such phenomena, with the aim to secure and protect human lives, and secondly, the remarkable cultural heritage. The present paper will first make a brief excursus on the main Italian research projects aimed at the mitigation of environmental disasters, referring to projects of national and international relevance, being implemented, such as the MOSE (for the containment of the tides and of high water, for the preservation of cultural and artistic heritage of Venice and of the entire ecosystem of the lagoon); the research in earthquake-resistant structures performed for instance by ENEA and finally the COSMO-SkyMed (CSK) program of the Italian Space Agency (ASI), which has among its purposes the environmental monitoring and surveillance applications for the management of exogenous, endogenous and anthropogenic risks. Furthermore in the paper, it will be described some new ideas concerning the use of smart materials and structures capable of self-monitoring and self-diagnosis of the risk of failure and adapting itself to environmental condition variations, in order to avoid catastrophic effects, thanks to an integrated network of sensors and actuators.

Geohazards are threats of a geological, geotechnical, hydrological, or seismic/tectonic nature that may negatively affect people, infrastructure and/or the environment. In a pipeline integrity management context, geohazards are considered under the time-independent threat category of Weather-related and Outside Force in the American standard ASME B31.8S. Geotechnical failure of pipelines due to ground movement is addressed in Annex H and elsewhere in the Canadian standard CSA-Z662. Both of these standards allow flexibility in terms of geohazard assessment as part of pipeline integrity management. As a result of this flexibility, many systems for identifying, characterizing, analyzing and managing geohazards have been developed by operators and geotechnical engineering practitioners. The evolution of these systems, and general expectations regarding geohazard assessment, toward quantitative geohazard frequency assessment is a trend in recent pipeline hearings and regulatory filings in Canada. While this trend is intended to frame geohazard assessment in an objective and repeatable manner, partitioning the assessment into a series of conditional probability estimates, the reality is that there is always an element of subjectivity in assigning these conditional probabilities, requiring subject matter expertise and expert judgment to make informed and defensible decisions. Defining a specific risk context (typically loss of containment from a pipeline) and communicating uncertainty are important aspects of applying these types of systems. Adoption of these approaches for alternate risk contexts, such as worker safety during pipeline construction, is challenging in that the specific geohazards and threat scenarios considered for long-term pipeline integrity may or may not adequately represent all credible threats during pipeline construction. This paper explores the commonalities and differences in short- and long-term framing of geohazard assessment, and offers guidance for extending geohazard assessment for long-term pipeline integrity to other contexts such as construction safety.

As the pipeline system of TransCanada Pipelines Ltd. (TransCanada) ages, cover at water crossings is continuously being adjusted to dynamic changes in weather patterns and local water crossing hydraulic characteristics. In an increased asset base of over 37 000 km of pipeline, this creates challenges to find and remediate crossings with high risks while maintaining the integrity of the whole system. A methodology has been developed to address the increasing demands of fiscal responsibility and pipeline integrity. The Scour Hazard Database Model (SHDM) provides the necessary tool to provide solutions to both of these challenges. The SHDM provides a stand alone prioritisation tool that is updateable and transparent. It can alert TransCanada to both immediate and potential pipeline exposures, in order that reactive and proactive solutions can be initiated. The SHDM contains descriptive pipeline information, local hydrologic data, channel hydraulic information, and scour hazard logic for over 2350 river and creek crossings throughout Canada. This information is used to produce a final rating value for comparing the potential for vertical and lateral pipeline exposures at each crossing. The vertical scour logic considers age of the crossing, modelled scour, natural degradation and any remedial work to determine the rating value. The lateral erosion logic uses channel form, location, lateral cover distances between the thalweg and pipeline, stream power, age of the crossing, and any remedial work to develop the lateral scour rating value. Furthermore, the exposed pipes are evaluated based on the potential failure mechanisms to determine failure probability. Included in the failure analysis are lateral stability, impact of debris, and fatigue. The failure probability and the consequence of the failure are used to rank the crossings and identify the requirement for maintenance activities.

The US Army Corps of Engineers (USACE) operates, maintains, and manages more than $232 billion worth of the Nation’s water resource infrastructure. Using the Operational Condition Assessment (OCA) system, the USACE allocates limited resources to assess conditions and maintain assets in efforts to minimize risks associated with asset performance degradation. Currently, OCAs are conducted on each component within a facility every 5 years, regardless of the component’s risk contribution. The analysis of risks associated with Flood Risk Management (FRM) facilities, such as dams, includes considering how the facility contributes to its associated FRM watershed system, understanding the consequences of degradation in the facility’s performance, and calculating the likelihood that the facility will perform as expected given the current OCA condition ratings of critical components. This research will develop a scalable methodology to model the probability of failure of components and systems that contribute to the performance of facilities in their respective FRM systems combined with consequences derived from hydrological models of the watershed to develop facility risk scores. This interim report documents the results of the first phase of this effort, stakeholder analysis and literature review, to identify candidate approaches to determine the probability of failure of a facility.

The US Army Corps of Engineers (USACE) operates, maintains, and manages over $232 billion worth of the Nation’s water resource infrastructure. Using Operational Condition Assessments (OCA), the USACE allocates limited resources to assess asset condition in efforts to minimize risks associated with asset performance degradation, but decision makers require a greater understanding of those risks. The analysis of risk associated with Flood Risk Management assets in the context of its associated watershed system includes understanding the consequences of the asset’s failure and a determination of the likelihood that the asset will perform as expected given the current OCA ratings of critical components. This research demonstrates an application of a scalable methodology to model the probability of a dam performing as expected given the state of its subordinate gates and their components. The research team combines this likelihood with consequences generated by the application of designed simulation experiments with hydrological models to develop a measure of risk. The resulting risk scores serve as an input for an optimization program that outputs the optimal set of components to conduct OCAs on to minimize risk in the watershed. Proof-of-concept results for an initial case study on the Jennings Randolph Dam are provided.

Maintenance of roadside ditches is important to avoid localized flooding and premature failure of pavements. Scheduling effective preventative maintenance requires mapping of the ditch profile to identify areas requiring excavation of long-term sediment accumulation. High-resolution, high-quality point clouds collected by mobile LiDAR mapping systems (MLMS) provide an opportunity for effective monitoring of roadside ditches and performing hydrological analyses. This study evaluated the applicability of mobile LiDAR for mapping roadside ditches for slope and drainage analyses. The performance of alternative MLMS units was performed. These MLMS included an unmanned ground vehicle, an unmanned aerial vehicle, a portable backpack system along with its vehicle-mounted version, a medium-grade wheel-based system, and a high-grade wheel-based system. Point cloud from all the MLMS units were in agreement in the vertical direction within the ±3 cm range for solid surfaces, such as paved roads, and ±7 cm range for surfaces with vegetation. The portable backpack system that could be carried by a surveyor or mounted on a vehicle and was the most flexible MLMS. The report concludes that due to flexibility and cost effectiveness of the portable backpack system, it is the preferred platform for mapping roadside ditches, followed by the medium-grade wheel-based system. Furthermore, a framework for ditch line characterization is proposed and tested using datasets acquired by the medium-grade wheel-based and vehicle-mounted portable systems over a state highway. An existing ground filtering approach is modified to handle variations in point density of mobile LiDAR data. Hydrological analyses, including flow direction and flow accumulation, are applied to extract the drainage network from the digital terrain model (DTM). Cross-sectional/longitudinal profiles of the ditch are automatically extracted from LiDAR data and visualized in 3D point clouds and 2D images. The slope derived from the LiDAR data was found to be very close to highway cross slope design standards of 2% on driving lanes, 4% on shoulders, as well as 6-by-1 slope for ditch lines. Potential flooded regions are identified by detecting areas with no LiDAR return and a recall score of 54% and 92% was achieved by the medium-grade wheel-based and vehicle-mounted portable systems, respectively. Furthermore, a framework for ditch line characterization is proposed and tested using datasets acquired by the medium-grade wheel-based and vehicle-mounted portable systems over a state highway. An existing ground filtering approach is modified to handle variations in point density of mobile LiDAR data. Hydrological analyses, including flow direction and flow accumulation, are applied to extract the drainage network from the digital terrain model (DTM). Cross-sectional/longitudinal profiles of the ditch are automatically extracted from LiDAR data, and visualized in 3D point clouds and 2D images. The slope derived from the LiDAR data was found to be very close to highway cross slope design standards of 2% on driving lanes, 4% on shoulder, as well as 6-by-1 slope for ditch lines. Potential flooded regions are identified by detecting areas with no LiDAR return and a recall score of 54% and 92% was achieved by the medium-grade wheel-based and vehicle-mounted portable systems, respectively.