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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Propagation of Radar Rainfall Uncertainties into Urban Flood Predictions: An Application in Phoenix, AZ

January 2020 (has links)
abstract: The Phoenix Metropolitan region is subject to intense summer monsoon thunderstorms that cause highly localized flooding. Due to the challenges in predicting these meteorological phenomena and modeling rainfall-runoff transformations in urban areas, the ability of the current operational forecasting system to predict the exact occurrence in space and time of floods in the urban region is still very limited. This thesis contributes to addressing this limitation in two ways. First, the existing 4-km, 1-h Stage IV and the new 1-km, 2-min Multi-Radar Multi-Sensor (MRMS) radar products are compared using a network of 365 gages as reference. It is found that MRMS products consistently overestimate rainfall during both monsoonal and tropical storms compared to Stage IV and local rain gauge measurements, although once bias-corrected offer a reasonable estimate for true rainfall at a higher spatial and temporal resolution than rain gauges can offer. Second, a model that quantifies the uncertainty of the radar products is applied and used to assess the propagation of rainfall errors through a hydrologic-hydraulic model of a small urban catchment in Downtown Phoenix using a Monte Carlo simulation. The results of these simulations suggest that for this catchment, the magnitude of variability in the distribution of runoff values is proportional to that of the input rainfall values. / Dissertation/Thesis / Masters Thesis Civil, Environmental and Sustainable Engineering 2020
22

Riverine flooding using GIS and remote sensing

Dambe, Natalia 30 April 2020 (has links)
Floods are caused by extreme meteorological and hydrological changes that are influenced directly or indirectly by human activities within the environment. The flood trends show that floods will reoccur and shall continue to affect the livelihoods, property, agriculture and the surrounding environment. This research has analyzed the riverine flood by integrating remote sensing, Geographical Information Systems (GIS), and hydraulic and/or hydrological modeling, to develop informed flood mapping for flood risk management. The application of Hydrological Engineering Center River Analysis System (HEC RAS) and HEC HMS models, developed by the USA Hydrologic Engineering Center of the Army Corps of Engineers in a data-poor environment of a developing country were successful, as a flood modeling tools in early warning systems and land use planning. The methodology involved data collection, preparation, and model simulation using 30m Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM) as a critical data input of HEC RAS model. The findings showed that modeling using HEC-RAS and HEC HMS models in a data-poor environment requires intensive data enhancements and adjustments; multiple utilization of open sources data; carrying out multiple model computation iterations and calibration; multiple field observation, which may be constrained with time and resources to get reasonable output.
23

Posouzení vybrané části stokové sítě v urbanizovaném území / Assessment of selected part of sewer network in urbanized area

Köhler, David January 2020 (has links)
The aim of the thesis is to assess the current state of sewerage of the site of interest in Ostrava and to suggest a possible renewal or extension of the sewer network. The work is divided into accompanying report, technical report, hydrotechnical calculations and drawing documentation. The assessment consists of determination of the technical state of selected sewers, hydraulic assessment of the sewer network with a proposal of possible measures and economic evaluation of these measures. In the part of hydrotechnical calculations creation of hydraulic model in program MIKE URBAN is described, including process of calibration and simulation of individual proposed variants of renewal or extension of sewer network of the locality of interest.
24

Modelación hidráulica de la red de distribución de agua potable en la localidad de Paucartambo - Cusco / Hydraulic modeling of the drinking water distribution network in the town of Paucartambo- Cusco

Valenzuela Peña, Mauricio Elias, Orrillo Cruz, Gianmarco Anthony 23 October 2019 (has links)
En la actualidad, la falta de planificación y control que existe en el desarrollo de proyectos de abastecimiento de agua potable es un factor determinante en la presencia de deficiencias en el funcionamiento de las redes de distribución en términos de continuidad y calidad de servicio. Esta investigación, haciendo uso del modelamiento hidráulico, busca evaluar el comportamiento de la red de distribución de agua de la localidad de Paucartambo-Cusco, con el fin de proponer soluciones y mejoras que ayuden a controlar y disminuir las deficiencias tanto actuales como futuras que pudieran presentarse. Primeramente, se planteó la modelación de la red en estado actual, comportamiento real, verificando los distintos factores de diseño, así como la consideración del análisis de agua no facturada (ANF). En este se encontró que las deficiencias del parque de medidores correspondientes a las conexiones activas generan un elevado porcentaje de ANF, lo que afecta el funcionamiento de la red en términos de continuidad y servicio. Para evaluar su influencia en una red futura se realizó un balance oferta-demanda. Bajo esta premisa se presentó una propuesta de red futura en un escenario donde se controla el porcentaje de ANF mediante la implementación de planes y acciones de manejo, logrando reducir la dotación existente (302.38 lt/hab/dia) hasta valores más acordes con el R.N.E (180 lt/hab/dia) significando una disminución del porcentaje de ANF de 68% hasta 40.47% aproximadamente, lo que garantiza un funcionamiento más óptimo tanto hidráulica como económicamente frente a un escenario que no considere el análisis de ANF. / At present, the lack of planning and control that exists in the development of potable water supply projects is a determining factor in the presence of deficiencies in the operation of distribution networks in terms of continuity and quality of service. This research, using hydraulic modeling, seeks to evaluate the behavior of the water distribution network of the town of Paucartambo-Cusco, in order to propose solutions and improvements that help control and reduce both current and future deficiencies that could introduce oneself. First, the modeling of the network in the current state, real behavior, verifying the different design factors, as well as the consideration of the non-invoiced water analysis (ANF) was considered. In this, it was found that the deficiencies of the meter stock corresponding to the active connections generate a high percentage of ANF, which affects the operation of the network in terms of continuity and service. To assess its influence on a future network, an offer-demand balance was made. Under this premise, a proposal for a future network was presented in a scenario where the percentage of ANF is controlled through the implementation of management plans and actions, reducing the existing endowment (302.38 lt / hab / day) to values ​​more in line with the RNE (180 lt / hab / day) meaning a decrease in the percentage of ANF from 68% to approximately 40.47%, which guarantees a more optimal operation both hydraulically and economically compared to a scenario that does not consider the ANF analysis. / Tesis
25

Decreased scour on an external river bend using two-dimensional numerical model, in la Perla-Florida and Cantagallo sectors of Rímac river

Ravines, Mauricio Bazan, Vargas, Jorge Coronado, De Bazan, Sissi Santos Hurtado 30 September 2020 (has links)
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / This paper, evaluates a proposal for an external bend fluvial erosion control, using submerged vanes as velocity and shear stress control, verifying its effectiveness by modeling in Iber to calculate the scour produced by discharges with different return periods. The results indicate that the velocity, shear stress and scour decrease along the curve, due to submerged vanes.
26

Analysis of the Sediment Transport Capabilities of TUFLOW

Jenkins, Cameron G. 07 August 2009 (has links) (PDF)
The need to know how river morphology changes due to sedimentation is increasingly important as we attempt to predict future events. Engineers use numeric models to predict effects of changed morphology on river systems. The numerical model Two-dimensional Unsteady Flow (TUFLOW) has recently added, and is continually improving, its capability to model sediment transport in rivers and coastal systems. This paper evaluates the new tools for modeling sediment transport presently contained within TUFLOW and compares these tools with analytical and laboratory case studies. Currently TUFLOW simulates combined bed and suspended load transport of noncohesive sediments under the effect of currents using the Van Rijn method. New TUFLOW capabilities which have not been extensively tested before include recognized sediment transport relationships such as those of Meyer-Peter and Mueller, Bagnold, and Ackers & White. It is important to note that the software evaluated herein is a snapshot of a continuing software development process. The aim of the TUFLOW developers is to address any shortcomings outlined in this paper where feasible. Eleven different test cases are modeled in the Surface-water Modeling System (SMS) software. The test cases are designed to examine how well TUFLOW simulates sediment transport modeling with channels of varying degrees of slope and contractions. Eight of the test cases are taken from Analysis of the Sediment Transport Capabilities of FESWMS. Three cases simulate a simple flume with varying midsection slopes. Four cases use a simple flume with no slope and different contractions: a short abrupt contraction, a long abrupt contraction, a long gradual contraction, and a wide contraction. Two of the test cases are from laboratory flume experiments that were performed at St. Anthony Falls Laboratory. The last test case consists of a river entering a reservoir. The results show that TUFLOW is presently capable of representing sediment transport and morphology reasonably on moderate and shallow slopes and channels with contractions. However, more work is required to improve TUFLOW's morphological capabilities on steep slopes when hydraulic jumps are present. The results show TUFLOW can handle long term simulations. The results show that TUFLOW is not capable at this time of recreating the lab flumes and more features need to be added to accurately portray the flumes. TUFLOW did show perturbations, common for semi-coupled models, in the results for certain test cases. Filtering, a common way of removing perturbations was implemented and gave varying results. The developers are in the process of developing a more advanced scheme for filtering.
27

Evaluating an increased spill regime as a management tool to improve downstream passage of salmon smolt / Utvärdering av ökat spill som en förvaltningsåtgärd för att förbättra nedströms passage för laxsmolt

Hansson, Mattias January 2022 (has links)
The anadromous Atlantic salmon (Salmo salar) is dependent on river connectivity to reach spawning and rearing habitats in rivers. Most rivers are today fragmented by artificial barriers such as hydroelectric powerplants (HEP) which impede this migratory movement. As an effort to mitigate river fragmentation, upstream passages have been built at some impediments, but passage facilitating downstream migration has been commonly disregarded until recently. The increased mortality associated with downstream movement through hydroelectric turbines have caused population declines and extirpation in some areas. A common first measure to improve downstream passage is to increase spill discharge during critical time periods. In this study we aim to evaluate the efficiency of increased spill as a management tool and investigate the effect on environmental and physiological factors on fish passage in River Mörrumsån, Sweden. This was done by tracking salmon smolt using high resolution acoustic telemetry and time-to-event models. The results were then further explored in relation to 2D-hydraulic models of different spill scenarios. The results show that increasing the spill at Upper Hemsjö HEP resulted in a relatively high impediment passage efficiency. Spill gate passage was best explained by the proportion of spill in relation to intake channel discharge and diel period. Increased spill and nights without ambient lights where positively associated with spill gate passage rate. Increased levels of spill seamed to increase the attraction to the spill gate passage zone which could be explained by the increased area of flow directed toward the spill gate observed in the hydraulic model, showing the usefulness of hydraulic models as an additional tool in evaluation and planning of remedial measures. The result in this study shows that increased spill can be an effective way to ameliorate river fragmentation, however this should be put in relation to the goal of the mitigation measure as increased spill only creates a temporary solution for a permanent problem. / Den anadroma Atlantlaxen (Salmo salar) är beroende av fria vandringsvägar mellan hav och älv, då de nyttjar olika habitat under olika delar av livscykeln. Laxen vandra mellan dess tillväxt område i havet och deras parnings samt uppväxt område i älvar. Det flesta vattendrag är i dag fragmenterade av artificiella barriärer som tillexempel vattenkraftverk. För att minska de negativa effekterna av dessa har uppströmspassager konstruerats, men passage för nedströmsvandring har ofta åsidosatts. Den ökade dödligheten associerad med nedströmspassage genom vattenkraftturbiner har haft kraftig påverkan på många populationer. En vanlig första åtgärd för att förbättra nedströmspassagen är att öka mängden vatten som spills under kritiska perioder, som laxsmoltens nedströmsvandring under våren. Målet med denna studie är att utvärdera ökat spill som en förvaltningsåtgärd och analyserar hur olika miljöfaktorer och fysiologiska faktorer påverkar passageeffektiviteten för nedströmsmigrerande smolt. Detta undersöktes genom att använda högupplöst hydroakustisk telemetri för att spåra fisken och genom att analysera rörelsen med hjälp av time-to-event modeller. Tvådimensionella hydrauliska modeller skapades för att ytterligare utforska resultaten i förhållande till olika spill regimer. Den ökade spill regimen resulterade i relativt hög passage effektivitet förbi hindret. Passage genom spill porten kunde bäst förklaras av period på dygnet samt proportionen av spill i förhållande till flödet genom intagskanalen. Ökad passage effektivitet kunde associeras med passage under natten när belysningen på dammen var avstängd samt ökad andel spill i förhållande till flödet genom intagaskanalen. Ökat spill verkade resultera i ökad attraktion till området framför spill porten, vilket skulle kunna förklaras av den ökade ytan av vatten som rör sig mot spill porten som observerades i den hydrauliska modellen. Dessa resultat visar hur hydrauliskmodellering kan användas som ytterligare ett förvaltningsverktyg för att utvärdera eller planera förbättringsåtgärder. Resultaten Vidare indikerar studien att ökat spill är en metod som kan förbättrar laxsmoltens möjligheter till nedströms passage, detta bör dock sättas i relation till vad som är målet med åtgärden, ökat spill gynnar ett fåtal arter under en begränsad tid på året. Således kvarstår problemet med begränsad konnektivitet i vattendraget under resterande delar av året.
28

Assessing the Spawning Potential of Grass Carp in the Sandusky River Under Varying Conditions

Embke, Holly Susan 19 October 2017 (has links)
No description available.
29

A Dam Conundrum: The Role of Impoundments in Stream Flow Alteration

Brogan, Connor O'Beirne 12 September 2018 (has links)
Over the past century, the world's rivers have become increasingly impounded to combat water scarcity and fossil-fuel reliance. Large dams have faded from popularity due to their adverse environmental effects, but small ponds and reservoirs continue to be constructed at high rates. Due to limited data regarding their size and flow, it has been difficult to assess how these smaller impoundments impact rivers. This study combined rainfall runoff data from the Chesapeake Bay Model with the unique routing framework of VA Hydro to create a simplistic hydrologic model capable of analyzing impoundment-induced flow alteration. Using standard design techniques and satellite imagery, a methodology was developed to build realistic stage-storage-discharge relationships for small and large impoundments. Eleven impoundments of the Difficult Run watershed were modeled within VA Hydro to assess their cumulative impact on downstream flow. Multiple models were created with different active impoundments and run for the full model period, 1984 - 2005. Flow alteration increased significantly with additional impoundments. Peak flows were attenuated as water was stored behind outlets, but median flows were increased as this water was slowly released. Average storm duration increased due to extended rising and falling limbs caused by impoundment outlets. Headwater channels increasingly ran dry, decreasing extreme low flows due to impoundment evaporation. Large reservoirs had a greater impact on median flows, but smaller ponds dominated low flow alteration. These results suggest that traditional hydrologic assumptions and metrics may be incapable of analyzing a changing flow regime without explicitly considering small and large impoundments upstream. / Master of Science / At first look, dams are an excellent solution to water scarcity and energy independence. They trap clean water and direct it through turbines. Unfortunately, their installation and operation creates many negative environmental impacts by fundamentally altering downstream channels, leading to a loss of fish vitality and river function. Large dam construction has decreased in the US because of these effects, but small dams continue to be built at high rates due to growing agricultural and stormwater demands. Their impact on rivers is less understood due to limited data availability regarding their size and function. This experiment used standard design techniques and widely available satellite data to create a representative model for dams of all size. Multiple tests were run, progressively increasing the number of dams within a watershed and analyzing their impact on downstream flow. With increased impoundment, high floods decreased in magnitude. However, more-typical medium flows increased. River flow became more static, with less extreme floods and more medium flows. The modeled dams greatly decreased drought flows as trapped water evaporated and decreased outflow. This impact was particularly noticeable in ponds that drained only a small area as they took longer to refill after drying. Larger dams more greatly impacted medium flows. These results contribute significantly to water availability prediction by more realistically representing dam processes. Although more work is needed to refine the impoundment modeling strategy, this study has effectively demonstrated that small and large dams affect flow in different manners and need to be accounted for accordingly.
30

Avgränsningsmetodens betydelse för hydraulisk modellering av spill- och dagvattennät / The effects of delineation metods on hydraulic modelling of wastewater networks

Johansson, David January 2019 (has links)
Metoden för att avgränsa modellområdet i delavrinningsområden med homogena hydrologiska parametrar inför hydrauliska ledningsnätssimuleringar kan vara tidsödande. Olika metoder och tillvägagångssätt finns att tillgå, men kunskapen om hur valet av avgränsningsmetod påverkar simuleringsresultaten är begränsad.   I examensarbetet undersöktes hur fyra enkla avgränsningsmetoder, i jämförelse med två detaljerade metoder, påverkade en hydraulisk simulering av en regnhändelse på sex olika modelluppsättningar av spill- och dagvattennät. De detaljerade metoderna byggde på information om markhöjder i kombination med byggnaders placering, medan de enklare metoderna byggde på information om markhöjder respektive Thiessenpolygoner. Avgränsningsmetoderna testades för en dagvattenmodell, en kombinerad spill- och dagvattenmodell, och fyra spillvattenmodeller. Alla modellparametrar förutom de associerade med delavrinningsområdena (bidragande yta, koncentrationstid) hölls konstanta medan en regnhändelse med återkomsttid tio år och en maximal regnintensitet av 22,8 µm/s (82.1 mm/h) simulerades för varje avgränsningsmetod och modelluppsättning.    De olika metoderna gav upphov till skillnader i simulerat maximalt vattendjup i modelluppsättningarnas brunnar. De enklare metoderna tenderade att underskatta de simulerade vattendjupen och avvikelsen mot de detaljerade metoderna översteg 0,1 m, vilket utgjort en gräns för när avvikelsen får praktisk betydelse. Fler avvikelser erhölls uppströms i ledningsnätet och för modelluppsättningar med större avrinningsbildning. Inga entydigt upprepande förhållanden mellan metodernas påverkan på simuleringsresultaten mellan modelluppsättningarna fanns, varvid modellområdesegenskaper tros påverka effekten av vald avgränsningsmetod. Resultaten indikerade att det kan vara mer motiverat att använda enklare avgränsningsmetoder för spillvattenmodeller i förortsmiljö än för dagvattenmodeller i stadsmiljö, samt att metoder baserat på Thiessenpolygoner ger bättre överensstämmelse mot detaljerade metoder än de topografibaserade. / The method of delineating a model into sub-catchments with homogenous hydrological parameters, before performing hydraulic simulations, can be tedious work. Different approaches and methods for this purpose exist, but the understanding for how the choice of delineation method affects the modeling process and in the end the simulation results is limited.    This thesis explored how four simplified delineation methods, in comparison with two detailed methods, affected hydraulic simulation of a rain event on six different model set ups. The detailed methods were based on terrain analysis and property boundaries. The simplified methods were composed of twomethods based on terrain analysis of elevation models, and two methods based on Thiessen polygons. The delineation methods were applied on one stormwater model, one combined storm- and wastewater model, and on four wastewater models. All model parameters except for those associated with the sub-catchments (time of concentration, imperviousness) were kept constant as a scenario of a rain event with a return time period of 10 years and maximum intensity of 22.8 µm/s (82.1 mm/h) were simulated for every delineation method and model set up.   The different methods resulted in differences in simulated maximal water depth in the modelled manholes. The simplified methods tended to underestimate the water depth. Additionally, the deviation from the detailed methods exceeded 0.1m, which is a threshold value for when the deviations will be of practical importance. Greater deviations occurred upstream in the sewer system and for models with greater runoff volume. No unambiguous patterns were found between the methods and the model setups. Hence, the delineation methods cannot by themselves explain the observed deviation in the simulated water depths. The results indicate that it is more suitable to apply a simple method on a sewage model in a suburban area, than for a stormwater model in an urban area. In addition, the simplified methods based on Thiessen polygons showed more agreement with the detailed methods than the simple methods based on terrain analysis.

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