R-3 Repository :: Browsing by Author "Bedient, Philip"

Browsing by Author "Bedient, Philip"

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Addressing Uncertainty in Residential Damage Estimates from Tropical Cyclone Storm Surge, with a Focus on Variability in Structure Elevations
(2017-01-12) Irza, John Nicholas; Bedient, Philip
A residential storm surge damage model was developed for a coastal Texas county. The model was used to investigate uncertainty in damage estimates under varying initial assumptions of structure elevations. Results indicated that the model was highly-sensitive to such assumptions, and discrepancies between damage estimates approached $2 billion for some scenarios. A survey of home elevations within the county was conducted to correct the initial assumptions. After correction, variability between the estimates decreased significantly, and the results suggested commonly employed elevation assumptions may be prone to damage overestimation. Additional aspects of uncertainty were then incorporated into the model and an uncertainty analysis (UA) was performed with respect to assumptions of the spatial independence between model parameters. The UA results showed a large degree of variability between independence assumptions. Finally, a global sensitivity analysis of the model was performed with inconclusive results, as they varied by independence assumption.
Assessing Flood Mitigation Strategies Based on Quantification of Risk for Economically Disadvantaged Watershed in Houston
(2020-08-14) Gadit, Meera; Bedient, Philip
Increase in the frequency of flooding has become a major challenge for many big cities around the world. Policy and decision makers employ both structural and non-structural measures to achieve resilience against flooding, and flood risk maps can be a useful tool for evaluation of both kinds of strategies. Until now, policy makers have mainly been relying on floodplain maps (hazard maps) developed for a given frequency rainfall event (e.g. 100-yr event), which represent only the hydrologic and hydraulic response of the study area for the rainfall event. More information about the consequences of flooding can be presented through spatial risk maps, because they combine the probability of a hydrologic event, the extent of exposure to the event and vulnerability of the exposed area. One city that has been particularly affected by severe flooding in the past and especially within last few years is Houston, Texas. This thesis computes the economic risk for Greens Bayou Watershed located in northeastern Houston for a more comprehensive assessment of flood risk than what is currently done, and to better evaluate the effectiveness of suggested flood mitigation strategies. The computed risk maps depend upon the floodplain maps obtained through the hydrologic and hydraulic modeling. The modeling approach used to obtain the floodplain maps affects the ultimate evaluation of risk. Hence this thesis also compares the risk maps obtained through 1D and 2D hydraulic modeling. Although conducted for only one watershed in Houston, this risk analysis helps us understand the importance of using risk maps for better decision making to mitigate the consequences of flooding in general.
Characterization of Friction Reducer Properties in Oil-Field Operations
(2015-01-15) Bolanos Ellis, Valerie; Tomson, Mason B.; Alvarez, Pedro; Bedient, Philip; Tomson , Ross
Friction reducers are essential additives used to economically achieve the high pumping rates required for slickwater fracturing. Decreased friction reducer performance in high-TDS brines has been a major challenge for reusing produced water in hydraulic fracturing. Little work has been done to identify the specific parameters that affect polymeric friction reduction. This research uses friction flow loop experiments to characterize the performance of partially hydrolyzed polyacrylamide friction reducers in conditions relevant to the oil field. Polymer concentration and degree of hydrolysis effects on friction reduction are evaluated in the ranges of 0.25-2 gpt and 0-30%, respectively. The decrease in friction reducer performance is measured in brines up to 120,000 mg/L TDS with varying multivalent cation concentrations. The friction reducer interactions with Na+, Ca2+, Mg2+, Fe3+, and Al 3+ ions are individually assessed. The results are compared to experiments with a commercial friction reducer, and used to propose an empirical model to predict friction reducer performance based on water composition.
Coupled Ocean-Hydraulic Modeling for Socially Informed Compound Infrastructure Analysis in Clear Lake, TX
(2023-04-13) Weathington, Briggs Tomás; Bedient, Philip
With intensifying tropical cyclones and growing exposure along the coast, understanding and responding to coastal flood hazards is more important than ever. One response to this growing risk is the design and construction of massive resilient infrastructure projects such as the Galveston Bay Park Plan. Extensive modeling is necessary to predict the effects of such projects before investing the time and resources in their construction. However, the massive scale of hurricane systems makes resolving human-scale impacts difficult. To overcome this disparity of scale, many researchers have begun coupling large-scale oceanic hurricane models with high-resolution inland flooding models. This project presents an efficient one-way model coupling strategy incorporating storm surge data from ADCIRC into a 2D HEC-RAS model. This coupling strategy is applied to Houston’s Clear Creek watershed where it meets Galveston Bay to assess GBPP’s flood depth and extent reduction benefits in severe storm conditions. The finely detailed results of this model are then compared to Social Vulnerability Index data to assess the socioeconomic distribution of flood reduction.
Evaluating the Hydrodynamic Performance of Green and Gray Infrastructure in Urban Watersheds for the Greater Houston Region
(2016-08-11) Juan, Andrew; Bedient, Philip
Flooding is the costliest hazard in the United States. Among the many flood prone areas in the nation, the Greater Houston Region is considered one of the most vulnerable, due to high intensity rainfall, flat topography, high imperviousness, and poor infiltration. Traditionally, Houston’s flood control strategy involves the implementation of gray infrastructure (e.g., channelization and detention basins). However, even after spending billions of dollars on numerous flood reduction projects, Houston continues to suffer from flood damages. Houston’s severe flooding issue has prompted various efforts to develop new flood control strategies. One alternative is Green Infrastructure, or Low Impact Development (LID), which consists of land development strategies aiming to preserve predevelopment hydrology. Originally designed to improve water quality, LID has also been shown to attenuate flood flows. Despite its popularity in the Northeast and the Northwest, the flood reduction benefits of LID in the Greater Houston Region are poorly understood. Moreover, most currently available models capable of simulating site-scale LID features are applied to small-scale study areas, providing limited insight at the watershed-scale. To bridge these knowledge gaps, this research proposes a method to model two site-scale LID features: green roofs and rain gardens at the watershed level. The hydrologic performance of an experimental watershed-wide LID implementation at The Woodlands is evaluated using a distributed hydrologic model. The findings suggest that LID features can be used able to reduce peak flow and runoff volume for smaller magnitude and intensity storms, but has limited effects for larger, more intense events. For comparison, this research also examines the hydrodynamic performance of gray infrastructure at two different scales of implementation: a catchment-wide flood reduction project at Brays Bayou and a local drainage improvement at Harris Gully. Due to the difference in application scales, floodplain analyses of both studies reveal varying degrees of flood reduction benefits. By understanding the flood reduction potential and limitations of green and gray infrastructure, this research can help floodplain managers and local stakeholders in the proper selection of flood control strategies.
Improvements to the Characterization of Hurricane Flooding with Advanced Statistical and Numerical Modeling
(2017-12-19) Bass, Benjamin; Bedient, Philip; Griffin, Robert
Hurricanes have historically and continue to result in some of the most devastating natural disasters. Despite a wealth of research efforts since the active 2005 hurricane season (i.e. Katrina, Rita, Wilma), key questions related to hurricane flood characterization, mitigation, forecasts, and frequency remain under-explored. This dissertation addresses such research topics by combining several numerical models with hindcast, deterministic, and probabilistic methodologies to represent multiple hurricane flood hazards, including storm surge, rainfall-runoff, and interactions between these two sources of flooding (combined flooding). This thesis begins with the first numerical analysis of the performance and sensitivity of different hurricane storm surge indices, or simple parametric descriptors of hurricane characteristics, and their ability to represent a hurricane’s storm surge response. After Katrina (2005) several surge indices were proposed to replace the category-based Saffir-Simpson index, but these surge indices were either not evaluated or their performance relative to one another was determined inconclusive due to limited observational data. For this, and other projects in this thesis, the storm surge response of hurricanes was evaluated using the tightly coupled ADvanced CIRCulation (ADCIRC) and Simulating WAves Nearshore (SWAN) model (ADCIRC+SWAN). Findings from this research demonstrate the performance and sensitivity of different surge indices and can help guide the replacement of Saffir-Simpson categories with an improved hurricane storm surge index. In the second study of this thesis, storm surge dynamics are characterized in a complex bay environment to understand how variations in storm and environmental factors, including sea level rise and the potential erosion of barrier islands, influence flow dynamics across the various tidal inlets and barrier islands that make up Galveston Bay’s (the Bay’s) coastline. This research provides useful insight regarding the regional flood vulnerability of the Houston-Galveston region and how this flood vulnerability can effectively be reduced by focusing surge mitigation along specific sections of the Bay’s coastline. The third study in this thesis demonstrates that while a coastal barrier can prevent flood impacts from oceanic storm surge, significant storm surge can still develop within Galveston Bay itself, suggesting the additional need for multiple lines of defense strategies. This study proceeds to evaluate the hydrodynamic performance of several regional surge mitigation strategies, including designs that protect from oceanic storm surge as well as local surge that can develop within Galveston Bay itself. Analyses in this study goes beyond the typical 100-yr rule of thumb design by evaluating the performance of different strategies for several return period events under current as well as future sea level conditions. The final study of this thesis evaluates combined flooding in coastal watersheds due to rainfall-runoff associated with hurricanes and its interactions with storm surge. Such analysis is crucial given that rainfall associated flooding is still not represented in probabilistic forecasting and frequency (i.e. 100-yr floodplain) products despite causing ~27% of human fatalities during hurricane events. To fill this information gap, a rapid hurricane flood prediction system was developed to represent the combined flood response from hurricanes. The utility of this combined flood prediction system was then demonstrated by improving upon probabilistic hurricane flood forecasting and frequency products. In this thesis, numerical flood analysis was performed in coastal watersheds, a bay, and the open coast. By characterizing, forecasting, and evaluating different strategies to protect against hurricanes, the author hopes to not only advance the current state of hurricane science, but to additionally provide practical insight and tools to increase coastal resiliency.
Integrating Reservoir Operations and Flood Modeling with HEC-RAS 2D
(MDPI, 2020) Garcia, Matthew; Juan, Andrew; Bedient, Philip
Current free to use models developed by the United States Army Corps of Engineers (USACE) perform unique functions (e.g., hydrology, hydraulics, reservoir operations, and flood impact analysis) that are widely used in numerous studies and applications. These models are commonly set up in a framework that is limited to point source connections, which is problematic in regions with flat topography and complex hydrodynamics. The separate models need to be integrally linked and jointly considered for accurate risk communication and decision-making, especially during major storm events. Recently, Hurricane Harvey (2017) exposed the shortcomings of the existing framework in West Harris County, TX, where an insufficient understanding of potential flood risk and impacts contributed to the extensive flood damages sustained in the region. This work illustrates the possibility of using a single hydraulic model, HEC-RAS 2D, to perform all hydrologic, hydraulic, and reservoir operations modeling necessary for accurate flood impact assessments. Implications of this study include a simplification of the entire flood impact analysis, which could help future flood risk communication and emergency planning.
Mapping Dynamic Watershed Response Under Increasing Development Using HEC-RAS 2D: A Case Study of the Big Creek Watershed in Fort Bend County
(2022-04-18) Hoffmann, Elizabeth A; Bedient, Philip
The Big Creek Watershed located in Fort Bend County was severely inundated during Hurricane Harvey as 6,800 homes were damaged and 10,000 rescues were conducted. The Big Creek Watershed is an undeveloped, low-slope area that experiences the pressure of future development on the western frontier of Houston. Urbanization exacerbates inundation in flood prone areas, especially floodplains, as land use changes increase impervious surface area, decrease rainfall infiltration, and intensify flooding. Therefore, it is critical to understand how the floodplains in the Big Creek Watershed change as the area becomes more developed. A two-dimensional hydrodynamic model of the region was created in order to map the floodplains under current conditions and projected 2045 conditions. The model was calibrated using radar rainfall from storms occurring in May 2015, August 2017 (Hurricane Harvey), and May 2019, which each caused substantial peak discharges within the watershed. The validated model was used to create floodplain maps for 10-year, 25-year, 50-year, and 100-year design storms in both current and future land use scenarios. The modeled results demonstrated that urbanization increases the peak flows within the watershed, yet urbanization was not found to change the floodplain extent a notable amount (less than 5%). This work provides data and floodplain maps that demonstrate the effects of urbanization in the area and encourage officials to deter development in hazardous areas and mitigate flood risk for the community.
Modeling Flood Reduction of Nature-Based Channel Modifications in Houston, TX
(2023-04-19) Peeples, Amelia; Bedient, Philip
Urban flood risk is being exacerbated around the world due to increased runoff from development as well as increased rainfall intensity due to climate change. Houston, TX has historically relied on grey flood mitigation measures, but, due to recent flooding and rapid urbanization, Houston is still in need of additional flood mitigation. Other regions with high flood risk have successfully implemented large-scale nature-based flood mitigation regimes, such as the Room for the River project in the Netherlands. However, there have not been previous studies on how nature-based channel modifications would impact flood risk on previously highly engineered bayous in Houston. The purpose of this study is to model how river restoration, characterized by increasing floodplain volume and increasing vegetation, has the potential to reduce riverine flood risk in Houston. By testing a large array of channel restoration scenarios, the optimal channel modification design, vegetation, length, and location is determined to optimize floodplain reduction while considering diminishing returns associated with continued channel widening. The efficacy of this methodology was tested by modeling the present conditions as well as a suite of modified channel conditions of White Oak Bayou watershed using a 2D HEC-RAS model.
Novel Computational and Stochastic Methods for Characterizing Joint Flood Hazards under Extreme Hurricane Events
(2016-04-20) Torres, Jacob M.; Bedient, Philip
In the United States, coastal flood risk management is traditionally predicated on protecting against extreme hurricane-induced storm surge (expressed in annualized return periods). However, (1) hurricane storm surge and (2) hurricane rainfall-runoff are not mutually exclusive coastal flood hazards. Little research has emphasized the need for characterizing the joint physical surge-rainfall processes for enhancing our understanding of the coastal hydrologic landscape as it relates to resiliency. This investigation involves the collection of interconnected studies that provide a set of original research contributions to the body-of-knowledge. A key research component entails the coupled development and calibration of advanced numerical models for in-depth hydrodynamic analyses of complex discrete-event hurricane simulations. These models include an improved distributed hydrologic model for simulating large-scale watershed response from hurricane rainfall events; the utilization of a revalidated (2) finite element hydrodynamic model that couples Simulating WAves Nearshore with ADvanced CIRCulation (SWAN+ADCIRC) for quantifying storm surge and wave dynamics; and an (3) improved unsteady riverine hydraulic model for associating storm surge and rainfall-runoff momentum interactions at the Houston Ship Channel (HSC). The coupling of these models is driven by the need for a centralized numerical testbed for which complex hydrological processes at the coastal-riverine interface can be studied. Modeled storm types include historical, pseudo-synthetic, and fully-synthetic hurricanes, some of which involve a novel spatial and temporal translation of hurricane windfields and rainfall to the model domain. Derived insights on coupled surge-rainfall processes are applied to storm surge mitigation for the Houston Ship Channel (HSC) and Galveston Bay regions. The modeled concepts of storm surge barrier systems are also analyzed under 1-D (unsteady HEC-RAS) and 2-D modeling (SWAN+ADCIRC) frameworks. Overall, findings reveal how hurricanes producing relatively little storm surge but high rainfall can be comparable in flood potential to the inverse scenario of hurricanes producing high storm surge and little rainfall for a given location. This is owed to heterogeneous topologies of coastal watershed boundaries, and varies with hurricane landfall location. This relationship affects our ability to protect coastal communities from threats against downstream hurricane storm surge and upstream hurricane rainfall-runoff. The storm surge barriers modeled at the HSC and Galveston Bay are shown be hydraulically feasible for the scenarios analyzed. However, results show that structural barrier placement across relatively incised channels that drain coastal watersheds are more prone to complexities involving timing separations of peak storm surge and rainfall-runoff. This complexity is exacerbated when considering dynamic operations of surge barrier systems and highlights the importance for accurate hurricane flood forecasting. Equally vital towards a practical achievement of coastal resiliency are the continuous functionalities of critical and interconnected infrastructure systems during hazard events. This study investigates the feasibility of coupling physics-based models with graph theory for developing proxies on engineered performance for water distribution systems (WDS). Results show strong correlations can exist for certain graph theory metrics and WDS performance, thus improving its favorability as a practice-ready approach with broader insights on pipe network topologies that are more robust to coastal natural hazards and other disasters.
Quantifying Impacts of Development on Floodplain Evolution and Projections of Future Flood Hazard: Applications to Harris County, TX
(2018-04-19) Gori, Avantika; Bedient, Philip
This thesis investigates the impacts of urbanization patterns and development activity on evolving flood hazard in the Houston region. Characterized by mild topography and a climate prone to high-intensity rain events, as well as a regulatory atmosphere that has encouraged decades of urban sprawl, Houston serves as an ideal case study area to examine how historical development practices and future growth estimates impact riverine flood hazard. While it has been well-documented that urbanization can increase runoff volume and peak flows, there has been little research investigating urbanization impacts on floodplain extent. It is crucial to understand the relationship between development activity and floodplain evolution in order to characterize the effectiveness of existing flood management infrastructure as well as the impacts of regional development planning and policy. First, historical development impacts are examined in the Brays Bayou watershed by utilizing a physic-based hydrologic model and steady-state hydraulic model to evaluate changes in floodplain from 1970's to current conditions. Results indicate that historical development has resulted in severe increases in floodplain extent and exponential impacts to residential flood exposure. Next, an integrated framework that links land use projection modeling with hydrologic and hydraulic modeling is developed and applied to the Cypress Creek watershed to project increases in flood hazard associated with future development. Utilizing output from an urban growth model, future land use scenarios for the year 2050 are developed, and flood hazard projections are made through integrated hydrologic and 1D/2D hydraulic modeling. A novel methodology for representing on-site detention features, based on current county development regulations, is proposed and applied within the hydrologic modeling framework to ultimately produce realistic estimates of future flood hazard in Cypress Creek based on both regional patterns of development as well as site-scale development policies.
Quantifying risk reduction of flood mitigation measures for an unrban watershed in Houston, Texas.
(2019-04-19) Maulsby, Ferne E; Bedient, Philip
In this thesis, flood mitigation measures are evaluated using risk-based analysis in a fully developed urban watershed by quantifying expected damages for certain return periods and producing parcel-level flood risk profiles. Current FEMA Special Flood Hazard Areas (SFHA), commonly known as the 100-year floodplain, have missed more than a quarter of all National Flood Insurance Program (NFIP) claims since 1978 (Brody, et al., 2013). This highlights the need for improved flood risk estimates which communicate information extending beyond the boundary of the current SFHA. In this work, a risk-based framework is created to produce novel, spatially-based risk profiles by combining hydrologic and hydraulic modeling with damage functions. Due to the spatial nature of these profiles, high risk areas can be targeted with mitigation strategies more directly than before, thereby likely having a greater impact on overall risk reduction. Therefore, risk-based, spatially-targeted mitigation is expected to increase resiliency of urban infrastructure.
Situational Awareness Frameworks for Real-Time Sensing of Flood Impacts on Road Transportation Networks
(2022-12-02) Panakkal, Pranavesh; Padgett, Jamie; Bedient, Philip; Subramanian, Devika; Duenas-Osorio, Leonardo; Mostafavi, Ali
Severe storms and associated flooding pose a significant risk to roadway mobility. Consequently, 40 to 60% of flood-related deaths are attributed to vehicle-related incidents in developed countries. A real-time situational awareness framework that can sense road conditions can facilitate safer mobility, reduce vehicle-related drownings, enhance flood response efficiency, and support emergency response decision-making. Existing situational awareness tools, which often depend on limited data sources and show acceptable performance in limited case studies, fall short of providing a comprehensive framework for sensing flood impacts on roads. Particularly, opportunities to significantly improve situational awareness by leveraging existing data sources in urban regions remain untapped. This thesis addresses this need by offering new tools, models, methodologies, and frameworks for detecting flood impacts on roads in real time and advances the current state-of-the-art for sensing roadway conditions during floods. First, this thesis reports results from semi-structured one-on-one needs assessment interviews with stakeholders responsible for managing flood response in Houston. Specifically, it reports situational awareness data needs for facilitating efficient and safe emergency response, most and least valuable information for situational awareness, communication and visualization strategies, and factors influencing stakeholder trust. These insights inform the methodological underpinning of the three situational awareness frameworks proposed in this thesis. The first situational awareness framework proposed in this thesis senses flood impacts on infrastructure using precompiled maps and real-time rainfall data. The framework offers basic situational awareness information accessible to most communities and is appropriate for areas with limited resources. Relying on precompiled maps to sense real-time flood impacts is often insufficient. This study proposes Open Source Situational Awareness Framework for Mobility (OpenSafe Mobility) to provide a more comprehensive sensing of flood impacts on roads. OpenSafe Mobility uses real-time rainfall data, a physics-based flood model, spatial and network analyses, and vehicle characteristics to sense real-time flood impact on the road transportation system. Case studies using three recent storms in Houston, Texas, demonstrate the framework's ability to provide vehicle-class specific roadway conditions for even minor roads and residential streets—a problem existing approaches struggle with. While OpenSafe Mobility case studies highlight its ability to model flood impacts, it also provides evidence that depending on only one source for sensing flood impacts is insufficient. An alternative is to leverage multiple sources in a data fusion framework to sense current flood conditions. This thesis proposes Open Source Situational Awareness Framework for Mobility using Data Fusion (OpenSafe Fusion) to take advantage of this opportunity. First, OpenSafe Fusion identifies different data sources that either directly or indirectly observe flooding in the study region. Next, source-specific data collection and processing workflows are developed, leveraging diverse techniques from spatial analysis to deep learning. The observations from the sources are then combined in real-time using data fusion techniques explicitly accounting for data source characteristics. Case studies using recent storms in Houston, Texas, demonstrate the framework's ability to significantly improve situational awareness data availability and provide reliable estimates of road conditions using existing public data sources. Finally, this thesis uses OpenSafe Fusion to develop a new prototype web tool for Houston that provide real-time road conditions data for enhancing mobility-centric situational awareness. The proposed tool addresses essential stakeholder needs identified during needs assessment interviews. Overall, this thesis provides new tools, models, methodologies, and frameworks to sense flood impacts on roads in real time and quantify network-level impacts of flooding. Applying the methodologies presented in this thesis will significantly improve situational awareness during flooding. Specifically, it will enable emergency responders and decision-makers to identify flooded roads and safer routes, locate isolated communities, reduce delays and detours, and aid equipment selection. In conclusion, the contributions of this thesis have societal importance in enhancing emergency response efficiency and road safety. These contributions are significant and timely considering the potential increase in flood risk to roadway mobility due to climate change and other factors.
Using a Distributed Hydrologic Model and Unsteady Hydraulic Model on the West Fork San Jacinto River
(2020-07-01) Blaney, Tom Michael; Bedient, Philip
Spatially-distributed hydrologic models and 1D and 2D unsteady hydraulic models have successfully been used to replicate the flows and stages during flood events on creeks and bayous in the Houston area. This study applied these models to the San Jacinto River, a river system with thousands of square miles of drainage area, and hydrologically complex situations such as a dam at Lake Conroe, and the East and West Forks of the river intersecting at Lake Houston. Compared to other watersheds typically modeled in this area, the San Jacinto is much larger and more poorly monitored. A spatially-distributed hydrologic model, Vflo, was used to model patterns of rainfall and runoff in the West Fork San Jacinto River’s drainage area. HEC-RAS 1D unsteady hydraulic models were used to model flood heights along the West Fork, and a HEC-RAS 2D unsteady hydraulic model was used to model flood heights around Lake Houston. These models were able to provide a remarkable replication of the flows and flood heights that occurred during Hurricane Harvey within this river basin, with average NSE values of about 0.9. This study then used a land cover prediction model to estimate land cover in 2050 under various developmental regulations consisting of higher elevation requirements and restrictions on development within wetlands. Only regulations that completely prevented urban development in certain areas were found to affect the amount of development that occurred, reducing the increase in developed area from 63% to 55%. This land use data was then applied to the Vflo and HEC-RAS models, modeling the different peak flows and stages throughout the study area during 10- and 100-year flooding events under the different future land development conditions.

Browsing by Author "Bedient, Philip"

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