Thesis (M.S.)--University of Delaware, 2007. / Principal faculty advisors: Jack B. Gingrich and Charles E. Mason, Dept. of Entomology & Wildlife Ecology. Includes bibliographical references.

A l'occasion de ce travail de thèse, nous avons souhaité contribuer aux études d'impacts du changement climatique sur le bilan d'eau en Europe. Nous avons utilisé les outils de la modélisation du climat, modèle de circulation générale et schéma de surface, et nous nous sommes placés à l'interface entre l'atmosphère et la surface. Ce travail s'est décomposé en deux parties. Dans un premier temps, nous avons étudié la sensibilité du bilan d'eau simulé par le schéma de surface du laboratoire, ORCHIDEE, à la résolution des forçages atmosphériques sur deux régions d'Europe, la péninsule ibérique et le bassin versant du Rhône (dans le cadre du projet international Rhône-AGG). Dans un deuxième temps, nous avons abordé la thématique des impacts du changement climatique sur le bilan d'eau sous un angle plus atmosphérique, par l'étude des dépressions qui traversent l'Atlantique en direction de l'Europe, et de leurs liens avec les précipitations.

Runoff from road construction and maintenance sites is responsible for erosion and deposition of sediments in the receiving water bodies. In addition to soil particles from erosion, runoff also transports other pollutants such as rubber, toxic metals, automobile fluids, car exhausts (which settle with the rain), pesticides, fertilizers, and other debris. Compost has been used effectively as a valuable soil amendment to aid plant growth. Berms (mounds) of compost placed at the top or bottom of steep slopes can be used to slow the velocity of water and provide additional protection for receiving waters. However, a downside of the application of composted organic material is the potential degradation of runoff water quality. Overloading with nitrogen and phosphorus causes eutrophication, which reduces the suitability of waterways for beneficial uses. A field testing of the berms coupled with a laboratory analysis of the testing water will provide a basis for the impact of the compost berms on the runoff water quality. The study of the impact of compost on the runoff water quality was investigated. The objective of this study was to evaluate the performance of berms made from various materials such as dairy manure compost, yard waste compost and composted bio-solids mixed with wood chips in a ratio of 50:50 on the runoff water quality, as well as, the sediment removal efficiencies. Field tests were performed on the berms to simulate conventional rainfall runoff and the tested water was collected as time-weighted samples and analyzed in the laboratory. Several variables were investigated during this study. Results of this investigation demonstrated that the effectiveness of this application was hampered by the structural instability of the berm. A 100% failure rate was observed in the berms tested. Optimum performance was observed in yard waste compost berms, which introduced the least amount of contaminants into the water. However, some masking effect could be present due to berm failures. In fact, the actual sediment removal by the berms could not be determined. The study of compost filter berms showed some evidence of the existence of first flush effect.

More frequent and harsh storms coupled with sea level rise are affecting Canada’s sensitive coastlines. This research studies Isle Madame in Cape Breton, Nova Scotia which has been designated by Natural Resource Canada as a sea level rise vulnerable coastal community in Canada. The research models the spatial and temporal impacts of sea level rise from storm surge by focusing on identifying vulnerable areas in the community via geographical information systems (GIS) using ArcGIS, as well as modeling dynamic coastal damage via system dynamics using STELLA. The research evaluates the impacts in terms of the environmental, social, cultural, economic pillars that profile the coastal community for a series of modelled Storm Scenarios. This research synthesizes information from a variety of sources including the coastal ecology and natural resources, as well as human society and socioeconomic indicators included in the four mentioned pillars. The objective of the research is to determine vulnerable areas on Isle Madame susceptible to storm damage, and consequently, to improve local community knowledge and preparedness to more frequent harsh storms. This research therefore presents a dynamic model for the evaluation of storm impacts in Isle Madame designed with the goal to help the community ultimately to plan and implement a strategy to adapt to pending environmental change.

Hurricanes are one of the primary threats to the Texas coastal environment and economy. They generate large wave and storm surges that have caused much damage on the Texas coast in the past. Understanding both the hydrodynamic processes that damage coastal habitats and hurricane hazard and risk are critical to preserve coastal vegetation and quantify its benefits to coastal storm protection. The goal of this project is to quantify the impact of wave attenuation and wave refraction as well as the development of coherent structures in marsh fringes and the formation of a rip current system over wetlands on storm protection. The 3D Shallow Water Wave Basin at Texas A&M University hosted a series of large-scale experiments considering an idealized wetland model to pursue this goal. Study of the marsh geometry of the Texas coast was done in order to scale the experiments to the size of the Haynes Laboratory 3D-Water Wave Basin using a Froude and a Reynolds scalings. Particularly, averaged size and idealized shape of marsh segments in the area of Dalehite Cove in Galveston Bay were considered. Three sets of different wave conditions and water levels were tested to approximate different intensities of storm surge. Identical tests with both vegetated and non-vegetated marshes were run to compare the influence of the vegetation in storm conditions, and three different spacings between marsh segments were tested. In the basin, normally incident regular waves were generated at three water circulation structures. Data analysis allows the determination of the impact of discontinuous marsh segments on wave attenuation and wave refraction. Coherent structures such as rip current and the circulation pattern were analyzed to study the change in the flow field during passage of the waves. The experimental measurements were able to describe the wave transformations over the marsh segments. The influence of coastal wetlands was identified to affect the hydrodynamic process and reduce the total wave energy which is dissipated and redistributed by vegetation. The presence of the mounds induced an important decrease in the wave height, in addition to the damping of the waves by the vegetation stems. The variation in spatial coverage of the wetland model has been shown to highly affect the flow dynamics by generating offshore directed flow in the channel and onshore directed flow on the marsh mounds. This experimental approach provides a further understanding of flow dynamics by waves and surge in wetlands, at a large scale.

More frequent and harsh storms coupled with sea level rise are affecting Canada’s sensitive coastlines. This research studies Isle Madame in Cape Breton, Nova Scotia which has been designated by Natural Resource Canada as a sea level rise vulnerable coastal community in Canada. The research models the spatial and temporal impacts of sea level rise from storm surge by focusing on identifying vulnerable areas in the community via geographical information systems (GIS) using ArcGIS, as well as modeling dynamic coastal damage via system dynamics using STELLA. The research evaluates the impacts in terms of the environmental, social, cultural, economic pillars that profile the coastal community for a series of modelled Storm Scenarios. This research synthesizes information from a variety of sources including the coastal ecology and natural resources, as well as human society and socioeconomic indicators included in the four mentioned pillars. The objective of the research is to determine vulnerable areas on Isle Madame susceptible to storm damage, and consequently, to improve local community knowledge and preparedness to more frequent harsh storms. This research therefore presents a dynamic model for the evaluation of storm impacts in Isle Madame designed with the goal to help the community ultimately to plan and implement a strategy to adapt to pending environmental change.

This study presents an unsteady-state hydraulic model analysis of hurricane storm surge and rainfall-runoff interactions in the Clear Creek Watershed, a basin draining into Galveston Bay and vulnerable to flooding from both intense local rainfalls and storm surge. Storm surge and rainfall-runoff have historically been modeled separately, and thus the linkage and interactions between the two during a hurricane are not completely understood. This study simulates the two processes simultaneously by using storm surge stage hydrographs as boundary conditions in the Hydrologic Engineering Center’s – River Analysis System (HEC-RAS) hydraulic model. Storm surge hydrographs for a severe hurricane were generated in the Advanced Circulation Model for Oceanic, Coastal, and Estuarine Waters (ADCIRC) model to predict the flooding that could be caused by a worst-case scenario. Using this scenario, zones have been identified to represent areas in the Clear Creek Watershed vulnerable to flooding from storm surge, rainfall, or both.

During the nineties, ecological handling of urban storm water became very popular in Sweden. Together with Chalmers University of Technology and two Swedish communities, DHI Water and Environment has been doing research of storm water ponds and constructed wetlands. This thesis work is a part of that research project. The work has been applied at the Bäckaslöv storm water treatment plant in Växjö, Sweden. The plant consists of one storm water pond and a downstream constructed wetland. Simulations in two different modelling programs, MIKE SHE WET and MIKE 21 have been performed. MIKE SHE WET has never been used in practical work. The purpose of the program is to describe chemical and biological processes in wetlands and how the plants affect the retention of nutrients in the water. Since the program never has been used before, the main work has been to test the model to investigate whether it fulfil its purpose or not. MIKE 21 has been used to describe how the geometry influences the retention of suspended material, nitrogen and phosphorus. MIKE 21 has also been used to study how the wetland works without the storm water pond. To be able to describe the natural processes going on in wetlands the program MIKE SHE WET has to be further developed. The work has yet resulted in a package of measures that can improve the model. Science is in need for a model like MIKE SHE WET. If the program will be edited it can contribute a lot to the research of wetlands and storm water treatment. The simulations in MIKE 21 show that today’s shape of the wetland is not most favourable. If the water was spread over a bigger area the retention of nitrogen, phosphorus and suspended material would increase. / Anläggandet av konstgjorda våtmarker och sedimenteringsdammar har varit intensivt under nittiotalet och ekologisk dagvattenhantering har blivit mycket populärt i Sveriges kommuner. DHI Water and Environment bedriver i samarbete med Chalmers tekniska Högskola samt Växjö och Örebro kommuner ett forskningsprojekt kring anlagda dammar och våtmarker. Meningen är att resultaten ska kunna användas vid såväl uppföljningsarbete av befintliga dammar samt vid anläggandet av nya dagvattenanläggningar. Detta examensarbete ingår som en del av ovan nämnda forskningsprojekt. Arbetet har tillämpats på Bäckaslövs dagvattenanläggning i Växjö. Anläggningen består av en sedimenteringsdamm med efterföljande våtmark. Modellstudier har utförts i två olika modellprogram, MIKE SHE WET och MIKE 21. MIKE SHE WET har inte tidigare använts i praktiken och har därför testats för att undersöka om programmet uppfyller sitt syfte. Programmet har utformats för att kunna simulera växternas påverkan på kväve- och fosforretentionen. Med hjälp av MIKE 21 har simuleringar utförts för att undersöka hur våtmarkens geometri kan förändras för att få en optimerad avskiljning av kväve, fosfor och suspenderat material. Simuleringar har också utförts för att undersöka hur våtmarken skulle fungera utan uppströms liggande sedimenteringsdamm. Resultaten visar på att MIKE SHE WET måste vidareutvecklas för att kunna beskriva de biologiska och kemiska processer som pågår i våtmarken. Arbetet har lett fram till ett antal konkreta åtgärdsförslag för att förbättra programmet och modellen har potential att bli ett viktigt hjälpmedel i framtida forskning kring våtmarker. MIKE 21-simuleringarna har visat mycket goda resultat. Resultaten visar på att våtmarken idag inte har optimal utformning för att kunna rena det dagvatten som flödar in i den. Om våtmarken utformas så att vattnet får en större spridning i området kommer reningen av såväl suspenderat material som kväve och fosfor att förbättras.

During the onslaught of a storm on the coasts of Taiwan in summer and autumn, large waves and storm surge have often caused beach erosion. In order to mitigate coastal disasters and erosion, soft-options have been promoted in recent years, to fulfill the purpose of shore protection, as well as to meet the new requirements of landscape, ecology and recreation. Consequently, semi-natural approaches have been adopted in stead of the conventional hard-structures. This thesis aims to report a study on the effects of detached submerged breakwater layouts and storm wave types on beach profile changes and berm retreat. In order to establish a practical procedure to assist the assessment of beach profile changes with submerged breakwaters during storm, we first collect and analyze the beach profile change data performed in large wave tanks (CE from the US and PI from Japan), and apply the well known SBEACH model to derive regression relationship between the two key parameters ( and ) in this model against the non-dimensional fall velocity ( ). The suggestion of Larson and Kraus (2000) to include hard bottom option in SBEACH with a set of modified and values, which may be different from that originally developed for a sandy beach environment, is then carried out using the beach profile changes results conducted experimentally with submerged breakwaters (Risio and Lisi, 2010). Consequently, we have conducted the numerical experiments systematically to study the beach profile changes using submerged breakwaters under various environmental combinations (with 10 different offshore distances, 10 breakwater heights, 10 crown widths and 4 types of storm wave conditions derived from storm return periods), from which a new set of and values are derived and used in SBEACH for the investigation of installing submerged breakwaters to mitigate potential beach erosion. Our numerical investigations using SBEACH for a beach with submerged breakwater reveal that: (1) Beach profile changes in erosion (0 m line and berm) and accretion (0 m line) due to regular waves are more significant than that of irregular waves. (2) Storm waves with a long return period cause more erosion to the shoreline (0 m line) and berm, while that with short return period may produce accretion to the shoreline. (3) The further a submerged breakwater away offshore, the more sediment transportation offshore and severe beach and berm erosion. (4).An increase of submerged breakwater height would result in accretion near the 0 line; except during a violent storm event, when an increase of berm height could reduce berm erosion. (5) An increase to the crown width of a submerged breakwater could only become effective to reduce wave energy and berm erosion, if an appropriate breakwater height is used; otherwise, a mere increase in width with insufficient height would increase wave height and berm erosion.

Given the past history and future risk of storm surge in the United States, alternative storm protection techniques are needed to protect vital sectors of the economy and population, particularly within southeastern Louisiana. It is widely hypothesized that coastal wetlands offer protection from storm surge and wave action, though the extent of this protection is unknown due to the complex physics behind vegetated flow dynamics. This thesis presents numerical modeling results that estimate the relative sensitivity of waves and storm surge to characteristics embodied by coastal wetlands. An idealized grid domain and 400 km2 (20 km by 20 km) marsh feature provide a controlled environment for evaluating marsh characteristics, including bottom friction, elevation, and continuity. Marsh continuity is defined as the ratio of healthy marsh area to open water area within the total wetland area. It is determined that increased bottom friction reduces storm surge levels and wave heights. Through the roughening of the bottom from sandy to covered with tall grass, it is estimated that waves may be dampened by up to 1.2 m at the coast, and peak surge may be reduced by as much as 35%. The lowering of marsh elevation generally increases wave heights and decreases surge levels, as expected. A 3.5 m decrease in marsh elevation results in as much as a 2.6 m increase in wave height, and up to a 15% decrease in surge levels. Reductions in marsh continuity enhance surge conveyance into and out of the marsh. For storms of low surge potential, surge is increased by as much as 70% at the coast due to decreasing marsh continuity from 100% to 50%, while for storms of high surge potential, surge is decreased by 5%. This indicates that for storms of high surge potential, a segmented marsh may offer comparable surge protection to that of a continuous marsh. Wave heights are generally increased within the marsh due to the transmission of wave energy through marsh channels. Results presented in this thesis may assist in the justification of coastal wetland mitigation, and optimize marsh restoration in terms of providing maximum storm protection.