Advancing Flood Risk Screening

Manycoastal cities are struggling with a rapidly growing risk of flooding. The sizeand complexity of these cities often demand a coordinated strategy, consistingof a combination of flood risk reduction measures. A crucial part in the designprocess is the identification of effective flood risk management strategies. However,data and resources are often limited in these early stages of design, which ischaracterized by the many different options and measures that can be considered.The focus of this study is to identify the needs and challenges of this ‘floodrisk screening’ phase and develop and implement a model framework to supportdecision making in this stage. At the centre of the study is the developmentand application of such a model: the Flood Risk Reduction Evaluation andScreening, or FLORES, model. This dissertation includes two real-life casestudies which explain the structure and development of the FLORES model, aswell as two new applications in conceptual design – flood risk analysis basedon low-resolution data, and robust decision making – that are easier toimplement in flood risk management when combined with flood risk screeningmodels.The FLORESmodel has been implemented in two case studies, one in the USA and one in Mozambique.In the Houston-Galveston Bay Area, USA, the model showed the reliance of theentire region’s flood risk on the choices made at the coastal barriers.Especially the effectiveness of inland Nature-based Solutions heavily relied onthe placement and elevation of coastal structures. In Beira, Mozambique, coastalstructures are combined and compared with other measures, such as drainagesystems, retention, and early-warning systems. The use of flood risk screeningprovided insight into the effectiveness of individual measures, as well ascombinations of measures, and prioritized strategies based on predeterminedgoals. In both cities, these insights, combined with a better understanding ofthe local flood risk and how it is influenced by risk reducing measures andfuture scenarios, can be used to support decision makers in finding the mosteffective strategy going forward.Hydraulic Structures and Flood Ris

Pumped Hydro Storage: Pressure Cavern

The current Dutch electricity market is changing rapidly. New energy agreements demand 40% of Dutch electricity to be produced by renewable sources. This will complicate the link between supply and demand. Where demand used to be the only unknown, also a large part of the electricity supply will become less certain. It is necessary to be able to store energy to keep the Dutch grid stable. Energy Storage This technology is currently very small. The only prosperous technology is that of Pumped Hydro Storage, which uses abundant electricity to pump water into a mountain basin and produces electricity by running this water through a turbine. The requirement of large height differences makes this technology impossible for use in the Netherlands. Pumped Hydro Storage: Pressure Cavern This feasibility study contains the conceptual design of a new energy storage alternative in the Netherlands. It stores water in a low-risk manner by combining the main points of Pumped Hydro Storage with Salt Caverns, which are large cavities left behind by Salt Solution Mining. This form of mining bores into salt domes (large, compressed salt layers) beneath the North-East of the country and leaves large cavities that be used for storage. However, this is impossible to combine with Pumped Hydro Storage, because low pressure will lead to rapid shrinkage of the cavern. The economical competitor There are several parties that will be interested in energy storage, which include energy companies and the National System Operator, TenneT. The yearly revenues are estimated to be 6 million euros. When comparing the market potential a payback period of roughly 8-9 years is expected. The large resemblance to Pumped Hydro Storage limits the risks in comparison to other alternatives. Technical and economic analyses have shown the potential of the Pressure Cavern-concept and conclude that it is definitely a business case worth investigating in order to provide the flexibility that the Dutch market is going to need so badly the coming decades.Hydraulic StructuresHydraulic EngineeringCivil Engineering and Geoscience

Flood risk reduction for Galveston Bay: Preliminary design of a coastal barrier system

Many coastal areas around the world are densely populated and at risk from flooding, but utilize different strategies to deal with coastal hazard. This chapter summarizes how Dutch concepts for coastal flood risk reduction have been explored for Galveston Bay. Firstly, it is shown how risk-based screening methods can help to evaluate various alternative strategies based on metrics such as costs, risk reduction and (societal and environmental) impacts. Application of this approach for Galveston Bay that a coastal spine alternative would entail a large investment, but it would provide the greatest risk reduction by maximizing the protected area. Secondly, a preliminary design for the coastal spine (also known as the Ike Dike) has been elaborated for protection of the region against storm surges, with involvement of Dutch and international students and experts. It includes storm surge barriers at Bolivar Roads and San Luis Pass, and several alternatives for the land barrier—including a fortified dune. Important aspects for future work are discussed, such as the cost estimation, in-bay measures, and the need for integral and proactive planning.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Hydraulic Structures and Flood Ris

Galveston Bay Area: Land Barrier preliminary design

The Galveston Bay Area is under significant risk from hurricane induced flooding. Ever since Hurricane Ike caused billions of damage back in 2008, the option of closing off the Galveston Bay from the Gulf of Mexico was investigated. This report, commissioned by Texas A&M University in Galveston, explores the opportunities and options for the construction of a land barrier across Galveston Island and Bolivar Peninsula. Hydraulic Structures and Flood Ris

Optimization of flood risk reduction through multiple lines of defence

loods can have a huge impact on the regions they affect. The impact of these disasters can be reduced with a flood risk management system. Flood-prone regions often require a combination of interventions to reduce the risk to an acceptable level. The amount of risk reduction provided by various interventions can be quantified using probabilistic risk analysis.Hydraulic Structures and Flood RiskPolicy Analysi

Rapid flood risk screening model for compound flood events in Beira, Mozambique

Coastal cities combine intensive socioeconomic activities and investments with high exposure to flood hazards. Developing effective strategies to manage flood risk in coastal cities is often a costly and complicated process. In designing strategies, engineers rely on computationally demanding flood simulation models, but they can only compare a limited number of strategies due to computational constraints. This limits the efficacy of standard flood simulation models in the crucial conceptual phase of flood risk management. This paper presents the Flood Risk Reduction Evaluation and Screening (FLORES) model, which provides useful risk information in this early conceptual phase. FLORES rapidly performs numerous simulations and compares the impact of many storms, strategies, and future scenarios. This article presents FLORES and demonstrates its merits in a case study for Beira, Mozambique. Our results demonstrate that expansion of the drainage capacity and strengthening of its coastal protection in the southwest are crucial components of any effective flood risk management strategy for Beira.Civil Engineering and GeosciencesHydraulic Structures and Flood RiskPolicy Analysi

The Framework for Integrated Water Management in the Thua Thien-Hue Province

The Thua Thien-Hue province is located in the centre of Vietnam. It is characterized by the short distance between the mountains in the west and the coast of the South China Sea in the east. Two large rivers flow through the province, fed by multiple smaller rivers from the mountains. The Bo River flows through the northern part of the province and ends up in the Cau Hai lagoon. The Huong River is the largest of the two and flows through Hue city ending in the Cau Hai lagoon. The coastal zone of the Thua Thien-Hue province knows a lot of water related problems, like salt intrusion and drought in the dry season and both pluvial and alluvial flooding in the rainy season. Tackling these problems requires an integrated approach that considers all problems, functions and stakeholders. This project will aim to apply a Framework for Integrated Water Management to the Thua Thien-Hue province to minimize the water related problems in the future. This framework assigns different return periods for flooding per area. An area with a high population density will suffer more damage during a flood than a rice paddy, and should have a smaller chance of flooding in order to make the water defence system economically justifiable. This way, a map is created that indicates the desired chance on flooding throughout the coastal, flood prone area of the Thua Thien-Hue province. Using a SOBEK 2D model, the flooding can be simulated. The results from this model show that the amount of water that enters the area is too large to apply traditional protection by raising dikes. Also, most houses are built near the riverbanks, making the implementation of dikes problematic. Two possible solutions were considered. The first, consisting of two bypasses, showed unrealistic as the capacity of the second bypass was insufficient. The second scenario, called “Lake Hue”, uses a reservoir as a retention area during extreme events. A dam regulates the discharge towards Hue City while a spillway towards an area with a lower population density takes care of excess water. An initial cost benefit analysis, using the results from the SOBEK model, indicates a payback time of fifteen years. After the design lifetime of 50 years, the initial investment is returned twofold.Hydraulic EngineeringCivil Engineering and Geoscience

Evaluation of flood risk reduction strategies through combinations of interventions

Large, complex coastal regions often require a combination of interventions to lower the risk of flooding to an acceptable level. In practice, a limited number of strategies are considered and interdependencies between interventions are often simplified. This paper presents the Multiple Lines of Defence Optimization System (MODOS)‐model. This quick, probabilistic model simulates and evaluates the impact of many flood risk reduction strategies while accounting for interdependencies amongst measures. The simulation includes hydraulic calculations, damage calculations, and the effects of measures for various return periods. The application and potential of this model is shown with a conceptual and simplified case study, based on the Houston‐Galveston Bay area. The analyses demonstrate how the MODOS‐model identifies trade‐offs within the system and shows how flood risk, cost, and impact respond to flood management decisions. This improved understanding of the impact of design and planning choices can benefit the discussions in finding the optimal flood risk reduction strategy for coastal regions.Hydraulic Structures and Flood RiskPolicy Analysi