Flood Mitigation Systems Research Articles

Key drivers of vulnerability to rainfall flooding in New Orleans

IntroductionFuture urban stormwater flood risk is determined by the confluence of both climate-driven changes in precipitation patterns and the effectiveness of flood mitigation systems, such as urban drainage and pump systems. This is especially true in coastal cities protected by levee systems like New Orleans, where even present-day rainfall would be enough to cause serious flooding in the absence of extensive stormwater drainage and pumping. However, while the uncertainties associated with climate change have been well studied, uncertainties in infrastructure performance and operation have received less attention.MethodsWe investigated how these interrelated sets of uncertainties drive flood risk in New Orleans using a Robust Decision Making (RDM) approach. RDM is a framework for Decision Making Under Deep Uncertainty (DMDU) that leverages simulation models to facilitate exploration across many possible futures and the identification of decision-relevant scenarios. For our work, we leveraged a detailed Storm Water Management Model (SWMM) representation of the New Orleans urban stormwater management system to examine flood depths across the city when faced with different levels of future precipitation, sea-level rise, drainage pipe obstruction, and pumping system failure. We also estimated direct flood damage for each neighborhood in the city for this scenario ensemble. These damage estimates were then subjected to vulnerability analysis using scenario discovery—a technique designed to determine which combinations of uncertainties are most stressful to the system in terms of an outcome of interest (excess flood damage).ResultsOur results suggest that key drivers of vulnerability depend on geographic scale. Specifically, we find that possible climate-driven precipitation increases are the most important determinant of vulnerability at the citywide level. However, for some individual neighborhoods, infrastructure operation challenges under present day conditions are a more significant driver of vulnerability than possible climate-driven precipitation increases.

Rainfall Intensity-Duration-Frequency Relationships: A Robust Foundation for Urban Decision-Making and Flood Management: A Case Study

Ahmedabad, a city in India, experiences varying climatic patterns and is prone to extreme rainfall and relies on established intensity-duration-frequency (IDF) relationships for critical infrastructure planning and flood management. While the city has existing IDF relationships, these curves were established some time ago and still lack well-established IDF Curves. To fill this research gap this study is dedicated to the development of IDF curves for Ahmedabad City, utilizing 45 years of rainfall data (1978 to 2022) sourced from the Indian Meteorological Department (IMD) making our study a pioneering effort in this direction. Employing frequency analysis methodologies, the relationships between rainfall intensity, storm duration, and return periods were established. IDF curves were generated for durations of 5, 10, 15, 30 minutes, and 1, 2, 6, 12 and 24 hours for Ahmedabad City. Short-term rainfall intensities were derived from daily rainfall values using the IMD formula. The empirical approach, Gumbel distribution, and Log Pearson Type-III distribution were applied. The Gumbel method tends to produce slightly higher rainfall intensities for shorter return periods, while the LPT III method exhibits the opposite pattern for longer return periods, such as 25, 50, and 100 years. In general, both approaches yield closely matching results across most return periods. The IDF curves produced in this study offer a versatile set of rainfall scenarios for diverse applications, including the design and modification of hydraulic structures, stormwater management infrastructure, and flood mitigation systems in Ahmedabad City. The outcomes of this research contribute not only to filling a crucial research gap but also empower decision-makers and urban planners with updated and reliable data crucial for enhancing the city’s resilience against extreme rainfall events.

Flood Discharge For Ungauged Catchment At Teriang River, Pahang By Using HEC-HMS

Insufficiency of meteorological data during extreme rainfall events hinders simulation and forecasting analysis in flood mitigation systems. Hence, the existence of a reliable database in hydrology is crucial in flood modelling for ungauged catchments, especially for calibration and validation purposes. This paper focused on the generation of rainfall data by using Hydrological Procedure No. 1 (HP1) from the Department of Irrigation and Drainage (DID) Malaysia. Subsequently, analysis of flood hydrographs at Teriang River, Pahang, Malaysia, using HEC-HMS 4.8 for 50 and 100-year return periods was also obtained in this study. For validation purposes, the outcomes were compared to Hydrological Procedure No. 11 (HP11), designed for rural catchments. For precipitation data generation, the design rainfall was calculated based on generalised isopleth maps from HP1 for various rainfall durations ranging from 0.25 hours to 72 hours. Based on the results, the maximum peak discharge for 50 ARI was 354.7 m3/s, while for 100 ARI it was 410 m3/s before calibration. Comparing the results from the HEC-HMS model and the outputs from HP11, the analysis for 50-year and 100-year return periods in the Teriang River showed that the relative percentage differences for peak discharge were 19.99% and 17.64%, respectively. The calibration process managed to obtain a relative percentage difference of 2.94% for 50 ARI and 4.36% for 100 ARI. In conclusion, HEC-HMS can be used as a reliable tool to produce simulated streamflow for ungauged catchments with the help of the generated rainfall temporal patterns from HP1, which is a procedure that contains estimation of design rainfall intensity based on the rainfall intensity-during-frequency relationship (IDF relationship).

Robust optimisation of combined rainwater harvesting and flood mitigation systems

Combined large-scale rainwater harvesting (RWH) and flood mitigation systems are promising as a sustainable water management strategy in urban areas. These are multi-purpose infrastructure that not only provide a secondary, localised water resource, but can also reduce discharge and hence loads on any downstream wastewater networks if these are integrated into the wider water network. However, the performance of these systems is dependent on the specific design used for its local catchment which can vary significantly between different implementations. A multitude of design strategies exist, however there is no universally accepted standard framework. To tackle these issues, this paper presents a two-player optimisation framework which utilises a stochastic design optimisation model and a competing, high-intensity rainfall design model to optimise passively-operated RWH systems. A customisable tool set is provided, under which optimisation models specific to a given catchment can be built quickly. This reduces the barriers to implementing computationally complex sizing strategies and encouraging more resource-efficient systems to be built. The framework was applied to a densely populated high-rise residential estate, eliminating overflow events from historical rainfall. The optimised configuration resulted in a 32% increase in harvested water yield, but its ability to meet irrigation demands was limited by the operational levels of the treatment pump. Hence, with the inclusion of operational levels in the optimisation model, the framework can provide an efficient large-scale RWH system that is capable of simultaneously meeting water demands and reducing stresses within and beyond its local catchment.

Feasibility of Traditional Open Levee System for River Flood Mitigation in Japan

An open levee system is a traditional flood mitigation system for reducing the expansion of inland flooding and decreasing the peak flow. However, there have been few quantitative studies on its feasibility. Furthermore, the differences in applicability depending on the topography and the construction of continuous levees have not been fully examined. We studied its feasibility based on simulations in the Kuji River area, where the vast Typhoon Hagibis occurred. Morphological models representing the past (the 1940s) and the present (2019), obtained by modifying the highly accurate digital elevation models (DEM) via the tracing of aerial photos, were applied to a 2D unsteady flow simulation model to reveal the effects of the levee system on river hydrography and overland flood behavior. The results indicated that inundation flow through an open area decreased both inundation duration and depth, while the reduction of peak discharge is relatively insignificant at approximately 10%. The sub levees are not adequate under the current conditions and floodwater volume, and their effectiveness depends on the surrounding conditions, such as the development of continuous levees.

Development of Water Supply and Drainage Automation Equipment for Paddy Fields and Application to Flood Mitigation Systems

Paddy rice agriculture is one of the main industries in the Asahikawa region. Due to the shortage of successors, reducing the workload of the elderly is an urgent issue. As one of these measures, there is a need for a device that automates the water supply and drainage of rice fields. Most of the devices currently being developed are not widespread because the cost of the entire system is high or the type of water supply and drainage is performed by an underdrain method. Therefore, in our laboratory, we are developing a device that can supply and drain water directly from a general open-ditch irrigation canal. The feature of this device is that it is automated by using an electric cylinder for the opening and closing mechanism of the floodgate and using the wedge gate method for sealing the floodgate. In addition, one of the factors that cause the flood to increase in scale is drainage from rice fields during heavy rains, and we are studying ways to apply this device to flood mitigation systems.

Urban Flood Risk and Economic Viability Analyses of a Smart Sustainable Drainage System

Urban drainage systems are in transition from functioning simply as a transport system to becoming an important element of urban flood protection measures providing considerable influence on urban infrastructure sustainability. Rapid urbanization combined with the implications of climate change is one of the major emerging challenges. The increased concerns with water security and the ageing of existing drainage infrastructure are new challenges in improving urban water management. This study carried out in the Seixal area in Portugal examines flood risk analyses and mitigation techniques performed by computational modelling using MIKE SHE from the Danish Hydraulic Institute (DHI). Several scenarios were compared regarding flood risk and sustainable urban drainage systems (SuDS) efficiency. To obtain a more accurate analysis, the economic viability of each technique was analyzed as well through (i) life cost analysis and (ii) taking into account the damages caused by a certain type of flood. The results present that the best scenario is the one that will minimize the effects of great urbanization and consequently the flood risk, which combines two different measures: permeable pavement and detention basin. This alternative allows us to fully explore the mitigation capacity of each viable technique, demonstrating a very important improvement in the flood mitigation system in Seixal.

Evaluating pluvial flood hazard for highly urbanised cities: a case study of the Pearl River Delta Region in China

Rapid urbanisation and economic growth in developing Asian countries have exacerbated their exposure to flood hazards, particularly evident in low-lying urban cities that are currently facing increasing risks from extreme precipitations, likely made worse by the impending climate change. We present a set of simplified indices representative of the characteristics of rainfall-run-off process for evaluating pluvial flood hazard using the fuzzy comprehensive evaluation method. The highly urbanised Pearl River Delta (PRD) region in southern China is studied as an example of mapping the regional pluvial flood hazard and assessing the socio-economic exposure at risk. The developed hazard map captures the broad patterns of high flood hazard zones when compared with reported surface water flooding hotspots and the PRD riverine flood map from the 2015 Global Assessment Report. Further analysis on the regional socio-economic profiles suggests that most PRD cities are faced with large flood loss potential, with estimates of approximate 23 million people and 2.4 trillion RMB gross domestic product exposed to high flood hazard. Mega cities Guangzhou and Shenzhen top the ranking with over 20–40% of their dense urban settlements in the high flood hazard zone. This highlights the impact of human activities on the natural surface run-off process, and the need for robust flood hazard assessment for better understanding and design of holistic solutions towards more adequate flood mitigation systems for continuous urbanisation and future climate conditions.

An Analysis of Preparedness and The Impact of Floods in India

India is the most flood prone country in the world with instances of at least 15 major occurrences in the last decade. Apart from loss of lives and property, the country suffers huge economic, infrastructural as well as environmental damage on a yearly basis. In addition, several indirect and prolonged effects of floods affect the country as well. This is coupled with facilitating factors such as global warming and unplanned development in flood plains. Understanding the gravity of the situation, the government of India enacted the Disaster Management Act in 2005 subsequently forming the National Disaster Management Authority. This body has developed guidelines for flood mitigation at national, state as well as at regional levels. The country needs to develop effective flood mitigation system in order to reduce the periodic damage endured by the people and the state.

A Surrogate-Based Optimization Design and Uncertainty Analysis for Urban Flood Mitigation

This study proposes a surrogate-based optimization framework (SBO) to help analyze the tradeoff between flood damages and investment while considering uncertainty originating from surrogates. The surrogate models were constructed based on the relationship between drainage specifications and simulated flood information and used to replace the numerical model in optimization, thereby reducing the computational burden. The bootstrapping approach was employed to quantify the uncertainty originating from surrogate models, which were incorporated into the NSGA-II optimization algorithm to seek the interval of optimal solutions. Through a case study, the results showed that the uncertainties caused by surrogate models have a significant influence on the reliability of the optimal solutions, but require lower computational efforts. Moreover, the local design conditions (i.e., various designed rainfalls) had an impact on the design and performance of the detention tanks. The proposed framework will facilitate cost-effective planning of flood mitigation systems with an awareness of associated uncertainty in order to resolve tradeoffs, particularly for large-scale problems.

Efficient forecasting model technique for river stream flow in tropical environment

ABSTRACTMonthly stream flow forecasting can provide crucial information on hydrological applications including water resource management and flood mitigation systems. In this statistical study, time series and artificial intelligence methods were evaluated according to implementation of each time-series technique to find an effective tool for stream flow prediction in flood forecasting. This paper explores the application of water level, rainfall data and input time series into three different models; linear regression (LR), auto-regressive integrated moving average (ARIMA) and artificial neural networks (ANN). The performances of the models were compared based on the maximum coefficient of determination (R2) and minimum root means square error (RMSE). Based on the results the ANN model presents the most accurate measurement, with the R2 value of 0.868 and 18% RMSE. The present study suggests that ANN is the best model due to its ability to recognise times series patterns and to understand non-linear relationships.

A Super Region Approach to Improve Pooled Flood Frequency Analysis

Floods are known as one of the most damaging natural hazards with devastating influence on people and the environment. Accurately estimating flood frequencies is essential for effective design of flood mitigation systems. Estimation of these frequencies is difficult since extreme events are rare and the length of recorded data is often short. In such situations, extreme flow information from a number of similar sites is combined (pooled) to augment the available at-site information. Pooled flood frequency analysis is a well-known approach used to improve the estimation of extreme flow quantiles at sites with short data records. Identification of pooling groups that will effectively transfer extreme flow information is thus essential. The present paper proposes an approach to improve flood quantile estimates through utilizing the concept of super regions integrated with seasonality-based similarity measures to conduct pooled frequency analysis for extreme flow events. To identify homogeneous regions, this study focuses on the region of influence (ROI), or focussed pooling group approach among hydrological neighborhood techniques. To define the hydrologically similar neighborhood of a target site, a single numeric that measures similarity/dissimilarity between sites is usually utilized. This work investigates the effect of employing catchment physiographic-climate characteristics and several flood seasonality statistics as the similarity measures. Moreover, this study explores and establishes a super region technique that in a hierarchical process employs the two types of similarity measures. A large dataset of catchments across Canada was used to compare the proposed method with more traditional approaches. The effectiveness of these techniques both in terms of constructing homogeneous pooling groups and accurately estimating extreme flow quantiles is explored for the catchments under study. The proposed super region approach was shown to form more reliable homogeneous pooling groups. Analyzing confidence intervals of quantile estimates obtained from pooled and at-site estimates revealed promising improvement.

Flood hazard mitigation in land subsidence prone coastal areas by optimal groundwater pumping

Continuing land subsidence can aggravate flood hazard and diminish the effectiveness of existing flood mitigation systems. This paper presents a study of groundwater‐ pumping management for mitigating flood hazard in a subsidence infested area in the southwest coast of Taiwan. An optimal groundwater‐pumping model is developed for preventing flood hazard from worsening and for satisfying the groundwater demand. In an area where the land is susceptible to pumping‐induced subsidence, the study shows that proper long‐term pumping strategy to manage spatial–temporal variation of future land subsidence should be an integral part of flood risk management as it can sustain the effectiveness of the flood mitigation measures.

Impact of urbanization on flood of Shigu creek in Dongguan city

Abstract. Shigu creek is a highly urbanized small watershed in Dongguan City. Due to rapid urbanization, quick flood response has been observed, which posted great threat to the flood security of Dongguan City. To evaluate the impact of urbanization on the flood changes of Shigu creek is very important for the flood mitigation of Shigu creek, which will provide insight for flood planners and managers for if to build a larger flood mitigation system. In this paper, the Land cover/use changes of Shigu creek from 1987–2015 induced by urbanization was first extracted from a local database, then, the Liuxihe model, a physically based distributed hydrological model, is employed to simulate the flood processes impacted by urbanization. Precipitation of 3 storms was used for flood processes simulation. The results show that the runoff coefficient and peak flow have increased sharply.

Evaluation of the wind pumped hydropower storage integrated flood mitigation system

As Wind Pumped Hydropower Storage (WPHS) need high cost to construct, it is important to study their impacts on economic and environmental aspects. Thus, this research aims to evaluate their economic and environmental performances. First, Hybrid Optimization Model for Electric Renewable (HOMER) was used to simulate power generation system with and without the flood reservoir. Next, the total amount of emitted air pollutant was used to evaluate the environmental impacts. It was found the wind-diesel with reservoir storage system (A-III) will have much lower NPC than other systems that do not include reservoir for flood mitigation when the cost of flood losses are included in the total Net Present Cost (NPC). The NPC for system A-III was RM 1.52 million and for diesel standalone system (A-I) is RM 10.8 million when the cost of flood losses are included in the total NPC. Between both energy systems, the amount of pollutants emitted by the A-III system was only 408 kg-CO2/year which is much less than the A-I system which is 99, 754 kg of carbon dioxide per year. To conclude, the WPHS integrated with flood mitigation system seems promising in the aspects of economic and environment.

Drag coefficient for amphibious house

Recently, flooding has become a serious issue and disaster in Malaysia. Therefore, it is crucial to search for a more effective flood mitigation approach in Malaysia. Amphibious house system is a new sustainable and flexible flood mitigation measure within a floating urbanization environment. Amphibious house has been designed based on buoyancy terminology by using precast and fast formulatable concrete components such as concrete pontoons. These pontoons are made of green lightweight concrete and analysed for buoyancy and stability against vertical and horizontal loads. This study aims to identify the precise force calculation from floods to amphibious houses as a new flood mitigation system. The objective of this study is to develop a new equation for calculating the drag coefficient for the amphibious house. A new experimental method is used to calculate drag force on the amphibious house in 1/25 scaled-down floodplain model. As a result, the new equation is developed for the drag coefficient. The sensitivity analysis shows the accuracy of this research.

A framework model for the dimensioning and allocation of a detention basin system: The case of a flood-prone mountainous watershed

Summary A straightforward approach in flood management is the attenuation of peak discharges through an appropriate detention system. In this study, a flexible framework model was developed to optimize the dimensioning and site selection of a flood mitigation system based on detention basins. The general workflow can be summarized by three separate but interrelated modules: ( i ) the hydrologic module, which back tracks the detention basin contributing area based on the application of engineering formulae to historical information on local river floods and associated hydrometric data; ( ii ) the geomorphologic module, implemented in a Geographic Information System, which indicates all the potential locations with adequate contributing area as required for the detention system, by analyzing the flow accumulation within the river basin; and ( iii ) the environmental module, which comprises the implementation of a multi-criteria decision analysis for the selection of best location(s) for the detention basin system, addressing three different objectives: to minimize diffuse pollution; to minimize point-source pollution; to optimize landscape integration (by minimizing the dam height). The framework model was applied to the flood-prone Vez River, which is the main tributary of the Lima River in Northwestern Portugal. Although the expectations as regards diffuse and point-source pollution are optimistic, results show that detention of the largest flood in this river could only be accomplished with one very large dam or a number of decentralized large dams. Decentralizing the detention system with multiple basins installed in various branches of the Vez River did not reduce the mean dam height, because the catchment is located in a region of craggy topography and high annual rainfall. An extensive reforestation of the basin headwaters would increase evapotranspiration reducing runoff. Eventually, this would expand the alternatives for flood mitigation, namely through the construction of sustainable flood detention basins.

On comparison of peak flow reductions, flood inundation maps, and velocity maps in evaluating effects of restored wetlands on channel flooding

With growing interest in using restored and/or new constructed wetlands as additional flood mitigation systems, it has become essential to investigate the effectiveness of wetlands in reducing the risk of flood hazards. This study examines and compares evaluation techniques based on peak flow estimation, flood inundation area estimation, and velocity maps to assess the performance of wetlands in reducing flood hazards in a Midwestern watershed affected by changing precipitation patterns. School Branch, one of the main branches of Eagle Creek watershed, located in central Indiana, was selected as a study area. A coupled hydrologic-hydraulic model approach was proposed to simulate the outflow generated by various design storms. Then the water profile and water velocity in the river were calculated and finally the inundation and velocity maps were generated. Also, the effect timing of storm on runoff modulated by wetlands was investigated by applying design storms to different months of year. The results of this study show that wetlands can reduce the peak flow up to 42%, flood areas up to 55% and maximum velocity up to 15%. Additionally, a sub-basin that had maximum peak flow reduction for a specific design storm did not necessarily have a simultaneous maximum reduction in flood inundation area, indicating the variability in how wetlands mitigate flooding in different sub-basins of a watershed. Also, deeper wetlands are more effective in reducing the impacts of storms with higher return periods. For example, at the study site, deeper wetlands (D=1.8m) were able to reduce peak flows up to 20% for a 500 year storm whereas shallow wetlands (D=0.5m) reduced the peak flow by 11% for the same storm.

Tropical Storm Allison Recovery: A Facilities And Operations Perspective

The Texas Medical Center was devastated by Tropical Storm Allison on June 8th and 9th, 2001 resulting in diminished operational services for several key healthcare facilities in the Houston community. Memorial Hermann Hospital and Memorial Hermann Children\'s Hospital experienced severe flooding to two lower levels of the facility and the resultant loss of key utility systems necessitated a systematic evacuation of the patient population. The Hermann facility was closed to patient care for a period of 38 days while operational systems were restored and the facility re-certified for health-care operations. Key to the disaster was the unprecedented storm event (estimated at a frequency greater than a 100-year event) (1), changes in watershed development patterns, and the location of key utility systems below-grade in many facilities. Master planning efforts are currently in progress to add system redundancies, improve preparedness for future utility interruptions, install flood mitigation systems, and relocate key systems/functions to areas with reduced risk of future flooding.