Adaptation Strategies for Flooding Risk from Rainfall Events in Southeast Spain: Case Studies from the Bajo Segura, Alicante

The management of runoff during torrential rainfall events is a significant problem in urban areas of southeast Spain. The increase in soil sealing and the occupation of areas prone to flooding have aggravated this problem. Due to this situation, municipal administrations, in collaboration with the concession holder for the supply of water and sewage services, Hidraqua Gestión Integral de Aguas de Levante SA, are committed a more efficient management of non-conventional water resources. An example of this can be found in the municipalities of Rojales, Daya Nueva, and San Fulgencio. These towns are located in the Bajo Segura region of the province of Alicante, where various initiatives have been implemented that break away from the traditional paradigm of rigid infrastructures. These initiatives include green spaces or areas, and sustainable urban drainage systems (SUDS) or nature-based solutions (NBS). This article presents various case studies. Firstly, in the town of Rojales, where several actions are being undertaken to improve the management of wastewater and rainwater and provide a solution to unauthorised dumping, as well as encouraging the use of reclaimed water with the creation of a recreational green area, El Recorral Park. Secondly, in the case of Daya Nueva, the Europa Park constitutes a recreational green area, Europa Park, facilitates runoff drainage by SUDS and NBS. Finally, the creation of a floodable pond in the municipality of San Fulgencio encourages the use of wastewater, thus avoiding the discharge of this non-conventional water resource into the sea. In addition, the pond facilitates the appropriate management of runoff water. The working method in this article has been twofold: firstly, bibliographical references have been consulted from other national and international areas; and secondly, the technical projects in the case studies have been analysed in detail. Several field trips have been made to the selected municipalities, accompanied by the technical personnel in charge of the execution of the projects, to examine the measures adopted. The results show that the implementation of these systems contributes to adapting to climate change and creates more resilient urban spaces.

Strengthen resilience to rivers flooding by the drag reduction technique

Urban agglomerations face the risk of overflowing rivers due to intense urbanization in flood-prone areas and the climate change effects. Despite the important protective measures deployed to reduce the fluvial flooding risk, additional efforts are still needed. This work aims to propose a new complementary non-structural protection measure, used to reduce the river flooding risk. The study is part of the NABRAPOL (NEBRASKA POLYMER) project, which aims to improve knowledge of the drag reduction effect by adding polymers in open-channel flows. The addition of polymers, even in limited concentrations, allows high friction to decrease with the typical Manning coefficient reduced up to 45%. An application case on a real watercourse is presented in this article. Two measurement campaigns are carried out on a river along 30 km. Experimental devices are deployed, and non-intrusive hydraulic measuring instruments are installed at the study field. Surface velocities are evaluated by the Large-Scale Particle Image Velocimetry (LSPIV) technique, and water depth is measured using ultrasonic radar sensors over the river. Measurement results show that the addition of 20 ppm of polymers in the flows results in a marked drag reduction by decreasing the water depth to 18% of its initial depth. The drag reduction technique by addition of small concentrations of polymers can be considered as a new and effective method to reinforce the measures already deployed in the flood risk management strategy since it allows the water depth to be decreased thus avoid overflowing rivers in the extreme flooding event.

A hybrid risk assessment approach for assessing the earthquake risks in worn-out urban fabrics: a case study in Iran

Purpose To reduce financial and human losses, managing risks associated with earthquakes is essential in practice. However, in using common risk management methods, experts are often faced with ambiguities that can create profound challenges for risk management. Therefore, it is necessary to develop a logical and straightforward risk assessment model to provide scientific and accurate answers to complex problems. This study aims to recommend an innovative combined method based on the probability-impact (P-I) approach and intuitionistic fuzzy set theory to identify and prioritize the essential earthquake risks associated with worn-out urban fabrics in the context of Iran. Design/methodology/approach The opinions of 15 experts in the fields of civil engineering and urban construction were gathered during brainstorming sessions. These brainstorming sessions were conducted to determine the probability of risks and the effect of identified risks. After calculating the severity of risks using the P-I approach and converting them to intuitionistic fuzzy sets, the risks were measured and prioritized based on their individual scores. Findings The study results indicated that risk of damage due to buildings’ age and flooding risk had the highest and lowest priorities in causes of financial damage, respectively. Furthermore, the risk of damage due to building quality (demolition) and building age was the most important. The risk of flooding and damage to communication networks has the lowest importance among causes of fatalities in worn-out urban fabrics. Originality/value The study findings and recommendations can be served as a policy and consultative instrument for the relevant stakeholders in the area of urban management.

Hybrid Approach for Excess Stormwater Management: Combining Decentralized and Centralized Strategies for the Enhancement of Urban Flooding Resilience

Urban sprawl and soil sealing has gradually led to an impervious surface increase with consequences on the enhancement of flooding risk. During the last decades, a hybrid approach involving both traditional storm water detention tanks (SWDTs) and low-impact development (LID) has resulted in the best solution to manage urban flooding and to improve city resilience. This research aimed at a modeling comparison between drainage scenarios involving the mentioned hybrid approach (H-SM), with (de)centralized LID supporting SWDTs, and a scenario representative of the centralized approach only involving SWDTs (C-SM). Results highlighted that the implementation of H-SM approaches could be a great opportunity to reduce SWDTs volumes. However, the performances varied according to the typology of implemented LID, their parameterization with specific reference to the draining time, and the rainfall severity. Overall, with the increase of rainfall severity and the decrease of draining time, a decrease of retention performances can be observed with SWDTs volume reductions moving from 100% to 28%. In addition, without expecting to implement multicriteria techniques, a preliminary cost analysis pointed out that the larger investment effort of the (de)centralized LID could be, in specific cases, overtaken by the cost advantages resulting from the reduction of the SWDTs volumes.

Urban Flooding Risk Assessment Based on Numerical Simulation of Sub-catchment Area: A Case Study From Chengdu, China

Urbanization and climate change usually result in frequent urban flooding. Since the floods cannot be avoided, the scenario simulation combined with risk analysis is an effective way to assess the disaster level and reduce direct damage loss when facing the emergency management problems. Different from the whole city dimension, the paper proposed a sub-catchment multi-index hesitant fuzzy evaluation model for the community planning level, and takes Jinjiang District of Chengdu city as the research object. Firstly, based on the PSR (Pressure-State-Response) model, the risk assessment system has been established in three aspects, including the current situation of urban drainage, the basic geographic information, and the social influence. Secondly, A total of 14 evaluation indexes were selected, among which the pressure index came from the calculation results of ArcGIS and EPASWMM5 model such as runoff coefficient, maximum water depth, etc. Thirdly, the expert hesitate fuzzy evaluation method was used to obtain the weight of 14 indexes of each sub-catchment. Finally, the 224 evaluation results were compared, and the urban flooding disaster risk map has been drawn. It is mainly concluded that 160 medium-higher risk areas were mainly concentrated in high built-up area in study area. Furthermore, the evaluation model is very useful as a decision-making tool for mitigation of the flood hazard and its associated risk.

Assessment of Exposure to Flash Flooding in an Arid Environment: A Case Study of the Jeddah City Neighborhood Abruq Ar Rughamah, Saudi Arabia

In arid areas, flash floods represent one of the most severe hazards for people and infrastructure alike. The associated risks are compounded by increasing exposure and vulnerability through rapid and unregulated urbanization, poor infrastructure, and sociocultural factors, among other elements. This research explores the flash flooding risk in the Saudi Arabian city of Jeddah with a particular focus on the Abruq Ar Rughamah neighborhood, which experienced a destructive flood in November 2009 that resulted in 116 deaths and 1,200 families becoming homeless. The neighborhood is an interesting case study as it has two distinctive urban layouts representing planned and irregular settlement types. In this paper, the focus is placed on exposure to flash flood hazards using a geographic information system to study urban layouts, building types, and resident populations in conjunction with data from satellites, flood mapping studies, and topographic data. The results show that most of the study area is located along a natural flood path. The regions that were affected by the 2009 disaster received no comprehensive site rehabilitation. This paper concludes that it is important to develop a risk management strategy that includes limiting urban expansion in flood-prone areas and redesigning neighborhoods to increase flood resilience.

Topo-bathymetric and oceanographic datasets for coastal flooding risk assessment: French Flooding Prevention Action Program of Saint-Malo

The French Flooding Prevention Action Program of Saint-Malo requires assessment of coastal flooding risks. The first prerequisite is a knowledge of the topography and bathymetry of the bay of Saint-Malo. In addition to existing topo-bathymetric data, the acquisition of new multibeam bathymetric data is performed. The combination of these datasets allows the generation of two high resolution topo-bathymetric digital terrain models. Then, to understand the hydrodynamic conditions which cause coastal flooding, a dense and extensive oceanographic field experiment is conducted. Oceanographic data were acquired using a network of 22 moorings with 37 sensors, during winter 2018–2019. The network included 2 directional buoys, 2 pressure tide gauges, 18 wave pressure gauges, 4 single-point current meters, 7 current profilers and 4 acoustic wave-current profilers from mid-depth (25 m) up to the upper beach and the dike system. The oceanographic dataset provides an overview of hydrodynamics in Saint-Malo bay and wave processes leading to coastal flooding. The combination of high-resolution topo-bathymetric and oceanographic datasets provides a unique capability for model validation and process studies. The topo-bathymetric and oceanographic datasets are available freely at doi : https://doi.org/10.17183/MNT_COTIER_GNB_PAPI_SM_20m_WGS84, https://doi.org/10.17183/MNT_COTIER_PORT_SM_PAPI_SM_5m_WGS84, and https://doi.org/10.17183/CAMPAGNE_OCEANO_STMALO.

River Flood Modelling For Flooding Risk Mitigation in Iraq

River flood events have recently been increased due to many reasons such as climate change and excessive land usage. Thus, one of the greatest challenges is to control the flooding in urban areas. River flooding has become a phenomenon worldwide in general and in Iraq specifically. This is associated with the rapid increase of urbanization as well as mismanagement of land utilization; especially those located near the river banks, in addition to lack of consideration in terms of the design and implementation of drainage networks. In Iraq and especially in Al-Anbar governorate, studies in the field of flood simulation control have been rare. This study aims to suggest a fast and accurate methodology for local authorities, by providing a proposed solution and prediction of flooding area in the case study of the Fallujah barrage. Global Mapper software has been used to produce simulation photos on flooding area. Earth Explorer USGS website has been used to download water body data; and Global Digital Surface website has been used to extract and download the surface elevation data. The result of the simulation photos has predicted valuable information about the flooding area and proposed a general vision on the areas that are under threat of flooding. Four main areas were exposed to flooding, area 1, area 2, area 3, and area 4; A total flooding area of 11.89 km2. The total maximum operational level for the barrage was designed to be 44.79 m above sea level. Also, the recommended maximum operation level for the barrage was 43 m ASL. Doi: 10.28991/cej-2021-03091754 Full Text: PDF