Implementation of measures to mitigate the risk of pluvial flooding in urban areas

Towards reproducible pluvial flood simulation in urban areas with TELEMAC-2D

10.5194/egusphere-egu21-5165 ◽

2021 ◽

Author(s):

Tobias Pilz

Keyword(s):

Urban Areas ◽

Extreme Rainfall ◽

Local Information ◽

Flood Simulation ◽

Pluvial Flooding ◽

Severe Flood ◽

Analysis Of Results ◽

Model Setup ◽

Available Information ◽

The City

The megacity of Lagos, Nigeria, is subject to recurrent severe flood events as a consequence of extreme rainfall. In addition, climate change might exacerbate this problem by increasing rainfall intensities. To study the hazard of pluvial flooding in urban areas, several complex hydraulic models exist with a high demand in terms of required input data, manual preprocessing, and computational power. However, for many regions in the world only insufficient local information is available. Moreover, the complexity of model setup prevents reproducible model initialisation and application. This conference contribution addresses these issues by an example application of the complex hydrodynamic model TELEMAC-2D for the city of Lagos. The complex initialisation procedure is simplified by the new package &#8216;telemac&#8217; for the statistical environment R. A workflow will be presented that illustrates the functionality of the package and the use of publicly available information, such as free DEMs and Openstreetmap data to cope with the problem of insufficient local information. By further analysis and visualisation procedures along the workflow the increasing hazard of pluvial flooding for Lagos is shown. The workflow makes model initialisation, application, and the analysis of results reproducible and applicable to other regions with a relatively low need for manual user interventions and without additional software other than R and TELEMAC-2D.

Download Full-text

Towards pluvial flooding hazard assessment in an urban environment

10.5194/egusphere-egu21-11141 ◽

2021 ◽

Author(s):

Omar Seleem ◽

Maik Heistermann ◽

Axel Bronstert

Keyword(s):

Urban Areas ◽

Extreme Rainfall ◽

Likelihood Method ◽

Runoff Generation ◽

Topographic Wetness Index ◽

Extreme Rainfall Events ◽

Flooding Hazard ◽

Pluvial Flooding ◽

Elevation Model ◽

Spatial Window

Urban pluvial floods are considered as a ubiquitous hazard. The increase in intensity and frequency of extreme rainfall events, combined with high population density makes urban areas vulnerable to pluvial flooding. Pluvial floods could occur anywhere depending on the existence of minimal areas for surface runoff generation and concentration. Detailed hydrologic and hydrodynamic simulations are computationally expensive and resource-intensive. This study applies two computationally inexpensive approaches to identify risk areas for pluvial flooding. One approach uses common GIS operations to detect flood-prone depressions from a high-resolution 1m x 1m Digital Elevation Model (DEM), to identify contributing catchments, and to represent runoff concentration by a fill-spill-merge approach. The second approach employs GIS to identify pluvial flood-prone hotspots in terms of the topographic wetness index (TWI).&#160; Based on the exceedance of a TWI threshold, flood-prone areas are identified using a maximum likelihood method. The threshold is estimated by comparing the TWI to inundation profiles from a two-dimensional (2D) hydrodynamic model (TELEMAC 2D), calculated for various rainfall depths within a given spatial window. The two approaches are applied to two flooding hotspots in Berlin, which have been repeatedly subject to pluvial flooding in the last decades and the outputs are compared against the detailed output from TELEMAC 2D.&#160;

Download Full-text

Link between Land Use and Flood Risk Assessment in Urban Areas

Proceedings ◽

10.3390/proceedings2019030062 ◽

2020 ◽

Vol 30 (1) ◽

pp. 62

Author(s):

Zahra Kalantari ◽

Johanna Sörensen

Keyword(s):

Land Use ◽

Land Use Change ◽

Green Infrastructure ◽

Flood Risk ◽

Urban Areas ◽

Land Use Changes ◽

Drainage System ◽

Property Owners ◽

Pluvial Flooding ◽

The Impact

The densification of urban areas has raised concerns over increased pluvial flooding. Flood risk in urban areas might increase under the impact of land use changes. Urbanisation involves the conversion of natural areas to impermeable areas, causing lower infiltration rates and increased runoff. When high-intensity rainfall exceeds the capacity of an urban drainage system, the runoff causes pluvial flooding in low-laying areas. In the present study, a long time series (i.e., 20 years) of geo-referenced flood claims from property owners has been collected and analysed in detail to assess flood risk as it relates to land use changes in urban areas. The flood claim data come from property owners with flood insurance that covers property loss from overland flooding, groundwater intrusion through basement walls, as well as flooding from drainage systems; these data serve as a proxy of flood severity. The spatial relationships between land use change and flood occurrences in different urban areas were analysed. Special emphasis was placed on examining how nature-based solutions and blue-green infrastructure relate to flood risk. The relationships are defined by a statistical method explaining the tendencies whereby land use change affects flood risk.

Download Full-text

Investigating the Effects of Pluvial Flooding and Climate Change on Traffic Flows in Barcelona and Bristol

Sustainability ◽

10.3390/su12062330 ◽

2020 ◽

Vol 12 (6) ◽

pp. 2330 ◽

Cited By ~ 4

Author(s):

Barry Evans ◽

Albert S. Chen ◽

Slobodan Djordjević ◽

James Webber ◽

Andoni González Gómez ◽

...

Keyword(s):

Climate Change ◽

Urban Areas ◽

Future Climate Change ◽

Return Periods ◽

Traffic Flows ◽

Adaptation Measures ◽

Two Cities ◽

Pluvial Flooding ◽

Flooding Events ◽

Business As Usual

This paper outlines the work carried out within the RESCCUE (RESilience to cope with Climate Change in Urban ArEas) project that is, in part, examining the impacts of climate-driven hazards on critical services and infrastructures within cities. In this paper, we examined the methods employed to assess the impacts of pluvial flooding events for varying return periods for present-day (Baseline) and future Climate Change with no adaptation measures applied (Business as Usual) conditions on traffic flows within cities. Two cities were selected, Barcelona and Bristol, with the former using a meso-scale and the latter a micro-scale traffic model. The results show how as the severity of flooding increases the disruption/impacts on traffic flows increase and how the effects of climate change will increase these impacts accordingly.

Download Full-text

Pluvial flooding in urban areas: the role of surface drainage efficiency

Journal of Flood Risk Management ◽

10.1111/jfr3.12246 ◽

2016 ◽

Vol 11 ◽

pp. S663-S676 ◽

Cited By ~ 13

Author(s):

A. Palla ◽

M. Colli ◽

A. Candela ◽

G.T. Aronica ◽

L.G. Lanza

Keyword(s):

Urban Areas ◽

Surface Drainage ◽

Pluvial Flooding

Download Full-text

Socio-Economic Potential Impacts Due to Urban Pluvial Floods in Badalona (Spain) in a Context of Climate Change

Water ◽

10.3390/w11122658 ◽

2019 ◽

Vol 11 (12) ◽

pp. 2658 ◽

Cited By ~ 5

Author(s):

Eduardo Martínez-Gomariz ◽

Luca Locatelli ◽

María Guerrero ◽

Beniamino Russo ◽

Montse Martínez

Keyword(s):

Climate Change ◽

Urban Areas ◽

Rainfall Intensity ◽

Economic Potential ◽

Intergovernmental Panel ◽

Adaptation Measures ◽

Pluvial Flooding ◽

The City ◽

Impacts Of Climate Change

Pluvial flooding in Badalona (Spain) occurs during high rainfall intensity events, which in the future could be more frequent according to the latest report from the Intergovernmental Panel on Climate Change (IPCC). In this context, the present study aims at quantifying the potential impacts of climate change for the city of Badalona. A comprehensive pluvial flood multi risk assessment has been carried out for the entire municipality. The assessment has a twofold target: People safety, based on both pedestrians’ and vehicles’ stability, and impacts on the economic sector in terms of direct damages on properties and vehicles, and indirect damages due to businesses interruption. Risks and damages have also been assessed for the projected future rainfall conditions which enabled the comparison with the current ones, thereby estimating their potential increment. Moreover, the obtained results should be the first step to assess the efficiency of adaptation measures. The novelty of this paper is the integration of a detailed 1D/2D urban drainage model with multiple risk criteria. Although, the proposed methodology was tested for the case study of Badalona (Spain), it can be considered generally applicable to other urban areas affected by pluvial flooding.

Download Full-text

A methodical framework for analysing the cause of urban pluvial flooding in a hillside settlement

Water Science & Technology ◽

10.2166/wst.2019.181 ◽

2019 ◽

Vol 79 (9) ◽

pp. 1798-1807

Author(s):

Lena Simperler ◽

Florian Kretschmer ◽

Thomas Ertl

Keyword(s):

Rural Areas ◽

Urban Areas ◽

Evaluation Criteria ◽

Sewer System ◽

Systematic Analysis ◽

Surface Drainage ◽

Methodical Approach ◽

Pluvial Flooding ◽

Urban And Rural Areas ◽

Urban Pluvial Flooding

Abstract Pluvial flood risk is increasing in urban and rural areas due to changes in precipitation patterns and urbanization. Pluvial flooding is often associated with insufficient capacities of the sewer system or low surface drainage efficiency of urban areas. In hilly areas, hillside runoff additionally affects the risk of pluvial flooding. This article introduces a methodical approach and related evaluation criteria for a systematic analysis of potential causes of urban pluvial flooding. In the presented case study, the cause of pluvial flooding at two selected sites in a hillside settlement is investigated based on a coupled 1D/2D model of the whole hydrological catchment. The results show that even though bottlenecks in the sewer system are important, the effect of low surface drainage efficiency and hillside runoff greatly influence pluvial flooding. The knowledge of different causes of flooding can be further used for selecting and positioning appropriate adaption measures. The presented approach proved its practicability and can thus serve as a guidance and template for other applications to gain better understanding and knowledge of local specific pluvial flooding events.

Download Full-text

A Methodological Approach to Municipal Pluvial Flood Risk Assessment Based on a Small City Case Study

Sustainability ◽

10.3390/su122410487 ◽

2020 ◽

Vol 12 (24) ◽

pp. 10487

Author(s):

Felix Julian Othmer ◽

Dennis Becker ◽

Laura Miriam Schulte ◽

Stefan Greiving

Keyword(s):

Risk Assessment ◽

Flood Risk ◽

Urban Areas ◽

Heavy Rainfall ◽

Methodological Approach ◽

Flood Risk Assessment ◽

Methodical Approach ◽

Pluvial Flooding ◽

Research Procedure ◽

Urban Pluvial Flooding

Urban flooding caused by heavy rainfall confronts cities worldwide with new challenges. Urban flash floods lead to considerable dangers and risks. In cities and urban areas, the vulnerability to pluvial flooding is particularly high. In order to be able to respond to heavy rainfall events with adaptation strategies and measures in the course of urban development, the spatial hazards, vulnerabilities and risks must first be determined and evaluated. This article shows a new, universally applicable methodical approach of a municipal pluvial flood risk assessment for small and medium-sized cities. We follow the common approaches to risk and vulnerability analyses and take into account current research approaches to heavy rainfall and urban pluvial flooding. Based on the intersection of the hazard with the vulnerability, the pluvial flood risk is determined. The aim of the present pluvial flood risk assessment was to identify particularly affected areas in the event of heavy rainfall in the small German city of Olfen. The research procedure and the results have been coordinated with the city’s administration within the framework of a real laboratory. In the course of the science–policy cooperation, it was ensured that the results could be applied appropriately in urban developments.

Download Full-text

Utilising Citizen Science Rain Data for Improved Rainfall Estimation in Urban Pluvial Flooding

10.5194/egusphere-egu21-8734 ◽

2021 ◽

Author(s):

Tess O'Hara ◽

Geoff Parkin ◽

Hayley Fowler ◽

Elizabeth Lewis ◽

Fergus McClean ◽

...

Keyword(s):

Citizen Science ◽

Urban Areas ◽

Monitoring Network ◽

Extreme Rainfall ◽

Rain Gauge ◽

Poor Quality ◽

High Resolution Data ◽

Pluvial Flooding ◽

Weather Stations ◽

Rain Data

Did you know there are millions of rain observations from thousands of privately owned automated weather stations located throughout Britain (and beyond) held in a freely accessible online archive? Citizen Scientists are sharing detailed sub-daily weather observations, including from locations where other gauge data is not available, often in close to real-time. There is distinct clustering of rain gauges in British urban areas, and with an anticipated increase in convective storms resulting in localised pluvial flooding, such high-resolution data should not be ignored. The aims of this research are to assess data quality, investigate how access to the data can be made easier, and to explore how the data can be used to support improved flood risk assessment.British rain observations are presented, spanning 10 years from more than 3000 unique citizen science weather stations via the Met Office WOW archive. These citizen science observations have the potential to fill gaps in the official monitoring network run by the Met Office and agencies responsible for flooding in Britain. Analysis indicates that if the official ground based rain gauge network was interpolated on a 5km grid there would be coverage for 36% of Britain, but if citizen science weather stations were included that figure increases to over 50%. A methodology to identify poor quality observations has been developed; the preliminary findings show that even where absolute values may be inaccurate, citizen science gauges can capture the pattern of extreme rainfall. Examples are shown from work in progress showing how combining citizen science observations with official rain data (radar and ground based gauges) can improve delineation of specific events that resulted in pluvial flooding.

Download Full-text