Methodologies to study the surface hydraulic behaviour of urban catchments during storm events

A good knowledge of the hydraulic behaviour of an urban catchment and its surface drainage system is an essential requirement to guarantee traffic and pedestrian safety. In many cases, inlets have been situated according to spatial density criteria. Indeed a more rational location of inlets on urban catchments must be defined according to an accurate analysis of the relationship between street flow and inlet hydraulic efficiency. Moreover we lack specific hazard criteria in terms of the maximum acceptable flow depths and velocities on the streets that do not cause problems to pedestrians. In this paper the results of two different experimental campaigns are presented. The first was carried out to evaluate inlet hydraulic efficiency; the second was carried out to address the pedestrian stability in urban flood conditions, whose aim was to propose new hazard criteria. On the basis of the experimental results, a methodology was developed to assess flood hazard in urban areas during storm events. If a refined topographic representation of urban areas is available, a two-dimensional numerical simulation of urban flooding can be performed using complete shallow water equations. According to this approach a numerical application for flood hazard assessment in a street of Barcelona is shown.

Download Full-text

The Relevance of Grated Inlets within Surface Drainage Systems in the Field of Urban Flood Resilience. A Review of Several Experimental and Numerical Simulation Approaches

Sustainability ◽

10.3390/su13137189 ◽

2021 ◽

Vol 13 (13) ◽

pp. 7189

Author(s):

Beniamino Russo ◽

Manuel Gómez Valentín ◽

Jackson Tellez-Álvarez

Keyword(s):

Overland Flow ◽

Drainage System ◽

Critical Conditions ◽

Hydraulic Efficiency ◽

Storm Events ◽

Urban Resilience ◽

Urban Flood ◽

Drainage Systems ◽

Surface Drainage ◽

Intense Storm

Urban drainage networks should be designed and operated preferably under open channel flow conditions without flux return, backwater, or overflows. In the case of extreme storm events, urban pluvial flooding is generated by the excess of surface runoff that could not be conveyed by pressurized sewer pipes, due to its limited capacity or, many times, due to the poor efficiency of surface drainage systems to collect uncontrolled overland flow. Generally, the hydraulic design of sewer systems is addressed more for underground networks, neglecting the surface drainage system, although inadequate inlet spacings and locations can cause dangerous flooding with relevant socio-economic impacts and the interruption of critical services and urban activities. Several experimental and numerical studies carried out at the Technical University of Catalonia (UPC) and other research institutions demonstrated that the hydraulic efficiency of inlets can be very low under critical conditions (e.g., high circulating overland flow on steep areas). In these cases, the hydraulic efficiency of conventional grated inlets and continuous transverse elements can be around 10–20%. Their hydraulic capacity, expressed in terms of discharge coefficients, shows the same criticism with values quite far from those that are usually used in several project practice phases. The grate clogging phenomenon and more intense storm events produced by climate change could further reduce the inlets’ performance. In this context, in order to improve the flood urban resilience of our cities, the relevance of the hydraulic behavior of surface drainage systems is clear.

Download Full-text

An Exploratory Optimal Framework of Low Impact Development Measures Spatial Arrangement based on Source Tracking for Urban Flood Mitigation

10.21203/rs.3.rs-350792/v1 ◽

2021 ◽

Author(s):

Wenchao Qi ◽

Chao Ma ◽

Hongshi Xu ◽

Zifan Chen ◽

Kai Zhao ◽

...

Keyword(s):

Urban Areas ◽

Flood Hazard ◽

Low Impact Development ◽

Spatial Arrangement ◽

Source Tracking ◽

Urban Flood ◽

Tracking Method ◽

Source Areas ◽

Optimization Framework ◽

Flood Source

Abstract Urban areas are vulnerable to flooding as a result of climate change and population growth and thus rainstorm-induced flood losses are becoming increasingly severe. Low impact development (LID) measures are a storm management technique designed for controlling runoff in urban areas, which is critical for solving urban flood hazard. Therefore, this study developed an exploratory simulation-optimization framework for the spatial arrangement of LID measures. The proposed framework begins by applying a numerical model to simulate hydrological and hydrodynamic processes during a storm event, and the urban flood model coupled with the source tracking method was then used to identify the flood source areas. Next, based on source tracking data, the LID investment in each subcatchment was determined using the inundation volume contribution ratio of the flood source area (where most of the investment is required) to the flood hazard area (where most of the flooding occurs). Finally, the resiliency and sustainability of different LID scenarios were evaluated using several different storm events in order to provide suggestions for flooding predictions and the decision-making process. The results of this study emphasized the importance of flood source control. Furthermore, to quantitatively evaluate the impact of inundation volume transport between subcatchments on the effectiveness of LID measures, a regional relevance index (RI) was proposed to analyze the spatial connectivity between different regions. The simulation-optimization framework was applied to Haikou City, China, wherein the results indicated that LID measures in a spatial arrangement based on the source tracking method are a robust and resilient solution to flood mitigation. This study demonstrates the novelty of combining the source tracking method and highlights the spatial connectivity between flood source areas and flood hazard areas. Further, the framework acts as a strategic tool for the effective spatial arrangement design of LID measures.

Download Full-text

A GIS-BASED PROCEDURE FOR MEASURING THE EFECTS OF THE BUILT ENVIRONMENT ON URBAN FLASH FLOODS

Journal of Green Building ◽

10.3992/jgb.11.3.110.1 ◽

2016 ◽

Vol 11 (3) ◽

pp. 110-125 ◽

Cited By ~ 1

Author(s):

Yan Li ◽

Chunlu Liu

Keyword(s):

Land Use ◽

Built Environment ◽

Urban Areas ◽

Flood Hazard ◽

Land Use Changes ◽

Flash Floods ◽

Flood Inundation ◽

Storm Events ◽

Severe Problem ◽

The Impact

Urban flooding has been a severe problem for many cities around the world as it remains one of the greatest threats to the property and safety of human communities. In Australia, it is seen as the most expensive natural hazard. However, urban areas that are impervious to rainwater have been sharply increasing owing to booming construction activities and rapid urbanisation. The change in the built environment may cause more frequent and longer duration of flooding in floodprone urban regions. Thus, the flood inundation issue associated with the effects of land uses needs to be explored and developed. This research constructs a framework for modelling urban flood inundation. Different rainfall events are then designed for examining the impact on flash floods generated by land-use changes. Measurement is formulated for changes of topographical features over a real time series. Geographic Information System (GIS) technologies are then utilised to visualise the effects of land-use changes on flood inundation under different types of storms. Based on a community-based case study, the results reveal that the built environment leads to varying degrees of aggravation of urban flash floods with different storm events and a few rainwater storage units may slightly mitigate flooding extents under different storm conditions. Hence, it is recommended that the outcomes of this study could be applied to flood assessment measures for urban development and the attained results could be utilised in government planning to raise awareness of flood hazard.

Download Full-text

Ensembles of radar nowcasts and COSMO-DE-EPS for urban flood management

Water Science & Technology ◽

10.2166/wst.2018.079 ◽

2018 ◽

Vol 2017 (1) ◽

pp. 27-35 ◽

Cited By ~ 1

Author(s):

Alrun Jasper-Tönnies ◽

Sandra Hellmers ◽

Thomas Einfalt ◽

Alexander Strehz ◽

Peter Fröhle

Keyword(s):

Urban Areas ◽

Flood Management ◽

Short Term ◽

Ensemble Forecasts ◽

Urban Flood ◽

Rainfall Events ◽

Flood Warning ◽

Urban Catchments ◽

Heavy Rainfall Events

Abstract Sophisticated strategies are required for flood warning in urban areas regarding convective heavy rainfall events. An approach is presented to improve short-term precipitation forecasts by combining ensembles of radar nowcasts with the high-resolution numerical weather predictions COSMO-DE-EPS of the German Weather Service. The combined ensemble forecasts are evaluated and compared to deterministic precipitation forecasts of COSMO-DE. The results show a significantly improved quality of the short-term precipitation forecasts and great potential to improve flood warnings for urban catchments. The combined ensemble forecasts are produced operationally every 5 min. Applications involve the Flood Warning Service Hamburg (WaBiHa) and real-time hydrological simulations with the model KalypsoHydrology.

Download Full-text

Hydraulic Efficiency of Green-Blue Flood Control Scenarios for Vegetated Rivers: 1D and 2D Unsteady Simulations

Water ◽

10.3390/w13192620 ◽

2021 ◽

Vol 13 (19) ◽

pp. 2620

Author(s):

Giuseppe Francesco Cesare Lama ◽

Matteo Rillo Migliorini Giovannini ◽

Alessandro Errico ◽

Sajjad Mirzaei ◽

Roberta Padulano ◽

...

Keyword(s):

Best Management Practices ◽

Urban Areas ◽

Flood Control ◽

Management Practices ◽

Flood Hazard ◽

Control Area ◽

Flood Hazards ◽

Hydraulic Efficiency ◽

Peak Reduction ◽

The Impact

Flood hazard mitigation in urban areas crossed by vegetated flows can be achieved through two distinct approaches, based on structural and eco-friendly solutions, referred to as grey and green–blue engineering scenarios, respectively; this one is often based on best management practices (BMP) and low-impact developments (LID). In this study, the hydraulic efficiency of two green–blue scenarios in reducing flood hazards of an urban area crossed by a vegetated river located in Central Tuscany (Italy), named Morra Creek, were evaluated for a return period of 200 years, by analyzing the flooding outcomes of 1D and 2D unsteady hydraulic simulations. In the first scenario, the impact of a diffuse effect of flood peak reduction along Morra Creek was assessed by considering an overall real-scale growth of common reed beds. In the second scenario, riverine vegetation along Morra Creek was preserved, while flood hazard was mitigated using a single vegetated flood control area. This study demonstrates well the benefits of employing green–blue solutions for reducing flood hazards in vegetated rivers intersecting agro-forestry and urban areas while preserving their riverine ecosystems. It emerged that the first scenario is a valuable alternative to the more impacting second scenario, given the presence of flood control areas.

Download Full-text

Courtyard-level sewer data-enhanced two-dimensional hydraulic model for urban flood hazard assessment in Kunming, China

Water Policy ◽

10.2166/wp.2014.189 ◽

2014 ◽

Vol 17 (1) ◽

pp. 143-161

Author(s):

Zhiqiang Xie ◽

Qingyun Du ◽

Zhongliang Cai ◽

Huaixiang Liu ◽

Sam Jamieson

Keyword(s):

Statistical Method ◽

Urban Areas ◽

Flood Hazard ◽

Ground Surface ◽

Hydraulic Model ◽

Two Dimensional ◽

Urban Flood ◽

One Dimensional ◽

Municipal Level ◽

Overlay Approach

This paper describes a study of urban flooding in downtown Kunming, China, simulating a major flood event that occurred in July 2008 using an improved two-dimensional (2D) hydraulic model enhanced with courtyard-level sewer data (CLSD). Although municipal authorities are not responsible for ‘private’ courtyard sewers, available records were specifically added to this model, enhancing its accuracy and usefulness. Geographic information system (GIS) flood maps, a mapping overlay approach and statistical method compared both predicted results and the recorded flood area. A statistical method also provided a measure of the correlation between the extent of the predicted flood areas and recorded flood areas (parameter ‘F’). Results of the improved 2D/CLSD model showed a correlation value for F of 51, 32.6% higher than the basic one-dimensional municipal-level sewer data (1D/MLSD) model; 26.2% higher than an interim version of the model that included a 2D ground surface (2D/MLSD). The 2D/CLSD model predicted flooding in 10 of the 12 courtyards with observed flooding. This was a major improvement over the 1D/MLSD model (three out of 12) and the 2D/MLSD model (five out of 12). Thus a CLSD-enhanced 2D hydraulic model potentially improves accuracy in predicting, mapping and understanding flood risk in urban areas.

Download Full-text

Assessment of Community Vulnerability to Different Types of Urban Floods: A Case for Lishui City, China

Sustainability ◽

10.3390/su12197865 ◽

2020 ◽

Vol 12 (19) ◽

pp. 7865 ◽

Cited By ~ 1

Author(s):

Quntao Yang ◽

Shuliang Zhang ◽

Qiang Dai ◽

Rui Yao

Keyword(s):

Urban Areas ◽

Flood Hazard ◽

Urban Flooding ◽

Urban Floods ◽

Flood Vulnerability ◽

Urban Flood ◽

Indicator Method ◽

Comprehensive Method ◽

Different Types ◽

Hydrometeorological Conditions

Urban flooding is a severe and pervasive hazard caused by climate change, urbanization, and limitations of municipal drainage systems. Cities face risks from different types of floods, depending on various geographical, environmental, and hydrometeorological conditions. In response to the growing threat of urban flooding, a better understanding of urban flood vulnerability is needed. In this study, a comprehensive method was developed to evaluate the vulnerability of different types of urban floods. First, a coupled urban flood model was built to obtain the extent of influence of various flood scenarios caused by rainfall and river levee overtopping. Second, an assessment framework for urban flood vulnerability based on an indicator method was used to evaluate the vulnerability in different flood hazard scenarios. Finally, the method was applied to Lishui City, China, and the distribution and pattern of urban flood vulnerability were studied. The results highlight the spatial variability of flooding and the vulnerability distributions of different types of urban floods. Compound floods were identified to cause more severe effects in the urban areas.

Download Full-text

Using High-Density LiDAR Data and 2D Streamflow Hydraulic Modeling to Improve Urban Flood Hazard Maps: A HEC-RAS Multi-Scenario Approach

Water ◽

10.3390/w11091832 ◽

2019 ◽

Vol 11 (9) ◽

pp. 1832 ◽

Cited By ~ 13

Author(s):

Alin Mihu-Pintilie ◽

Cătălin Ioan Cîmpianu ◽

Cristian Constantin Stoleriu ◽

Martín Núñez Pérez ◽

Larisa Elena Paveluc

Keyword(s):

Urban Areas ◽

Large Scale ◽

Flood Hazard ◽

Hydraulic Modeling ◽

Flood Mitigation ◽

Small Scale ◽

Lidar Data ◽

Hazard Maps ◽

Urban Flood ◽

Flood Hazard Maps

The ability to extract streamflow hydraulic settings using geoinformatic techniques, especially in high populated territories like urban and peri-urban areas, is an important aspect of any disaster management plan and flood mitigation effort. 1D and 2D hydraulic models, generated based on DEMs with high accuracy (e.g., Light Detection and Ranging (LiDAR)) and processed in geographic information systems (GIS) modeling software (e.g., HEC-RAS), can improve urban flood hazard maps. In this study, we present a small-scale conceptual approach using HEC-RAS multi-scenario methodology based on remote sensing (RS), LiDAR data, and 2D hydraulic modeling for the urban and peri-urban area of Bacău City (Bistriţa River, NE Romania). In order to test the flood mitigation capacity of Bacău 1 reservoir (rB1) and Bacău 2 reservoir (rB2), four 2D streamflow hydraulic scenarios (s1–s4) based on average discharge and calculated discharge (s1–s4) data for rB1 spillway gate (Sw1) and for its hydro-power plant (H-pp) were computed. Compared with the large-scale flood hazard data provided by regional authorities, the 2D HEC-RAS multi-scenario provided a more realistic perspective about the possible flood threats in the study area and has shown to be a valuable asset in the improvement process of the official flood hazard maps.

Download Full-text

Improving Urban Flood Mapping by Merging Synthetic Aperture Radar-Derived Flood Footprints with Flood Hazard Maps

Water ◽

10.3390/w13111577 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1577

Author(s):

David C. Mason ◽

John Bevington ◽

Sarah L. Dance ◽

Beatriz Revilla-Romero ◽

Richard Smith ◽

...

Keyword(s):

Synthetic Aperture Radar ◽

Real Time ◽

Rural Areas ◽

Urban Areas ◽

Flood Hazard ◽

Synthetic Aperture ◽

Hazard Maps ◽

Urban Flood ◽

Flood Hazard Maps ◽

Aperture Radar

Remotely sensed flood extents obtained in near real-time can be used for emergency flood incident management and as observations for assimilation into flood forecasting models. High-resolution synthetic aperture radar (SAR) sensors have the potential to detect flood extents in urban areas through clouds during both day- and night-time. This paper considers a method for detecting flooding in urban areas by merging near real-time SAR flood extents with model-derived flood hazard maps. This allows a two-way symbiosis, whereby currently available SAR urban flood extent improves future model flood predictions, while flood hazard maps obtained after the SAR overpasses improve the SAR estimate of urban flood extents. The method estimates urban flooding using SAR backscatter only in rural areas adjacent to urban ones. It was compared to an existing method using SAR returns in both rural and urban areas. The method using SAR solely in rural areas gave an average flood detection accuracy of 94% and a false positive rate of 9% in the urban areas and was more accurate than the existing method.

Download Full-text

Role of physical settings on increasing flood hazard in Muscat Built-up areas (2007-2015) using GIS

Journal of Arts and Social Sciences [JASS] ◽

10.24200/jass.vol9iss1pp65-78 ◽

2018 ◽

Vol 9 (1) ◽

pp. 65

Author(s):

Rana N. Jawarneh ◽

Said S. Almushaiki

Keyword(s):

Urban Area ◽

Urban Areas ◽

Flood Hazard ◽

Hazard Map ◽

Urban Flood ◽

Flooding Hazard ◽

Environmental Attributes ◽

Flood Hazard Map ◽

Hazard Zone ◽

High Flood

This study aims at evaluating selected environmental attributes of urban development pathways in relation to their impacts on increasing cyclone-related flooding in the Governorate of Muscat for the years 2007, 2010, 2013, and 2015. A probability-weighted flood hazard map for the 2015 urban areas was produced by combining all selected environmental attributes into one probability equation, with each attribute given a weight. The 2015 urban flood hazard map showed that 31.7 km² (8.1% of total urban areas) of the built up area is located in the very high flooding hazard zone, 88.3 km² (22.6% of urban area) is located in the high flood hazard zone, 130.5 km² (33.5% of urban area) is located in the medium flooding hazard zone, and 113.4 km² (29.1% of urban area) and 26.1 km² (6.7% of urban area) located in the low and very low flooding hazard zones. The outputs from this research emphasize the potential of environmental forces to increase flood damages. The findings provide decision makers with spatially-explicit evidences on affected areas for more effective evacuation and rescue plans.

Download Full-text