scholarly journals STUDY OF THE INUNDATION ANALYSIS OF FLASH FLOODS IN URBAN AREAS FOR RAINFALL IMPACT FORECASTING

2019 ◽  
Author(s):  
SUK HO LEE ◽  
DONG HO KANG ◽  
KYUNG SU CHU ◽  
BYUNG SIK KIM
Keyword(s):  
Urban Areas ◽  
Flash Floods ◽  
Rainfall Impact

scholarly journals The Assessment of Level of Flash Floods Threat of Urbanised Areas

2017 ◽  
Vol 65 (2) ◽  
pp. 519-526 ◽  
Author(s):  
Pavla Štěpánková ◽  
Miroslav Dumbrovský ◽  
Karel Drbal
Keyword(s):  
Czech Republic ◽  
Urban Areas ◽  
Flood Hazard ◽  
Flash Floods ◽  
Flood Risk Assessment ◽  
Entire Area ◽  
The Czech Republic ◽  
Eu Directive ◽  
Run Off ◽  
Technical Measures

Flash floods (or torrential rain flooding) is another type of flood hazard which has caused casualties and significant property damages. A methodology for identification of urban areas, which can potentially be burdened by that type of flood hazard, was proposed. This method, also called Method of Critical Points (CP), is a repeatable process able to identify areas, which are significant in terms of formation of surface run‑off and erosion. As addition to the preliminary flood risk assessment according to EU Directive 2007/60/ES on the Assessment and Management of Flood Risks, the presented methodology was applied for the entire area of the Czech Republic and the results are being used for the updating of non‑technical measures, e.g. urban planning. In the article, the principles of methodology of CP are described and results of the first application in the Czech Republic are presented, as well as possible interpretations of them.

scholarly journals Risk-Based Early Warning System for Pluvial Flash Floods: Approaches and Foundations

Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 127 ◽  
Author(s):  
Julian Hofmann ◽  
Holger Schüttrumpf
Keyword(s):  
Information System ◽  
Early Warning ◽  
Urban Areas ◽  
Heavy Rainfall ◽  
Flood Hazard ◽  
Significant Risk ◽  
Early Warning Systems ◽  
Flash Floods ◽  
Water Levels ◽  
Heavy Rainfall Event

In times of increasing weather extremes and expanding vulnerable cities, a significant risk to civilian security is posed by heavy rainfall induced flash floods. In contrast to river floods, pluvial flash floods can occur anytime, anywhere and vary enormously due to both terrain and climate factors. Current early warning systems (EWS) are based largely on measuring rainfall intensity or monitoring water levels, whereby the real danger due to urban torrential floods is just as insufficiently considered as the vulnerability of the physical infrastructure. For this reason, this article presents a concept for a risk-based EWS as one integral component of a multi-functional pluvial flood information system (MPFIS). Taking both the pluvial flood hazard as well as the damage potential into account, the EWS identifies the urban areas particularly affected by a forecasted heavy rainfall event and issues object-precise warnings in real-time. Further, the MPFIS performs a georeferenced documentation of occurred events as well as a systematic risk analysis, which at the same time forms the foundation of the proposed EWS. Based on a case study in the German city of Aachen and the event of 29 May 2018, the operation principle of the integrated information system is illustrated.

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

2016 ◽  
Vol 11 (3) ◽  
pp. 110-125 ◽  
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.

Modeling of pluvial flash floods in pre-Alpine regions and assessment of potential climate change impacts

2020 ◽  
Author(s):  
Andreas Huber ◽  
Simon Lumassegger ◽  
David Leidinger ◽  
Stefan Achleitner ◽  
Herbert Formayer ◽  
...  
Keyword(s):  
Rural Areas ◽  
Urban Areas ◽  
Climate Change Impacts ◽  
Heavy Precipitation ◽  
Flash Floods ◽  
Climatic Conditions ◽  
Two Dimensional ◽  
Hydrodynamic Models ◽  
General Applicability ◽  
Climate Services

<p>In recent years the topic of flash flooding away from rivers and permanent watercourses has attracted increasing attention from the scientific community, public authorities and affected parts of the general public. Not only urban areas with a high proportion of sealed surfaces, but also rural areas have been adversely affected by pluvial flash floods (PFFs) or surface water floods (SWFs) in the recent past. Empirical evidence suggests that amongst others pre-Alpine areas (e.g. in Austria, Germany, Switzerland, ...) might be especially susceptible to this type of flooding. From a water-management perspective knowledge about potentially endangered areas is important for involved stake-holders as a basis for informed decisions on a variety of topics ranging from protection of existing infrastructure and adaptation of current land use practices to future settlement development. In the light of changing climatic conditions also information on projected future developments is highly desirable. With respect to the latter, an increasing number of datasets from national and pan-European climate-services has become publicly available. Also a growing proportion of two-dimensional hydrodynamic models supports direct rainfall as a boundary condition, thus addressing the special requirements for modeling of PFFs/SWFs.</p><p>We utilize different two-dimensional hydrodynamic models (unstructured-mesh, raster-based) in combination with an event-based hydrological approach to simulate the spatial distribution of surface runoff in response to heavy precipitation events for present conditions and under projected future conditions for small rural areas (< 2km²) in Upper Austria. The general applicability of the used modeling approach is demonstrated. However, also a number of remaining challenges related to the limited quantity and quality of observational data for model calibration and the definition of representative future scenarios is identified and discussed.</p>

scholarly journals Hydrological problems of flash floods and the encroachment of wastewater affecting the urban areas in Greater Cairo, Egypt, using remote sensing and GIS techniques

2020 ◽  
Vol 44 (1) ◽  
Author(s):  
Hanaa A. Megahed ◽  
Mohammed A. El Bastawesy
Keyword(s):  
Remote Sensing ◽  
Urban Areas ◽  
Satellite Images ◽  
Flash Flood ◽  
Flow Direction ◽  
Flash Floods ◽  
Mitigation Measures ◽  
Water Volume ◽  
Gis Techniques ◽  
Greater Cairo

Abstract Background This paper discusses the hydrological problems assessment of flash floods and the encroachment of wastewater in selected urban areas of Greater Cairo using remote sensing and geographic information system (GIS) techniques. The integration of hydrogeological and geomorphological analyses with the fieldwork of drainage basins (Wadi Degla) hosting these urban areas endeavors to provide the optimum mitigation measures that can be feasibly taken to achieve sustainability of the urban areas and water resources available. Results Landsat 5 and Sentinel-2 satellite images were obtained shortly before and after flash flood events and were downloaded and analyzed to define the active channels, urban interference, storage areas, and the natural depressions response. The quantitative flash flood estimates include total GSMap meteorological data sets, parameters of rainfall depths from remote sensing data, active channel area from satellite images, and storage areas that flooded. In GIS, digital elevation model was used to estimate the hydrographic parameters: flow direction within the catchment, flow accumulation, time zone of the catchment, and estimating of the water volume in the largely inundated depressions. Conclusions Based on the results obtained from the study of available satellite images, it has been shown that there are two significant hydrological problems, including the lack of flash flood mitigation measures for urban areas, as the wastewater depressions and sanitary facilities are dotting in the downstream areas.

scholarly journals Identifying urban areas prone to flash floods using GIS – preliminary results

2016 ◽  
Author(s):  
Marzena Wicht ◽  
Katarzyna Osinska-Skotak
Keyword(s):  
Urban Areas ◽  
Drainage System ◽  
Flash Floods ◽  
Temperate Climate ◽  
Hydrological Models ◽  
Preventative Measures ◽  
Radar Measurements ◽  
Gis Environment ◽  
Vegetation Species

Abstract. The aim of this study is to develop a consistent methodology to determine urban areas that are particularly vulnerable to the effects of heavy, rapid rains. They are, as a result of climate change, more and more prevalent in the temperate climate, usually spring – summer from mid-May to late August – and involve the risk of flash floods. In recent years, the increase in incidences of such phenomena is noticeable throughout the whole of Europe. It is assumed that through the analysis of environmental and infrastructural conditions, using the developed methodology, it is possible to determine areas vulnerable to flooding due to torrential rains. This may lead to a better management, quicker response in case of a phenomenon, and even preventative measures to reduce the occurrence of adverse effects of torrential rains (for instance modernisation of the urban drainage system and development of methods to get rid of rapidly collected water). Identifying areas particularly vulnerable to the effects of heavy rains can be achieved by adapting hydrological models, but they require an appropriate adjustment and highly accurate input data: (based in situ or radar measurements of precipitation, land cover, soil type, humidity, wind speed, vegetation species in a given area, growing season, the roughness and porosity of the cover and soil moisture) but such detailed data are generally hard to obtain or not available for less developed areas. It could also be achieved by performing spatial analysis in GIS environment, which is a more simplified form of modelling, but it gives results more quickly and the methodology can be adapted to the commonly available data. The proposed methodology was tested in Warsaw's central sub-district – Powiśle.

scholarly journals Modeling the effects of sediment concentration on the propagation of flash floods in an Andean watershed

2019 ◽  
Author(s):  
María Teresa Contreras ◽  
Cristián Escauriaza
Keyword(s):  
Urban Areas ◽  
Overland Flow ◽  
Mass Conservation ◽  
Sediment Concentration ◽  
Early Warning Systems ◽  
Flash Floods ◽  
Mountain Ranges ◽  
The Andes ◽  
High Concentrations ◽  
Steep Slopes

Abstract. Rain-induced flash floods are common events in regions near mountain ranges. In peri-urban areas near the Andes the combined effects of the changing climate and ENSO have resulted in an alarming proximity of populated areas to flood-prone streams, increasing the risk for cities and infrastructure. Simulations of rapid floods in these watersheds are particularly challenging, due to the complex morphology, the insufficient hydrometeorological data, and the uncertainty posed by the variability of sediment concentration. High concentrations produced by hillslope erosion and rilling by the overland flow in areas with steep slopes and low vegetational covering can change significantly the dynamics of the flow as the flood propagates in the channel. In this investigation, we develop a two-dimensional finite-volume numerical model of the non-linear shallow water equations coupled with the mass conservation of sediment to study the effects of different densities, which include a modified version of the quadratic stress model to quantify the changes on the flow rheology. We carry out simulations to evaluate the effects of the sediment concentration on the floods in the Quebrada de Ramon watershed, a peri-urban Andean basin in central Chile. We simulate a confluence and a total length of the channel of 10.4 km, with the same water hydrographs and different combinations of sediment concentrations in the tributaries. Our results show that the most important effects on the flood propagation are observed in the range of concentrations from 0 % to 20 %. Simulations also show that variables such as the arrival time of the peak flow, and the shape of the hydrograph at different locations along the channel are not significantly affected by the sediment concentration and depend mostly on the steep channel morphology. Through this work we provide a framework for future studies aimed at improving hazard assessment, urban planning, and early warning systems in urban areas near mountain streams with limited data and affected by rapid flood events.

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