scholarly journals Safer_RAIN: A DEM-Based Hierarchical Filling-&-Spilling Algorithm for Pluvial Flood Hazard Assessment and Mapping across Large Urban Areas

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1514 ◽  
Author(s):  
Caterina Samela ◽  
Simone Persiano ◽  
Stefano Bagli ◽  
Valerio Luzzi ◽  
Paolo Mazzoli ◽  
...  
Keyword(s):  
Urban Areas ◽  
Flood Hazard ◽  
Urban Environments ◽  
Extreme Precipitation Events ◽  
Digital Elevation ◽  
Pluvial Flooding ◽  
Spatially Distributed ◽  
Fast Processing ◽  
Urban Settlements ◽  
Precipitation Events

The increase in frequency and intensity of extreme precipitation events caused by the changing climate (e.g., cloudbursts, rainstorms, heavy rainfall, hail, heavy snow), combined with the high population density and concentration of assets, makes urban areas particularly vulnerable to pluvial flooding. Hence, assessing their vulnerability under current and future climate scenarios is of paramount importance. Detailed hydrologic-hydraulic numerical modeling is resource intensive and therefore scarcely suitable for performing consistent hazard assessments across large urban settlements. Given the steadily increasing availability of LiDAR (Light Detection And Ranging) high-resolution DEMs (Digital Elevation Models), several studies highlighted the potential of fast-processing DEM-based methods, such as the Hierarchical Filling-&-Spilling or Puddle-to-Puddle Dynamic Filling-&-Spilling Algorithms (abbreviated herein as HFSAs). We develop a fast-processing HFSA, named Safer_RAIN, that enables mapping of pluvial flooding in large urban areas by accounting for spatially distributed rainfall input and infiltration processes through a pixel-based Green-Ampt model. We present the first applications of the algorithm to two case studies in Northern Italy. Safer_RAIN output is compared against ground evidence and detailed output from a two-dimensional (2D) hydrologic and hydraulic numerical model (overall index of agreement between Safer_RAIN and 2D benchmark model: sensitivity and specificity up to 71% and 99%, respectively), highlighting potential and limitations of the proposed algorithm for identifying pluvial flood-hazard hotspots across large urban environments.

Pluvial flooding in urban areas: Parsimonious hazard mapping for a case study in Berlin, Germany

2020 ◽  
Author(s):  
Omar Seleem ◽  
Maik Heistermann ◽  
Axel Bronstert
Keyword(s):  
Urban Areas ◽  
Flood Hazard ◽  
Computational Cost ◽  
Hazard Mapping ◽  
Urban Landscapes ◽  
Runoff Generation ◽  
Flow Paths ◽  
Digital Elevation ◽  
Pluvial Flooding

<p>Urban pluvial floods are increasingly recognized as a ubiquitous hazard. They are caused by short and intense rainfall, followed by rapid runoff concentration. But while flood hazard maps for rivers have been widely implemented under the EU Flood Directive, corresponding efforts for pluvial flooding are rare, yet: pluvial floods are not to the existence of a river channel. They could occur anywhere, subject to the existence of minimal areas for surface runoff generation and concentration. That concentration could be dominated by small features of urban landscapes, which makes identification of flow paths uncertain even with highly-resolved digital elevation models (DEM) and full hydrodynamic simulations (which are computationally expensive). At the same time, sub-surface sewer and drainage systems – an additional complication in an already complex environment – will typically be subject to overcharge for extremely heavy rainfall events. That, however, allows us to focus on the surface in order to assess the hazard from such events. In the present study, we present a low-(computational)-cost approach to identify areas at risk of pluvial flooding. Common GIS operations are used to detect flood-prone depressions from a high-resolution 1m x 1m DEM, identify contributing watersheds, and represent runoff concentration by a fill-spill-merge approach. The approach is applied to a study area in Berlin, which has been repeatedly subject to pluvial flooding in the past years.</p>

scholarly journals Safer_RAIN: a Fast-Processing DEM-Based Algorithm for Pluvial Flood Hazard Assessment Across Large Urban Areas

2019 ◽  
Author(s):  
Attilio Castellarin ◽  
Caterina Samela ◽  
Simone Persiano ◽  
Stefano Bagli ◽  
Valerio Luzzi ◽  
...  
Keyword(s):  
Hazard Assessment ◽  
Urban Areas ◽  
Flood Hazard ◽  
Flood Hazard Assessment ◽  
Fast Processing

Analysing urban floods and combined sewer overflows in a changing climate

2011 ◽  
Vol 2 (4) ◽  
pp. 260-271 ◽  
Author(s):  
V. Nilsen ◽  
J. A. Lier ◽  
J. T. Bjerkholt ◽  
O. G. Lindholm
Keyword(s):  
Climate Change ◽  
Time Series ◽  
Urban Areas ◽  
Convective Precipitation ◽  
Urban Drainage ◽  
Combined Sewer Overflows ◽  
Extreme Precipitation Events ◽  
Combined Sewer ◽  
Sewer Overflows ◽  
Precipitation Events

Climate change is expected to lead to an increased frequency and intensity of extreme precipitation events. For urban drainage, the primary adverse effects are more frequent and severe sewer overloading and flooding in urban areas, and higher discharges through combined sewer overflows (CSO). For assessing the possible effects of climate change, urban drainage models are run with climate-change-adjusted input data. However, current climate models are run on a spatial–temporal scale that is too coarse to resolve processes relevant to urban drainage modelling, in particular convective precipitation events. In the work reported here the delta-change method was used to develop a high-resolution time series of precipitation for the period 2071–2100 based on a recently produced climate model precipitation time series for Oslo. The present and future performance of the sewer networks was determined using MOUSE software. The simulations indicated future increases in annual CSO discharge of 33% when comparing years of maximum annual runoff. There is also an 83% increase in annual CSO discharge when comparing years of maximum annual precipitation. In addition, there are increases in the flooding of manholes and increased levels of backwater in pipes, which translates into more flooding of basements.

scholarly journals Building Extraction from Very High Resolution Stereo Satellite Images Using OBIA and Topographic Information

2020 ◽  
Vol 5 (1) ◽  
pp. 1
Author(s):  
Minakshi Kumar ◽  
Ashutosh Bhardwaj
Keyword(s):  
High Resolution ◽  
Urban Areas ◽  
Large Scale ◽  
Decision Rules ◽  
Urban Environments ◽  
Fuzzy Rules ◽  
Building Extraction ◽  
Digital Elevation ◽  
Elevation Model ◽  
Very High

The availability of very high resolution (VHR) satellite imagery (<1 m) has opened new vistas in large-scale mapping and information management in urban environments. Buildings are the most essential dynamic incremental factor in the urban environment, and hence their extraction is the most challenging activity. Extracting the urban features, particularly buildings using traditional pixel-based classification approaches as a function of spectral tonal value, produces relatively less accurate results for these VHR Imageries. The present study demonstrates building extraction using Pleiades panchromatic (PAN) and multispectral stereo satellite datasets of highly planned and dense urban areas in parts of Chandigarh, India. The stereo datasets were processed in a photogrammetric environment to obtain the digital elevation model (DEM) and corresponding orthoimages. DEM’s were generated at 0.5 m and 2.0 m from stereo PAN and multispectral datasets, respectively. The orthoimages thus generated were segmented using object-based image analysis (OBIA) tools. The object primitives such as scale parameter, shape, textural parameters, and DEM derivatives were used for segmentation and subsequently to determine threshold values for building fuzzy rules for building extraction and classification. The rule-based classification was carried out with defined decision rules based on object primitives and fuzzy rules. Two different methods were utilized for the performance evaluation of the proposed automatic building approach. Overall accuracy, correctness, and completeness were evaluated for extracted buildings. It was observed that overall accuracy was higher (>93%) in areas having larger buildings and that were sparsely built-up as compared to areas having smaller buildings and being densely built-up.

scholarly journals Efficient Hazard Assessment for Pluvial Floods in Urban Environments: A Benchmarking Case Study for the City of Berlin, Germany

Water ◽  
2021 ◽  
Vol 13 (18) ◽  
pp. 2476
Author(s):  
Omar Seleem ◽  
Maik Heistermann ◽  
Axel Bronstert
Keyword(s):  
Surface Runoff ◽  
Urban Areas ◽  
Model Performance ◽  
Urban Environments ◽  
Likelihood Method ◽  
Runoff Generation ◽  
Topographic Wetness Index ◽  
Inundation Maps ◽  
Pluvial Flooding ◽  
Storm Drainage

The presence of impermeable surfaces in urban areas hinders natural drainage and directs the surface runoff to storm drainage systems with finite capacity, which makes these areas prone to pluvial flooding. The occurrence of pluvial flooding depends on the existence of minimal areas for surface runoff generation and concentration. Detailed hydrologic and hydrodynamic simulations are computationally expensive and require intensive resources. This study compared and evaluated the performance of two simplified methods to identify urban pluvial flood-prone areas, namely the fill–spill–merge (FSM) method and the topographic wetness index (TWI) method and used the TELEMAC-2D hydrodynamic numerical model for benchmarking and validation. The FSM method uses common GIS operations to identify flood-prone depressions from a high-resolution digital elevation model (DEM). The TWI method employs the maximum likelihood method (MLE) to probabilistically calibrate a TWI threshold (τ) based on the inundation maps from a 2D hydrodynamic model for a given spatial window (W) within the urban area. We found that the FSM method clearly outperforms the TWI method both conceptually and effectively in terms of model performance.

Building Resilience After Climate-Related Extreme Events: Lessons Learned from Extreme Precipitation in Schwäbisch Gmünd

2020 ◽  
Vol 07 (01n02) ◽  
pp. 2050010
Author(s):  
Britta V. Weißer ◽  
Ali Jamshed ◽  
Jörn Birkmann ◽  
Joanna M. McMillan
Keyword(s):  
Extreme Events ◽  
Extreme Precipitation ◽  
Household Survey ◽  
Heavy Precipitation ◽  
Precipitation Event ◽  
Heavy Precipitation Event ◽  
Extreme Precipitation Events ◽  
Pluvial Flooding ◽  
Precautionary Measures ◽  
Precipitation Events

In 2016, heavy precipitation events in Southern Germany demonstrated that pluvial flooding can cause serious damages, not just in large cities but also in small and medium-sized cities. Hazard-oriented disaster management approaches to better address such spatially ubiquitous extreme events are already being developed. However, integrated strategies to reduce risk and to promote climate-resilient development pathways through both private precautionary measures and integrated urban planning are still underdeveloped. Considering the uncertainties associated with heavy precipitation, analyzing and understanding damages, strengthening people’s preparedness and improving preventative measures are central components of resilience building. This paper complements existing empirical studies on households’ preparedness and provides further insight into how resilience to flooding from heavy precipitation in cities can be strengthened. We do this by analyzing the damages caused by one particular heavy precipitation event, the preparedness of people in the affected city and their perceptions of responsibilities for improving precautionary measures. This paper presents the results from a household survey with a total of 1,128 completed questionnaires which was carried out in Schwäbisch Gmünd, Germany. The findings of the household survey illustrate the variety of damages caused by the heavy precipitation event and reveal important differences between households who experienced damages from pluvial flooding and those who did not. Lastly, findings of people’s perception about who is responsible for improved precautions offer interesting insights into tools that might help to enhance resilience building. Finally, the paper formulates recommendations for an improved assessment of resilience-building processes, individual capacities and planning tools to build climate resilience to extreme precipitation events.

scholarly journals The RainBO Platform for Enhancing Urban Resilience to Floods: An Efficient Tool for Planning and Emergency Phases

Climate ◽  
2019 ◽  
Vol 7 (12) ◽  
pp. 145
Author(s):  
Giulia Villani ◽  
Stefania Nanni ◽  
Fausto Tomei ◽  
Stefania Pasetti ◽  
Rita Mangiaracina ◽  
...  
Keyword(s):  
Flood Risk ◽  
Extreme Precipitation ◽  
Urban Areas ◽  
Early Warning Systems ◽  
Economic Losses ◽  
Urban Resilience ◽  
Multiple Sources ◽  
Life Project ◽  
Extreme Precipitation Events ◽  
Precipitation Events

Many urban areas face an increasing flood risk, which includes the risk of flash floods. Increasing extreme precipitation events will likely lead to greater human and economic losses unless reliable and efficient early warning systems (EWS) along with other adaptation actions are put in place in urban areas. The challenge is in the integration and analysis in time and space of the environmental, meteorological, and territorial data from multiple sources needed to build up EWS able to provide efficient contribution to increase the resilience of vulnerable and exposed urban communities to flooding. Efficient EWS contribute to the preparedness phase of the disaster cycle but could also be relevant in the planning of the emergency phase. The RainBO Life project addressed this matter, focusing on the improvement of knowledge, methods, and tools for the monitoring and forecast of extreme precipitation events and the assessment of the associated flood risk for small and medium watercourses in urban areas. To put this into practice, RainBO developed a webGIS platform, which contributes to the “planning” of the management of river flood events through the use of detailed data and flood risk/vulnerability maps, and the “event management” with real-time monitoring/forecast of the events through the collection of observed data from real sensors, estimated/forecasted data from hydrologic models as well as qualitative data collected through a crowdsourcing app.

scholarly journals Safer_RAIN: a Fast-Processing DEM-Based Algorithm for Pluvial Flood Hazard Assessment Across Large Urban Areas

2019 ◽  
Author(s):  
Attilio Castellarin ◽  
Caterina Samela ◽  
Simone Persiano ◽  
Stefano Bagli ◽  
Valerio Luzzi ◽  
...  
Keyword(s):  
Hazard Assessment ◽  
Urban Areas ◽  
Flood Hazard ◽  
Flood Hazard Assessment ◽  
Fast Processing

scholarly journals Analysis of precipitation extremes in the Taihu Basin of China based on the regional L-moment method

2016 ◽  
Vol 48 (2) ◽  
pp. 468-479 ◽  
Author(s):  
Zhengzheng Zhou ◽  
Shuguang Liu ◽  
Yan Hu ◽  
Yuyin Liang ◽  
Hejuan Lin ◽  
...  
Keyword(s):  
Urban Areas ◽  
Precipitation Extremes ◽  
Partial Duration Series ◽  
Site Analysis ◽  
Taihu Basin ◽  
Extreme Precipitation Events ◽  
Severe Flood ◽  
L Moments ◽  
Food Design ◽  
Precipitation Events

China has suffered from increasingly severe flood events in recent years, most of which are caused by heavy rains. The substantial casualties and damage caused by flooding necessitates a better understanding of precipitation extremes, especially in heavily populated urban areas. Based on L-moments from a regional perspective, this paper analyzes precipitation extremes in the Taihu Basin, utilizing annual maximum daily precipitation and partial duration series at 96 rain gages. The comparison of regional and at-site analysis results shows that the former provides more robust estimates, especially in the upper tail of a distribution (higher quantiles). Also, the use of partial duration series, which captures more information about extreme events, was found to be preferable to describe the extreme precipitation events in the Taihu Basin. Given the recently observed more frequent occurrence and greater magnitude of precipitation extremes, it is suggested that the food design standard used in the basin should be updated, especially for the urbanizing zones.

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