Results of research of the identification of flooding as a result of groundwater table fluctuations on the example of the valley of the River Vistula, with the use of multi-spectral Sentinel-2 images from the years 2017–2018 are presented. An analysis of indexes of water use, calculated on the basis of green, red and shortwave infrared (SWIR) bands, for extraction of water objects and flooded areas was carried out. Based on the analyses conducted, a mapping method was developed, using three water indexes (MNDWI Modified Normalised Difference Water Index, NDTI Normalised Difference Index and NDPI Normalised Difference Pond Index). Results show that the 10 metre false colour composite RNDTIGNDPIBMNDWI obtained significantly improved submerged extractions more than did individual water indexes. Moreover, the 10-m-images of MNDWI and NDPI, obtained by the sharpening High Pass Filter (HPF), may represent more detailed spatial information on floods than the 20-m-MNDWI and NDPI, obtained from original images.
During the last few years, the City of Bechar in Algeria has witnessed some extreme events, such as the great flood of the year 2008 in which an exceptional amount of rain was recorded with a flow rate of 830 m3∙s−1 (hwater = 4 m, b = 200 m); similar flooding also occurred in 2012 and 2014. The problem is that most of the City of Bechar has an urban sprawl that extends to the banks of Wadi Bechar, which represents a huge risk for the lives of the inhabitants of the region. The present work aims to assess the flood risk through flood hazard mapping. This method consists in determining the flow rates for the return periods of 25 years (Q25 = 388.6 m3∙s−1, hwater = 3.5 m, b = 200 m, Sspot = 55.35 ha), 50 years (Q50 = 478.3 m3∙s−1, hwater = 5 m, b = 200 m, Sspot = 66.48 ha) and 100 years (Q100 = 567.3 m3∙s−1, hwater = 7 m, b = 200 m, Sspot = 133 ha). For this, it is necessary to adjust the flow rates using Gumbel law along with some computer supports such as HEC-RAS, HEC-GeoRAS and ArcGis for mapping the event. Finally, this work enables us to determine the zones exposed to risk of flooding and to classify them according to the flood water height.
An initial step in flood hazard mapping is hydrological modelling. We present a recent river flood modelling approach in Bosnia and Herzegovina (BiH) for small ungauged catchments of drainage area up to 32 km2. To estimate peak flow of required probability in small catchments, we use the rational method. The paper focus is GIS based procedure for producing the runoff coefficient map for BiH from the DTM and land cover map. For validation of the peak flow modelling results in small ungauged catchments we use diagrams of peak flow per catchment area (specific runoff) versus catchment area in medium and large gauged catchments. The results indicate agreement in specific runoff for 100 and 500 years return period compared to reference runoff in gauged catchments and a mild drop in specific runoff for 20 years.
by Copernicus EMS, were already flooded before Storm Desmond and would continue to be for several weeks. Efficient monitoring of flood events is fundamental to minimising the impact on life and property. Satellite remote sensing, due to its wide field of view and continuous coverage, is widely used in floodmapping and monitoring. The Sentinel 1 mission is ESA’s most recent synthetic aperture C-band radio detection and ranging (RADAR) (abbreviated as SAR) satellite with floodmapping capability ( Malenovský et al., 2012 ; Amitrano et al., 2014 ), continuing the
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