Integration of remote sensing and GIS for modelling flash floods in Wadi Hudain catchment, Egypt

Abstract

Abstract:This paper presents a new approach to modelling flash floods in dryland catchments by integrating remote sensing and digital elevation model (DEM) data in a geographical information system (GIS). The spectral reflectance of channels affected by recent flash floods exhibit a marked increase, due to the deposition of fine sediments in these channels as the flood recedes. This allows the parts of a catchment that have been affected by a recent flood event to be discriminated from unaffected parts, using a time series of Landsat images. Using images of the Wadi Hudain catchment in southern Egypt, the hillslope areas contributing flow were inferred for different flood events. The SRTM3 DEM was used to derive flow direction, flow length, active channel cross-sectional areas and slope. The Manning Equation was used to estimate the channel flow velocities, and hence the time-area zones of the catchment. A channel reach that was active during a 1985 runoff event, that does not receive any tributary flow, was used to estimate a transmission loss rate of 7Ð5 mm h 1 , given the maximum peak discharge estimate. Runoff patterns resulting from different flood events are quite variable; however the southern part of the catchment appears to have experienced more floods during the period of study (1984)(1985)(1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000), perhaps because the bedrock hillslopes in this area are more effective at runoff production than other parts of the catchment which are underlain by unconsolidated Quaternary sands and gravels. Due to high transmission loss, runoff generated within the upper reaches is rarely delivered to the alluvial fan and Shalateen city situated at the catchment outlet. The synthetic GIS-based time area zones, on their own, cannot be relied on to model the hydrographs reliably; physical parameters, such as rainfall intensity, distribution, and transmission loss, must also be considered.

An early warning system for flash floods in hyper-arid Egypt

“…According to Gheith and Sultan (2002), only 3-7 % of the precipitation reached the watershed outlets for the Red Sea mountains (Eastern desert) in Egypt. El Bastawesi et al (2009) found for Wadi Hudain (Easter Desert) in Egypt that most of the runoff infiltrates into the alluvium during its transmission through the channel.…”

Assessment of waterlogging in agricultural megaprojects in the closed drainage basins of the Western Desert of Egypt

“…Therefore, the mapping of surface drainage channels and catchment outlets can be derived with reasonable accuracy using the space-born DEM such as the Shuttle Radar Topography Mission (SRTM) DEM (e.g. Ghoneim and El-Baz, 2007;El Bastawesy et al, 2009). However, the accuracy and reliability of the hydrographic parameters simulation using DEM are known to be influenced by source, resolution and processing algorithms (Zhang and Montgomery, 1994;Wolock and McCabe, 1995).…”

The Quaternary development of tributary channels to the Nile River at Kom Ombo area, Eastern Desert of Egypt, and their implication for groundwater resources

“…The catchments are ungauged, and this complicates the understanding of their hydrological processes. Remote sensing data can be used to derive relevant hydrological parameters such as the location of active channels and flood deposits, thus indicating the maximum inundation of channels and the most downstream points reached by the flows (El Bastawesy et al, 2009). The recent release of the MSS, TM and ETM satellite images archive of the United Sates Geological Survey (USGS web) for free download allows the close assessment of the active channels of different flash flood events in these dry land catchments.…”