In: Horizons in Earth Science Research. Volume 5 ISBN 978-1-61209-923-1 Editor: Benjamin Veress and Jozsi Szigethy, pp. © 2011 Nova Science Publishers, Inc. Chapter 13 FLASH FLOOD FROM THE SPACE: A CASE STUDY FROM W ADI EL-ARISH CATCHMENT , SINAI PENINSULA, EGYPT ElSayed Hermas  and Mohammed El Bastawesy Geography Department, Umm Al-Qura University, Mecca, KSA ABSTRACT The catchment of Wadi El-Arish is the largest in Sinai Peninsula. Several flash floods events occurred during the last century and severely affected El-Arish City at the catchment outlet on the Mediterranean coast. El-Rawafaa Dam was constructed on the main channel of the catchment to minimize flash flood hazards on El-Arish City, and to maximize harvesting the fresh water from these flash flood events. Although the previous flash flood events had been originated from the upstream catchments of Wadi El-Arish, the 17 th of January 2010 storm that hit the area, and developed a catastrophic flash flood was mainly created by the flow of the northwest and northeast sub-catchments of Wadi El-Arish. These catchments have their outlets downstream of El-Rawafaa Dam and their main transportation channels are covered by the aeolian deposits. In response to that storm, the active channels of these sub-catchments were reactivated and incised through the aeolian deposits to eventually converge with the main trunk valley of Wadi El-Arish resulting in potential flash flood. The multi-temporal Landsat TM and ETM+ satellite imagery dated 1986, and 2003 were used to identify the active channels and their contributing sub-catchments associated with flash flood events. While the LandSat images dated 1986 and 2003 indicated that the upstream sub-catchments were active and successfully contained by the Dam, the EgyptSat-1 image dated February 2010 implied that the flow was originated from the downstream sub-catchments that converge with the main channel north of the Dam; thus developed uncontrolled flash flood. This case illustrated the potential of the multi-temporal satellite imagery to supplement routine hydrological monitoring at gauge stations in order to overcome the lack of data in the dryland environments.  Tel: +966 252 70 000: Fax: +966 255 64 560, e-mail: eaibrahim@uqu.edu.sa