1. Flood Risk Assessment for Non-Gauged Watersheds
Omar Elbadawy
CEDARE
More than nintypercentof the Egyptian territories are classified as arid and hyper arid
desertregions.Inmanylocationsthe desertischaracterizedbythe presenceof an intense wadi
system, which is subjected to harsh climatic conditions, and extreme water scarcity.
Nevertheless,manyof suchwadiesexperienceextreme precipitationeventsinthe form of flash
floods,where aconsiderable amountof rainfalloccurs,suddenly, for a short duration, and with
a long period of recurrence. Efforts are therefore directed to serve two objectives: (1) Making
use of the available waterduringrare precipitationevents, and (2) Protection against potential
damage associatedwithflashfloods. A methodologyforfloodpredictions, risk assessment, and
vulnerability estimation is seen to be in evitable.
In the last few years, a considerable amount of attention has been devoted to the
development of the Eastern Desert of Egypt especially Al Soukhna area which is located at the
north of the Gulf of Suez.Al Soukhnaareapresentsagreat potential fordevelopment programs
including touristic resorts, industrial zones and new port. The area is embedded within a
network of active watersheds, which are subjected to recurrent flash flooding. In some cases
these flash floods cause damage to roads and infrastructure. On the other hand the area is
classified asaridzone which,ingeneral,islimitedinwaterresources.Toensure the sustainable
development in this area, an assessment for flash flooding potential, and vulnerability of the
watershedslocated inthisareashouldbe carriedout. Limitedwatersheddataare available from
digital elevationmodel (DEM) andrainfall records. Therefore a suitable approach that depends
on such limited data should be applied to study those watersheds.
The objectives of the study are:
1- Developing a user friendly program to demonstrate the different characteristics of the
watersheds using Geographic Information System (GIS) techniques.
2- Developing a methodology for flood risk assessment and relative vulnerability
classification for watersheds associated with wadi systems in arid regions.
3- Applyingthe proposedtechniquesandmethodologies for Al Soukhna area as a case study
to demonstrate their capabilities and efficiency.
The study isdirectedtowardsdevelopingamethodology for flood risk assessment and relative
vulnerability classification for watersheds associated with wadi systems in arid regions.

2. Geographic Information System (GIS) is used as the main analysis tool for modeling Al Sokhna
area.Watershedsin the study area have been identified, and geomorphology parameters and
watershed characteristics have been estimated. Nine parameters which mostly affect the
watershed'sresponsehave beenselectedtoclassifythe watershedsaccordingto flood risk. The
runoff hydrographs of NASH method have been compared with the proposed vulnerability
classification. The results of flood risk classification compared well with the estimated runoff
peakdischarge andtime to peak.GIS hasproved,as expected,tobe an easyand efficienttoll for
watersheds flood risk assessment