الفهرس 
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Abstract
Flash floods are typically natural hazards that occur infrequently in short duration with high flow peaks and high velocities in addition to the loss of life. Forecasting flash floods is difficult and there is a shortage of hydrological and meteorological data for the arid and semi-arid zones. So Governments in all countries of the world are paying increasing attention to research into flash floods which are becoming increasingly important, and to improve data collection techniques, warning systems and control measures as well .
Floodplains are the dry land areas located beside rivers and streams that inundated during flood events. Due to its beautiful view and convenient access to water recreation, floodplains are occupied by human activities and this occupation changes the characteristics of the stream cross section which leads to flash floods. Accordingly, Flood inundation mapping is an important tool for stakeholder’s to develop scenarios for control and manage the floodplains. For Wadi Watir, there are floodplains at the delta which are determined and many scenarios are suggested for management these areas from inundation.
Wadi Watir is located in South Sinai, Egypt. It is one of the most active wadis in Sinai which is exposed to flash floods every year. It faces a lot of disasters and damages from floods (e.g. those happened on Oct. 1987, 1990, and 1997). Wadi Watir has a catchment area of about 3520 km2. A lot of protection structures were constructed at the upstream of the catchment, as dams and lakes, distributed at many tributaries (Quadeira, shebeha, Sowana, etc.). Delta Watir has very important commercial, touristic, industrial and agricultural regions at floodplains; three dikes (north, south, middle) were constructed to protect these regions from floods with lengths 2750, 3700, 1500 meter, respectively. The height of these dikes is 4 meters in the delta upstream and it decreases to 0.5 meters at the delta downstream or at the Gulf of Aqaba .
II
Producing flood inundation maps requires an observed or simulated flow hydrograph. So HEC – HMS hydrological model was used to estimate the catchment main morphological parameters through the calibration of the observed flow recorded on 27 January 2013. Then the model was used to forecast the runoff values for 50 and 100 years return periods depending on the results of statistical analysis for rainfall data at Ras Al- Naqb – Nuweiba – Saint Catherine rain gauges, operated by GMA. The model uses the SCS curve number in estimating the infiltration losses and SCS unit hydrograph to convert the rainfall to runoff. On the other hand, the 2D Saint Venant equation (full momentum) was used through the hydrodynamic HEC – RAS 2D, in order to generate flood inundation maps at delta watir for two events observed event (January 2013), and 100 years predicted event considering the storage of existing protection structures located in the upstream using reservoir routing technique in HEC – HMS model.
The results of the hydrological model HEC - HMS ensured that this model has the option to predict flow hydrograph in comparison to the observed one. Also, the results of the hydrodynamic model HEC – RAS ensured that this model is suitable for simulating the movement of floods in two dimensions with different values of depths and velocities, in addition to determining the inundated areas .
Finally, flood inundation map at delta Watir for 100 years return period showed that there are inundated areas and this means that the existing protection dikes are insufficient to protect the delta. Therefore three scenarios are suggested to mitigate the inundation. The first scenario is to implement the safe zones from the floodway stream according to the flood inundation map. The second one is moving the damaged buildings to safer locations. While the third scenario is to increase the height of the existing dikes to prevent the inundation from extreme floods. This scenario is simulated in HEC- RAS and it is found that the flow restricted between the existing dikes. Finally, A comparison is created between the three scenarios and it is found that the third scenario is the optimal one due to its feasibility in implementation; also it keeps the Bedouins in their places.
On the other side, there are other methods for management that may be considered. One of these methods is called non- structural measures such as using flood warning system, the other is government preparations to control the floods and prevent the disasters.