Drainage analysis of mountainous watersheds in the emirate of Ras Al Khaimah, United Arab Emirates

INTRODUCTION

The United Arab Emirates (UAE) lacks any perennial rivers or streams. However, several Wadis of different categories and valley beds are present. The wadis are mostly dry, but they drain runoff to their regions only during the rainy seasons. The generation of runoff from rain behaves differently from one Wadi to another depending on the nature of the topography and the catchments. In the mountains, floods are the result of heavy rains where a small part of the rainwater infiltrates into the Wadi beds and thus produces quite a large flood discharge. Therefore, most of the annual precipitation reaches the plain, corresponding to a relatively high annual runoff. The average annual runoff from the major wadis in the United Arab Emirates is about 120 million cubic meters. [1]. In the piedmont areas, both infiltration and runoff are observed. Therefore, heavy rains can lead to runoff, even in a fairly permeable area (gravel plain). Much of the annual rainfall in this area flows into the dune area. In a region where runoff is almost non-existent, the only loss of water is due to evaporation. The loss of water is directly proportional to the number of rainy days and its depth.

Morphological parameters are the main factors influencing surface runoff generation, surface water production, peak flow, flooding, and groundwater recharge. Therefore, these parameters are necessary to estimate and analyze the aspects of flooding and recharge of the basins.

Surface water assessment is also essential for water management, including flood control, recharge assessment, and surface water utilization of a watershed. The drainage analysis was carried out through the analysis of morphological parameters, as well as the application of the rain-runoff model. In the present study, the Ras Al Khaimah area of ​​the Northern Emirates was selected for drainage analysis. Fig. 1 presents a location map of the study area. The largest among other wadis, Al Bih, was considered for rainfall and runoff evaluation.

II. CHARACTERIZATION OF MORPHOLOGICAL PARAMETERS

Every hydrological design is different because the factors that affect the design vary by location. Important factors such as geomorphological parameters and land use of the basin, as well as the amount of storage. Morphometric parameters have been used in various studies of surface water geomorphology and hydrology, such as flood characteristics and sediment production.

Morphometric analysis of any watershed provides information on the area’s topography, geological condition, and runoff potential. Morphometric analysis is the measurement of the three-dimensional geometry of landforms and has traditionally been applied to watersheds, drainages, hill slopes, and other groups of terrain features. [2].

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