Spatial Variation of Hypsometric Analysis in Nerwa Watershed

The hypsometric analysis (area-relief analysis) of drainage basins is an effective method for measuring the percentage of subsurface materials remaining in watersheds and highlighting the influence of slope leveling factors on them. This study aims to highlight the spatial variation of the values of the hypometric curve and hypsometry integral in the Nirwa basin and its sub-watersheds, and to detect the correlation and the influence degree between the values and the factors influencing them, The importance of the study lies in the fact that it discusses the results of applying mathematical equations to account the values of the hypsometric analysis that indicate the percentage of remaining land masses and the general topographical characteristics of the basin and their exposure to erosion factors, indicating the results in percentage and supported by a graph. The investigation concluded that the Wadi Nirwa watershed was in the late stage of the erosion cycle, and that more than two-thirds of the rock masses were removed in the watershed, as the values of its hypsometric integral reached 0.32%, and that the common category of hypsometric integral is 0.35-0.6%, as the values of 21 sub-watersheds ranged between 0.34-0.58%. The study also showed that the topographic characteristics are among the most influencing properties on the spatial variation of the hipsometric analysis values, and that the best model that can explain these variations is the model that consists of the variables of mean elevation, relative relief, slope average and dissection index.