Quantitative Assessment of Surface Runoff in Al - Karath Valley- Tobruk- Northeastern Libya

A Hydro Morphometric Study

Abstract

The Al-Karath Valley basin is one of the Valleys of seasonal flow. It covers an area of (15701590m²) located within the domain of the  municipality of Tobruk, Northeast of Libya, The study is based on the technique of remote sensing to determine the types of soil covers  of the study area through depending on the American Soil Conservation Hypothesis, known as (SCS-CN), in order to estimate the size of surface runoff in the basin considering the highest rainstorm. This study also relies on the topographic map of Tobruk with the scale of (1: 50,000), as well as, the field measurements due to the small size of the basin and the lack of clarity of some natural characteristics. It has been shown through the study that (48%) of the basin area has low permeability that helps to generate the surface runoff in a short time from one rainstorm. The runoff volume of the highest rainstorm has reached (77.7 mm) fell on the basin with the volume of (494,600 mᶟ) and at a surface flow velocity of (1.48 mᶟ /s) The concentration time (31 min) which is a very short time that increases the flood risks when sudden rain falls; a case that is distinguished in the area of the study.