2 nd Scientific Conf. for Environment and Sustainable Development in Arid and Semi-Arid Regions, Ajdabiya, Libya, 14-16 Jan., 2014 DRAINAGE MORPHOMETRY AND ITS INFLUENCE ON RUNOFF OF EL-KOUF WATERSHED, NE, LIBYA – A REMOTE SENSING AND GIS APPROACH 1,2 Abdal Azim and Fawzi 1,2 , Samir Kamh 1 Wahed - , Mohamed Abd El 1 Mahmoud Ashmawy 1 Geology Department, Faculty of Science, Tanta University, Egypt 2 Geology Department, Faculty of Science, Omar Al-Mukhtar University, Libya ABSTRACT Morphometric studies involve evaluation of streams through the measurement of various stream properties. Drainage basins comprise a distinct morphologic region and have special relevance to drainage pattern and its hydrologic response. Quantitative description of these basins morphometry requires the characterization of linear and areal features, gradient of channel network and contributing ground slopes of the drainage basin. Thus, detail analysis of drainage parameters is of great help in understanding the influence of drainage morphometry on surface runoff. The present study aims to demonstrate the potential use of remotely sensed data and geographical information systems (GIS) in extracting and evaluating of linear, relief and areal morphometric parameters of wadi El-Kouf drainage basin and its network in Al Jabal Al Akhdar region. Moreover, to analyze the influence of these parameters on runoff conditions and risky of this drainage basin. Landsat 7 ETM+ and SRTM data as well as topographic sheets (1:50.000) were used as the source data, which processed in ArcGIS, Global Mapper, and Surfer softwares. The study reveals that the high values of some calculated parameters have great influence on the basin surface runoff. Among of them, large basin area (938 km 2 ), bifurcation ratio (4.45), and drainage density (1.57 m/km 2 ). In addition, this influence was demonstrated by the estimated maximum value of runoff in a rainy day by 15.5x10 6 m 3 /day, with high peak discharge of 119.94 m 3 /sec. On the other hand, the present study demonstrates that remotely sensed data and GIS based approach is found to be more appropriate than the conventional methods in extracting, evaluating and analyzing the morphometric parameters of the drainage basin and network of wadi El-Kouf. 1. Introduction Natural disasters occur frequently and their impact and frequency seem to have greatly increased in recent decades, mostly because of environmental degradation, such as deforestation, intensified land use, and the increasing population (Vincent, 1997, Pradhan, 2010 and Pradhan and Lee, 2010). With today’s complexity of society, response, and relief from disasters have become a serious concern (Youssef et. al., 2010). Flash floods are considered to be one of the worst weather-related natural disasters. They are dangerous because they are sudden and are highly unpredictable following brief spells of heavy rain. These types of floods and associated sediment transportation in arid regions receive a little recognition as environmental problems, due to the relative infrequent occurrence of runoff events and lack of observations (white, 1995 and Gheith and Sultan, 2002). Thus, the problems related to these floods should have a great attention and the constructing of the effective modeling to understand the problem and mitigate their disastrous effects is needed. Human activities such as unplanned