Importance of taking into account DTM in three dimensions for the mapping of runoff potential, application to Lebanon.

摘要

Importance of taking into account DTM in three dimensions for the mapping of runoff potential, application to Lebanon. - Mapping water erosion at a regional scale is based on combining a certain number of factors, which do not have an equal importance with respect to the determination of the quantity of eroded soil. It is based on runoff potential map depending on physical environmental parameter characteristics and their behavior against erosion. Two maps of runoff potential were produced in a representative region of Lebanon. The first map (3 factors) was established from data on 1) vegetal cover, 2) density of hydrographic network and 3) slope gradient in degrees. The second (5 factors) integrates in addition to these data 4) slope aspect and slope curvature, issued from digital terrain model (DTM). Comparison of these two maps indicates an increase of the sum of polygons of 24 %, a concordance (or total precision) of 52 % and a. gaining of polygons limit of 38 %. Field verification (earth pillars) indicates that: 1) the units of the map 5 factors are more separated between them and 2) the total precision in the map 5 factors is equal to 82.5 % while that of the map 3 factors is equal to 42 %. Khi2 test shows a better coincidence between the map 5 factors and reality on the field. These results indicate the necessity and the importance of integrating slope curvature and aspect in order to evaluate the runoff potential at regional scale.