A second feature are the `` wadis '' , which range from seasonal watercourses that flood only occasionally during the wet season to large `` wadis '' that flood for most of the rains and flow from western Darfur hundreds of kilometres west to Lake Chad .
A second feature are the `` wadis '' , seasonal watercourses ranging from small rivulets that flood only occasionally during the wet season to large `` wadis '' that flood for most of the rains and flow from western Darfur hundreds of miles west to Lake Chad .