Drainage organization on the newly emerged Dead Sea bed, Israel

The organization of distributary drainage systems on the emerging coastal areas of the Dead Sea was studied, following a rapid base-level fall of 24 m during the period 1945-2002 which made the emerging pristine coastal zone a natural field laboratory. Photogrammetric digital elevation models were extracted to identify different emerged areas and to quantify erosion and deposition processes. Visual interpretation of orthophotos was used in order to recognize different drainage networks and to delineate the receding shoreline. The remotely-sensed data were backed by field surveys including measurement of longitudinal profiles. The study demonstrates the spatial variability of runoff allocation from prograding fans to the emerging areas and the variable drainage responses. Three distinct environments were revealed on the emerged areas from the coast to the land: deeply incised channels which are the main transmitters of the base-level effect headward; dendritic coalescing systems that are the reversal of the diverging channel system on alluvial fans; and areas with unconfined sheet flowouts, which are detached from base-level control. The threshold gradient of erosion on the emerged areas is ∼3° Headward erosion was uncoupled with the lake level drop, i.e. the rate of headward entrenchment increased with time, despite an almost constant base-level fall.