ABSTRACT
This
research is intended to assess the regional pattern of hypsometric curves (HCs) and
hypsometric integrals (HIs) for the watersheds draining into the Jordan Rift (River
Jordan, the Dead Sea, and Wadi Araba watersheds). Hypsometric analysis was performed
on 22 drainage basins using ASTER DEM (30 m
resolution) and GIS. The area-elevation ratio method was utilized to extract the
hypsometric integral values within a GIS environment. A prominent variation
exists in the HC shapes and HI values. The highest hypsometric values are found
for the Dead Sea ( = 0.87) and River Jordan ( = 0.77) watersheds. Whereas the lowest values ( = 0.51) characterized
Wadi Araba catchments, except Wadi Nukhaileh (lower
Wadi Araba) which yields an HI value of 0.26. Seventeen HCs pertained to the River
Jordan and the Dead Sea watersheds evince remarkably upward convex shapes
indicating that such drainage basins are less eroded, and at the youth-stage of
the geomorphic cycle of erosion. Catchments draining to Wadi Araba are of
intermediate HI values (0.41 - 0.58) which are associated with a balance, or dynamic equilibrium between erosion and
tectonic processes. Accordingly, they correspond to a late mature stage of
geomorphic development. Additionally, Wadi Nukhaileh yields the lowest HI value (0.26)
and is associated with highly eroded terrain of late mature geomorphic evolution,
approaching an old stage therefore, with distorted concave upward curves. High
HI values indicate that these watersheds have been subjected to tectonic
uplift, down faulting of the Rift and intense rejuvenation. Differences in HI
values can be attributed to disparity in tectonic uplift rate, base level
heights, and mean heights of the River Jordan watersheds, the Dead Sea and Wadi
Araba watersheds, and variation in lithology, which caused noticeable
differences in rejuvenation processes, and channel incision. Regression
analysis reveals that R2 values which represent the degree of
control of driving parameters on HI, are positive and generally low (ranging
from 0.026 to 0.224) except for the height of base level (m) parameter
which contributes 0.42 (significant at 0.1% level). Such results mean that the height of base
level has a significant at 0.1% level. It is
obvious that the most crucial driving morphometric factor influencing HI values
of the Jordan Rift drainage basins, is the height of base level (m).