2.3 Long-term gully volume change
Changes in both mean volume of the gully networks (V ) and mean
area-specific volume of the gully networks (Va )
for the two sub-areas from 1957 to 2005 were well approximated by
exponential functions (R2 = 0.99; Mukai, 2017). During
the entire study period, V of the gully networks in the two
sub-areas were almost the same scale, whereas Vaof the gully network in the Rift margin sub-area was always higher than
that in the Valley floor sub-area, and the gap between the two sub-areas
widened as time passed. The mean area-specific gully erosion rate
(AEM ) for the 12 catchments from 1957 to 2005 was 16.2 Mg
ha-1 y-1; 25.1 Mg
ha-1 y-1 for the Rift margin and
10.5 Mg ha-1 y-1 for the Valley
bottom sub-areas.