| Summary: | Mount Merapi erupted again on the 25th, 26th and October 29th, 2010 and the largest
eruption on the dawn of 5 November 2010. This eruption released material which was
estimated at 40 million m
3
, in various forms, come to Gendol River. In Gendol River has
built facilities sabo dam building as many as 22 dams untill 2011, with a total storage
capacity of 1.2 million m
3
. Of the gap between the supply of sediment and the ability of sabo
dam construction, it is necessary to study the sediment management taking into account the
existence of sabo dam.
Eruption affects a wide cross-section and increase the slope of the dynamic, so the sediment
load in the sabo dam construction to increase, which exceeded the plan capacity of the sabo
dams, both volume capacity due to pyroclastic flows suspended (VH1), Volume Control
(Vc), Dead Storage Volume (Vds ) and Volume which held at the bottom of the River (Vh2).
The next impact is that runoff flowing entirely rainfall only, influenced by the volume of
sediment transported triggers that go into upstream sabo dam construction (Vs). The
cumulative value of Vs obtained along the river Gendol each return period, amounting
283,604.38 m3 (1y), 586,524.27 m3 (2y), 706,522.93 m3 (5thn), 776,826.32 m3 (10y),
857,879.77 m3 (25y) , 913,663.71 m3 (50y) and 966,151.88 m3 (100y).
One of the non-structural efforts that have been done by the government in managing with
floods of lava is the normalization. Definition of normalization in this paper is an attempt to
capture sediments with the aim of restoring the function of sabo dam building, in the hold,
accommodate and control sediment, no come to outward river and influance to disaster. The
review was based on sediment balance formula Shimoda (1995) by using a variable
normalization function sabo dam building and return period of rainfall. Normalization
scheme consists of five scenarios, namely Natural / Without normalization, normalization on
VH1, the Vc Normalization, Normalization at Vds, and Normalization on Vh2. While the
plan uses a variation of return period, there are 1, 2, 5, 10, 25, 50 and 100 yr.
The review concluded that the normalization can be chosen as the technical structural
engineering for sediment management. Furthermore, the re-normalization can be indicated
from the intensity of rainfall and the amount of rain that occurred, with due regard to the
circumstances that occurred in the field, related to rainfall, mining activities and conditions of
sabo dam.
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