ABSTRACT



	Gendol River has always been impacted by the potential hazard of Mount Merapi. Pyroclastic flow effected to various sectors, which after the 2010’s eruption also occured debris flow. This debris flow damaged infrastructure sector including roads, bridges, irrigation channels, weirs, sabo dams, and drinking water pipe networks with a total amount of 196,3 billion rupiahs. The volcanic material from the eruption nowadays still remains sediment hazard to the ecosystem. Sabo dam is built to accomodate debris flow and also to control sedimentation along river, it holds certain volume of sediment. Therefore, this research was conducted to evaluate sabo dams’ storage capacity in Gendol River on controlling sediment.
	Sedimentation in this research is limited only from land erosion. The area of Gendol sub-watershed is calculated more than 11,48 km2. The research method used to estimate erosion is Universal Soil Loss Equation. Rainfall, soil type, topography, land coverage and conservation are factors which were analyzed using ArcGIS 10.3 . They are archives obtained from relevant agencies.
	The results of this research show that an estimation of 148.417,57ton/ha land erosion happen per year in Gendol subwatershed. Only 14,27% is estimated to be sediment equal to 9.007.356,15 m3/yr by assuming sediment’s weight density of 2,70 ton/m3. While the total capacity of all sabo dams along upstream Gendol River where GE-C Gadingan as the lowest point has only 1.839.291,07 m3of volume. This capacity is less than the sediment production in a year. So, this research concluded that the sabo dams can’t accomodate the sedimentation rate and due of that 7.168.065,08 m3 will flow through GE-C Gadingan. This number of sediment discharge will be controlled by ten sabo dams in the lower Gendol River.

Keywords: volcanic material, sedimentation, Gendol subwatershed, sabo dam.