Study on river morphology in Pabelan river after the Merapi eruption in 2010

Mount Merapi is the most active volcano in Indonesia. The dangers posed by Mount Merapi were hot clouds, incandescent lava, and cold lava. Cold lava floods will transport enormous volcanic material, causing an impact on the area around the downstream river. The main purpose of this study is to analyze changes in cross-section and longitudinal sections after the 2010 eruption, to analyze the value of aggradation and degradation. The method used is the method of analysis using DEM in 2008, and the Cross-Section of the Pabelan River in 2012 and 2015. Based on the result shows that significant changes in cross-sectional and longitudinal sections occur at point 52 + 0. Changes in elevation of point 52 + 0 have decreased in elevation from 2008 to 2012. The aggradation volume of sediment at point 33 + 0, at point 50 + 0 and at point 52 + 0 are 1,700,595 m3, 2,385,226 m3 and 1,354,799 m3, respectively. The degradation volume of sediment at point 57 + 0, at point 59 + 0 and at point 67 + 0 are 4,607,479 m3, 4,639,474m3 and 19,431,948 m3, respectively. The degradation tends to take place in the upstream area and aggradation occurs at the point that the sabo dam was contracted.