Mt. Merapi is one of the most active volcanoes in Indonesia. Some of rivers that the origin is located at Mt. Merapi have a large amount of sediment resources after eruption. So, the rivers have a potential of debris flow when the eruption occurs. The lava production will deposited at the upstream area and it flows to the downstream during wet season. Then the river has sediment resources in a large number. The flow that contains a large of sediment transport causes damages on river constructions. This phenomenon should be considered by engineering during make a planning for construction in the volcanic river. The lava production which deposited at the downstream area also attracts the people to conduct sand mining activities. Progo River has this phenomenon. Recently, the sand mining activities in Progo River is increasing dramatically due to the 2010 eruption of Mt. Merapi. So, the bed morphology on the downstream area should be consid