Early Warning Model for Disaster Mitigation of Sediment Discharges in Watersheds TEDJO MULYONO(a*), JUMI(b), AZIZAH(b)
a)Department of civil engineering Politeknik Negeri Semarang, Central Java, Indonesia, b) Department of Bussisess Administration, Politeknik Negeri Semarang, Central Java, Indonesia
Erosion processes - sediment discharges at the watershed scale, occurring on sloped land and in channels or rivers. Starting with the occurrence of rain, the process of sediment discharge in sloped land is affected by rain and surface runoff, the process can be represented as sediment storage in sloped land, and the process of sediment discharge in channels or rivers supplied by sediment material from sloped land, bottom erosion and river banks, then the process can be represented as a sediment reservoir in a river or channel. Therefore prediction of sediment discharges in watersheds can be done with the concept of a storage model that is the model that is represented to respond to sediment discharges in watersheds. One model with the concept of storage is a tank model. The specific objective of this research is to develop a tank model for prediction of sediment discharges in the watershed at the recession limb when rain is complete. The method used in this study is to use a computational simulation method to obtain optimum tank model parameters including stages: Setting field experiments, Tank Model Analysis Settings namely formulating and analyzing tank models for prediction of sediment discharges in watersheds (hydrographs) at recession limbs when rain has finished. The analysis shows that 4 tank models can be developed for prediction of sediment discharge in the Watershed. Configuring a good tank model for prediction of sediment discharge in the watershed is a model composed of 1 (one) tank consisting of 2 (two) side holes, a representation of the amount of sediment discharge and 1 (one) bottom hole, a representation of the amount of sediment deposits, which applied in the Kreo Sub-watershed. The parameters values and constants for the 1 (one) tank model for the Kreo Sub-watershed are a1 = 0.473; a2 = 0.111; a0 = 0.053; ha1 = 50,608 mm; ha2 = 2.544 mm, Ha = 0.415 mm; Ch = 168.83 mg / liter. The values of the tank model parameters in the watershed have different values according to the condition of the watershed under review.
Keywords: discharge; sediment; prediction; rain; tank