SIMULATING THE EFFECTS OF DREDGING TO THE RIVER HYDRAULIC CHARACTERISTICS OF THE AGUSAN RIVER USING LIDAR-DERIVED DIGITAL TERRAIN MODEL

摘要

Dredging is known to be the simplest and cost effective way to address the flooding in the rivers by widening and deepening its channels. It is a process wherein materials from the bed or banks of the river are removed and are disposed to a different location. Although this method would increase the capacity of the river to contain and prevent flood waters from spillage, this also causes the flow of the river to become faster going downstream. In this paper, we present the possible effects of dredging to the hydraulic characteristics of a river with the use of high spatial resolution LiDAR-derived Digital Terrain Model (DTM), field surveying, hydrologic modeling and 2-dimensional hydraulic modeling. The analysis involved the comparison of hydraulic simulation results between the models with actual river profiles and hypothetical or dredged river beds at different volumes. The 2D simulations generated several hydraulic characteristics that are to be compared; namely, the river velocity, flood depth, and stream power. The analysis was conducted in Agusan River, Caraga Region, Mindanao, Philippines; wherein industries of fishponds in the estuarine area and water transportation are existing and are currently operating. Aside from simulating the normal flow of the river to the different models, rainfall scenario based events of 2-year, 5-year, 10-year, 25-year, 50-year and 100-year return periods are also simulated and generated with the different hydraulic characteristics. The result of the analysis provides a quantitative approach in determining the maximum limit of volume of soil to be removed on a dredging activity to allow safe navigation for local fishermen in the estuarine areas and serves as an effective tool for monitoring if ever the local government unit are planning or wanted to conduct dredging in Agusan River.