EXERCISE: LAND USE CHANGE ON WATER QUANTITY a. Figure Q1 shows hydrograph generated during rainfall event from an urban area with 90% of impervious surface. The urban area always experiencing flash flood. This issue always being discussed by the local authority. As the engineer in the local authority, you are responsible to solve this issue. One of the solutions proposed is to reduce the percentage of impervious surface to only 60%. i. Discuss in detail, the impact of reducing the percentage of impervious surface will affect the peak discharge (Qp), time to peak discharge (tp) and total discharge (Qt) of the hydrograph. ii. Sketch the new hydrograph in Figure Q1. Discharge 10 8 6 4 2 0 1 2 3 Time Figure Q1: Hydrograph during 90% of impervious surface

For the soils that are classified by the following AASHTO symbols, what would be the most likely USCS symbols? (Reference: Liu, 1970) Gravels sands: A-l-a, A-l-b, A3, A-2-4, A-2-5, A-2-6, A-2-7 Fines: A-4, A-5, A-6, A-7-5, A-7-6

For soils that are classified by the following USCS symbols, what would be the most likely AASHTO symbols? (Reference: Liu, 1970) Gravels: GW, GP, GM, GC Sands: SW, SP, SM, SC Fines: ML, CL, MH, CH