Author(s): Warni Yati, Radianta Triatmadja, Nur Yuwono, Djoko Legono, Intan Supraba
Keywords: Tsunami; Hydrograph; Scouring; Seawall;
Abstract: Tsunami may run-up and overflow a sea wall that was designed as tsunami protection. Such overflow as happened in Japan in 2011 was capable of overturning the seawall by scouring the bed behind the sea wall. This indicates that a better design of downstream protection is required. A simulation of scouring due to tsunami at downstream of a seawall may need a long flume and relatively large flow discharge. Since along flume and sufficient pump capacity was not available, a short flume equipped with a tank was designed and used as the substitute. A water tank was placed above the flume to store water needed for the entire simulation. Before each simulation, water was pumped into the tank using a relatively small pump capacity which is normally available. Such an arrangement was possible as the duration of tsunami is normally limited, and thus the entire simulation needs a relatively small amount of water to be stored in the tank. A gate valve with an electronic controller was installed in the pipe system to control the release of water from the tank into the flume. The opening and closing time and duration of the valve make it possible to generate a certain tsunami flow hydrograph on land. A seawall model was installed in the middle of the flume to observe the behavior of tsunami overflow and the scour at the downstream of the seawall. The tsunami generator was capable of modeling the scouring at the downstream of the seawall. The dimension of the scour depends on the overflow discharge, the wall height and the material’s characteristic at the downstream of the seawall. Finally, a preliminary method to reduce the scouring was developed and presented.