Description

Description
Indonesia is one of the most tectonically active regions of the world, where the Australian plate subducts under the Eurasian plate at a velocity of 6-7 cm/yr. The resulting high stress rate is generating a number of geological phenomena which make this region one of the most affected by different types of geo-hazards, as Earthquakes, Volcanic eruptions, landslides, ground subsidence.
We focused on two sectors of Western Java where most of these hazards are present together with flooding and tsunami hazard, and where a large population is at risk.

In this case study, the flood risk and earthquake risk are evaluated for Western-Java. The results are validated against local observations and existing studies.
Also this case study has been defined within a multi-hazard framework. In fact, a flood model able to take into account subsidence scenarios has been developed in Jakarta.

Jakarta is the capital and largest city of Indonesia with a population of more than 10 million. It is located on the northwest coast of Java, in a low, flat basin, at elevations between −2 to 50 meters above sea level. About 40% of the city is below sea level and is prone to coastal and fluvial flooding. Moreover, Jakarta is sinking at a rate of 5 to 10 cm annually and even more in the coastal areas. There are plans to build a dike around Jakarta Bay, which will be equipped with a pumping system and retention areas to defend against seawater.
A SubGrid model was developed for a coastal area of Jakarta called Pluit. The model has a variable grid resolution of 50 to 800 m, but the water depths that are calculated by this model are downscaled to 50 m based on the TanDEM-X DEM. Several versions of the model were made to represent subsidence scenarios for 2010, 2015 and 2030. The RASOR end-user can define a sea water level time series, select a subsidence scenario, run a simulation and view the results or use them in a risk assessment.

Another part of the case study focused on the Bandung area.
Bandung is the capital of West Java province and Indonesia’s third largest city, with a population of 2.4 million. It is located 768 m above sea level and is surrounded by volcanic mountains. Regular flooding in Bandung presents a real and dangerous ongoing problem. The areas south of the city center are most prone to flooding from the Citarum River and its tributaries.
A Wflow hydrologic model at 250 m grid resolution was developed to simulate the rainfall runoff from the mountains that surround Bandung. The DEM for this model was derived from SRTM90. This runoff is than later used as input to a smaller area SubGrid 2D flood model.
The end-user can define uniform rainfall scenarios through the RASOR platform web interface or select a historical period of TRMM rainfall. The user can also select an initial soil moisture condition (dry, medium or wet) that represent respectively typical conditions during the dry season, annual average and conditions during the wet season (December-January).
The river flows in several rivers and larger streams as computed by the Wflow model are ingested into a smaller area SubGrid flood model at a varying grid resolution of 100 to 800 m. The water depths from this model are later downscaled to 50 m based on the TanDEM-X DEM. Several versions of the model were made to represent subsidence scenarios for 2010, 2020, 2050 and 2100. The user can select either of these models through the RASOR web interface to run a simulation for a particular subsidence scenario. The Bandung SubGrid model calculates the flood pattern caused by overflow of the Citarum River.

Indonesia – Jakarta. Impact assessment at building block scale for different subsidence scenarios. 2015 Subsidence scenario.

Indonesia – Jakarta. RASOR allows to evaluate the damage at different scales, getting the level of detail of the building footprints.