Abstract
This paper introduces a new simple approach for dam-break hazard mapping in a data-sparse region. A hypothetical breaching case of an earthen dam, i.e., the Ketro Dam in Central Java, (Indonesia) was considered. Open-access hydrological databases, i.e., TRMM and CHIRPS, were collected and compared with the rainfall ground station data to ensure data quality. Additionally, the 3-h rainfall distribution of the TRMM database was employed and validated with the measured data to establish the 24-h rainfall distribution of the probable maximum precipitation. The probable maximum flood discharge was computed with the SCS method, and the reservoir routing computation was conducted to determine the possible breaching mechanisms. The result shows that the Ketro Dam proves safe against overtopping, and thus only the piping mechanism has been taken into consideration. Using the breaching hydrograph, the open-access Digital Elevation Model MERIT Hydro, and the high-performance shallow water model NUFSAW2D, the flood propagation to the downstream part of the dam was simulated, enabling fast computations for different scenarios. The quantification of the susceptibility rate of urban areas was eased with overlay analysis utilizing InaSAFE, a plugin for the QGIS model. This study shows that even for a data-sparse region, the recent open-access databases in terms of hydrological and hydraulic aspects may be used to generate a dam-break hazard map. This will benefit the related stakeholders to take proper action to reduce the loss of life.
Highlights
Dam-break is one of several hazardous events that must be faced by Indonesia, especially when considering the existence of numbers of old dams
This study aims to provide a framework of dam-break hazard risk mapping for the Ketro Dam by taking into account the use of a rainfall–runoff model in combination with satellite-based rainfall data to conduct the flood computation, the use of a high-performance parallelized shallow water model associated with a reliable DEM to promote dam-break analysis, and the implementation of the QGIS model to allow for the quantification of hazard and susceptibility rate of urban areas at the downstream of the Ketro dam
Applying the Extended Triple Collocation (ETC) method to all data delivers the results shown in Figure 8, indicating a better correlation between the TRMM and CHIRPS data than the rainfall ground station data
Summary
Dam-break is one of several hazardous events that must be faced by Indonesia, especially when considering the existence of numbers of old dams. Dam-break cases may be triggered by several factors, e.g., earthquakes and heavy rainfall, and the design of dams is subjected to the recent construction code and standards that take such factors into account, despite a low probability of exceedance. In other words, assuming no construction mistake, dams are theoretically safe from a breach event, as long as the value of the design earthquake or flood is not exceeded. While new dams are subjected to the recent construction code, old dams may no longer meet the current safety standards due to their material quality degradation over time. Another complex factor such as climate change may have caused the parameter designs for such old dams to change dramatically. The control and regulation by the related stakeholders may not always function well, causing poor quality maintenance
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