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.
Keterbatasan sebaran dan jumlah pos penakar hujan dapat diatasi pengukuran hujan berbasis satelit. Seiring perkembangan teknologi, pengukuran hujan berbasis satelit, seperti GPM menunjukkan akurasi dan cakupan yang semakin membaik. Tentunya penggunaan hujan satelit ini juga perlu disertai dengan proses validasi berupa koreksi yang semakin mampu meningkatkan performanya. Banyak studi evaluasi dan koreksi data satelit telah dilakukan, hanya ada studi terbatas yang telah dilakukan di Indonesia. Oleh karena itu, studi ini bermaksud untuk mengevaluasi performa data hujan berbasis satelit (GPM IMERG) dan melakukan koreksi dengan metode validasi silang Monte-Carlo di Bandung Raya. Secara spesifik, studi ini menitikberatkan pada perbandingan antara data GPM dan pos hujan melalui analisis statistik untuk hujan bulanan. Hasil menunjukkan bahwa, data GPM mampu mendeteksi pola hujan bulanan dengan baik. Data bulanan tersebut dikelompokkan berdasarkan musimnya dan menghasilkan korelasi hujan musim kering yang lebih baik pada musim basah. Koreksi dengan MCCV dengan simulasi 1.000 kali berdasarkan musim tersebut menunjukkan peningkatan performa rata-rata sebesar 70% untuk bias relatif, dan 30% untuk RMSE, di kawasan Bandung Raya.
A rainfall Intensity-Duration-Frequency curve serves vital purposes in urban water management, typically generated using a long historical rainfall record. In most cases, such measurement is often sparse or poorly done. Hence it becomes a significant challenge to derive this curve. However, many studies have demonstrated the use of satellite rainfall measurement to cope with this data shortage. One of them is TRMM 3B42 Daily, which is employed in this study. This paper presents the application of TRMM to derive a better IDF curve in a data-scarce region for urban water management. It takes place in Bandung, where most of the upstream catchment area has limited rainfall records. The result shows that the TRMM-derived IDF curve demonstrates underestimated rainfall intensity compared to the ground measurement one. Consequently, the correction of daily data TRMM is necessary to improve the performance of TRMM-derived IDF. The correction of daily TRMM has statistically improved the performance of IDF. It is exhibited by the decreasing value of RMSE and RE. This analysis was culminated by producing an updated IDF curve using TRMM data from 1998-2019 for Bandung City. There is no significant trend that appears in rainfall intensity from 2016-2019.
A spillway is one of many important components of a dam, which is operated to prevent the dam from overtopping. Spillway with gate structures requires to have a good operation pattern by considering a minimum critical height and outflow discharge to prevent any flooding events in the downstream part of the spillway channel. The case study in this research is the Delingan Dam which has two ogee spillways, four main sluice gates and four additional sluice gates. Located in Karanganyar District, West Java, Delingan Dam is considered as a vast infrastructure which is potentially threatening if the spillway’s operation is not optimal. This study aims to analyze the spillway gate operations’ pattern of Delingan Dam in order to control the flooding event. The methodology used in this study is flood routing by utilizing several scenarios in order to obtain the optimal simulation results. Five scenarios that were simulated on the designated flood discharge have various combinations on the number of gates and their opening, as well as the time in which the operation started. The results show that the operation only using ogee spillway still meets the criteria for minimum critical height and maximum allowable discharge for return period of 25, 50, and 100 year.As the discharge with 1000 year return period, half of PMF, and PMF,the recommended operation is, foremost, to occupy the main gate in which results in the peak outflow discharge of 23.65 m3/s, 62.4 m3/s, and 140.9 m3/s, with the minimum critical height of 1.45 m, 1.41 m, and 1.35 m, respectively. However, this operation is not adequate for the half of PMF, and the PMF discharge, since the capacity in the spillway channel is estimated about 24.7 m3/s.Keywords: spillway, flood control, spillway gate operation, the delingan dam
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