Abstract.A dam break induced-flood propagation modeling is needed to reduce the losses of any potential dam failure. On the 25 July 2013, there was a dam break generated flood due to the failure of Way Ela Natural Dam that severely damaged houses and various public facilities. This study simulated the flooding induced by the failure of Way Ela Natural Dam. A two-dimensional (2D) numerical model, HEC-RAS v.5, is used to simulate the overland flow. The dam failure itself is simulated using HECHMSv.4. The results of this study, the flood inundation, flood depth, and flood arrival time are verified by using available secondary data. These informations are very important to propose mitigation plans with respect to possible dam break in the future.

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Abstract. Depth averaged equations are commonly used for modelling hydraulics problems. Nevertheless, the model may not be able to accurately assess the flow in the case of different flow regimes, such as hydraulic jump. The model requires appropriate numerical method or other numerical treatments in order to simulate the case accurately. A finite volume scheme with shock capturing may provide a good result, but it is time consuming as compared to the commonly used finite difference schemes. In this study, 1D St. Venant equation is solved using Artificial Viscosity Lax-Wendroff and Mac-Cormack with TVD filter schemes to simulate an experiment case of weir overflow. The case is chosen to test each scheme ability in simulating flow under different flow regimes. The simulation results are benchmarked to the observed experimental data from previous study. Additionally, to observe the scheme efficiency, the simulation time between the models are compared. Therefore, the most accurate and efficient scheme can be determined.

The height of canal blocking has a significant influence on re-wetting peatland, depending on the canal’s distance. An effective canal in good condition has to raise the groundwater table to -0.4 m below ground level according to the Indonesian Ministry of Environment and Forestry (MENLHK). The effectiveness of different canal blockings was modeled by Freewat software with variation of canal distance (200 m, 250 m, 300 m, 350 m, and 400 m) and blocking height (0.2 m, 0.3 m, 0.4 m, 0.5 m, 0.6 m). This simulation was carried out using recharge and evapotranspiration data covering 20 years. The input of the conductivity value was done using 50 m/day according to the calibration. From the modeling, 0.6 m high canal blockings give a satisfactory result at every canal distance. The study took place during the annual dry season, when recharge was almost zero and average evapotranspiration was 6 mm/day. Adjusting the canal blocking to a maximum of 0.6 m and the canal distance to 400 m, the groundwater table slowly rose 0.38 m and it took 30 days to reach full-re-wetting capacity. This study revealed that the effectiveness of canal blocking is directly related to evapotranspiration and recharge, which has a positive correlation with the groundwater rise and the re-wetting period.

Floods, one of classical disaster occurrences, are difficult to identify accurately; most of the incidents have no recorded predictions and floods are generally frequent events with poor data acquisition. Development of a flood database system has become important for improving the management of information with regard to a flood early warning system for vulnerable communities along the flood area. In the case of the Upper Citarum river basin, flooding has occurred since the 1960s and was still happening up until 2010, even though a lot of study has been done and infrastructure has been built. Numerical modelling (using hydrology and hydraulics model) are usually employed to simulate the flood area (Ag), flood depth (hg), and travel time (tpr). However, numerical modelling for flood prediction is too time-consuming to be useful as an early warning system for the mitigation of flood-related damage and loss. Therefore, this model was used to develop a flood database system, based on hypothetical data, in order to develop a recognition pattern for a neural network learning process that will improve the speed and accuracy of flood prediction. To improve the accuracy of numerical modelling and observation, an adjustment was established for an advanced training process which used a generalized regression neural network. In other words, the training and testing data sets were obtained by correcting near-field hydrograph numerical models from hypothetical rainfall.

The Bandarudara Internasional Jawa Barat (BIJB) and Kertajati Aerocity are under construction and expected to be a center of economic activity supported by potential of natural resources and agriculture. They later will act as a driver of economic growth in West Java, especially for surrounding area such as Kertajati, Jatitujuh and Ligung Sub-districts. As an affect of the the development of BIJB and Kertajati Aerocity, the water demand of surrounding area will increase. Therefore an analysis of water demand and availability is needed. This research supports by analyzing the water balance, water demand, and also water allocation using WEAP (Water Evaluation and Planing) software tool. Water balance of Cimanuk-Tomo, Cimanuk-Monjot, and Cilutung-Dam Kamun river are analyzed, water demand of the three sub-districts are also projected and become the inputs of the water allocation model. The result of WEAP model simulation shows that the Cimanuk River can meet the water demand of the three sub-districts until 2040.

Way Ela dam is a dam to be built in the Negeri Lima village. In the negeri lima village there was also a dam that formed naturally by landslide due to high rainfall on 13 July 2012. A year after it was formed, on 25 July 2013 flooding occurred due to an extreme rainfall that caused the failure of the natural dam. The event of the failure on 2012 generated flood that severely damaged houses and various public facilities to negeri lima village down toward to the coast. As a result of this event, a small-scale reservoir is formed. The Government plans to utilize the established reservoir to build the new Way Ela Dam. This study was conducted to analyze floods with scenarios in the event of a failure in the new Way Ela Dam. The overland flow is simulate with two dimensional numerical model HEC-RAS v.5. Determining strategies for mitigation needs to be assessed comprehensively, by simulating disaster scenarios on the dam, analyzing the impacts and then planning recommendations for disaster risk. The results are expected to be a reference for mitigation plans for the new Way Ela Dam.

Shortage of irrigation water supply in dry season prevents many farmers from growing their crops, and the annual benefit from agricultural products will decrease as much as the area of irrigation fields which have lack of water. The objective of this study is to determine the maximum benefit from agricultural products based on water availability, by determining the appropriate cropping pattern and maximum planting areas through linear programming. The case-study location is at Leuwi Kuya Irrigation Region. Planting schedule is selected based on minimum water shortage from simulation of 6 alternative planting schedules. Then, the best pattern of cropping (planting method and the total area) is determined using linear programming. Optimization is carried out in 3 scenarios with various planting methods (conventional and SRI), minimum irrigation water demand (class-area system), and schedule for beginning of the 3-growing seasons annually. Result of this study is the optimal area of the irrigated region that can be planted based on the water availability. The maximum benefit is 89 billion rupiahs, using SRI planting method and distribution of three groups of irrigation fields in water supply schedule.