River Basin Organization of Cidanau-Ciujung-Cidurian (RBOC3) is a water authority in Banten Province that has the planning of six rockfill dams in development planning, i.e Karian, Pasir Kopo, Tanjung, Cilawang, Sindang Heula, and Cidanau Dam. Regarding to the emergency response plan, it is necessary to have an inundated area estimation due to a dam break. The objective of this study is to develop a flood hazard map based on dam break analysis in selected dams in Banten Province so that the flood situation can be understood. HEC-RAS software was utilized to simulate the two-dimensional flood propagation. The result shows that the total of inundation due to all dam failure is around 152 km 2 . The effect of this Karian Dam submerges 46% of the total area and volume of inundation from six rockfill dam failure. Also, Sindang Heula Dam and Cilawang Dam were considered as the second and third biggest impact on flood volume compared to the others dam break. This study can be used as the initial flood hazard map information in order to reduce flood damage in the future period under the massive construction. Furthermore, the result of this simulation could be applied to emergency response plans as the requirement of dam operation.

Flood is a natural disaster that can occur at any time and anywhere. The flood disaster causes material and non-material loss, then in order to increase the resilience to disaster, an early warning system is needed. The data is indispensable as a reference to make an early warning system. Unfortunately, flood assessment in purpose to record the data is often conducted much later after the event occurs. Therefore, this research was conducted to do modelling of flood hazard map is quantitatively and validated with observation data as a form of rapid flood assessment. The location of this study is in the Upper Citarum River Basin, around Bandung basin. The model is well done if the result shows the location of the flood as illustrated as the observational data. The result shows fair agreement with observed data where some points of inundated areas are captured and the location of inundated areas from modelling result looks similar to the inundated area from observation data.

The weir design process not only considers the location, dimensions, strength, and durability of the weir structure, but must also be consider the effect on the flow characteristics in the river after the weir, especially related to the flow velocity characteristic around the weir. The water level will rise and affect the flow velocity downstream of the weir. Because of the fall of water, the velocity will greatly increase and the river can erode. The weir construction on the Batang Asai River, specifically located in Sarolangun, Province of Jambi, has unique conditions that cause the velocity of water after the weir to increase. Several alternatives will be analysed as solutions to deal with changes in flow velocity. The alternatives are groundsill, riverbed normalization, and river crossing widening. It was found that the alternative of river widening showed a significant reduction in flow velocity.

Floods and drought have been essential aspects of the water issue for over the past 50 years. Several studies have found that they are caused by massive land cover and climate changes. Many climate change studies have been conducted to establish their characteristics using historical data. However, land cover change is a human need that inevitably has to be undertaken to improve the standard of living. Changes in land cover affect the response of land to rainfall, which inevitably affect the amount of run-off generated into rivers. Discharge, land cover, and rainfall are variables that are related to each other. By understanding one variable, we can understand the condition of others, which can describe the situation of the catchment area. This study aims to determine the rain, land cover, and discharge trends in the Citarum Hulu -Majalaya Basin. The historical data obtained by the ground station were used to analyze the rainfall and discharge. A hydrology model was used to establish the change in the land cover parameters, specifically a semi-distributed SWAT model. The non-parametric Mann-Kendall test was employed for the trend analysis and was applied to the annual maximum rainfall and discharge data and the curve number (CN) values. The results show the three are positive trends in maximum rainfall and CN value which affect the discharge value.

Flood is one of the natural disasters that occur in Indonesia frequently. At least there are 8.498 occurrences since 1980 through Indonesia. In order to prevent and resolve that natural disaster, some actions should be done. To know the best solution to solve flood, we should know the flood characteristic (what causes it, the inundation area, the height, how long it occurs, and etc.). The characteristic of flood will be easily known only when the flood occurs. Thus, it is necessary to build a model with high accuracy. The model was obtained by re-modeling the inundation incident that happened on March 7th, 2018, and validated with observed data from several locations in that period. The result shows a good agreement with the observed data. This is evident from the extent and depth of the puddle from the modeling results similar to the value of field observation data. From the results, it can be concluded that the Cikalumpang River model has been obtained with a good correlation. From field observations, it is known that flooding is caused by quite complex problems, such as decreasing river capacity due to illegal building construction, sedimentation, land cover change, and climate change.