CIVE 546 WATER RESOURCES SYSTEM ANALYSIS DECISION SUPPORT SYSTEM PROJECT 2016
Flood Control Simulation for Ciliwung River, Jakarta, Indonesia Neil Andika1 Jakarta is the capital city of the Republic of Indonesia. The city has an average annual precipitation of 1855 mm2 (73 in.). This high amount of precipitation, and in combination with bad drainage system, river management and sea level rise, flooding periodically occurs in Jakarta in wet season. It damages public infrastructures and results a huge annual economic loss. The purpose of this decision support system (DSS) for Ciliwung River is to help water manager to set gates opening along the river such that can be better mitigated to minimize the economic loss in the Ciliwung River’s watershed. Ciliwung River is chosen for this DSS prototype due to its critical role in flooding problem in Jakarta, high complexity and well-established supporting data. Based on that purpose, this DSS is expected to find the gates opening combination in Ciliwung River that give the minimum total economic loss for a specific flood discharge. The DSS also generates the total economic loss for specific gates opening. The DSS is made by using Microsoft® Excel which is very common tool in Indonesia. It can be accessed in 2 languages: English and Indonesia and only available in Metric Units. The analysis is done in each gate structure (node) and related with the next node. The DSS consists of 6 sections: introduction, interface, summary, model, results, and map. The introduction section briefly describes the purpose of the DSS and user guide. The interface section shows the simplified illustration of Ciliwung River with input data and important parameters for each river segment, including the total economic loss. The input data include the upstream inflow (discharge through upstream at the upper boundary of Ciliwung River), precipitation, gates opening and operational time of the gates. Those data are typically easy to understand, even for non-engineering users. The summary section provides a table of the input data and the calculated economic loss. The model section contains the calculation method for this analysis. The discharge upstream of a gate (Q US) is a summation of discharge through previous gate and surface runoff, where the surface runoff is calculated with rational method. Then, the upstream flow depth (h US) can be calculated based on the rating curve of certain cross-section (Q vs h). Hydraulic model (HEC-RAS) is used to produce the rating curve for cross-sections, and also the rating curve of gate structures. By applying the rating curve of gate structures with certain gate opening, the discharge through a gate (Qg) is determined for specific upstream flow depth. If the overflow discharge (DQ = QUS - Qg) > 0, there is high possibility that flooding will occur in the watershed of the segment and flood routing is required to analyze the flooding. The flood routing is done by using hydrologic model such as FLO-2D, and it 1 Graduate Student at Civil and Environmental Engineering, Colorado State University. Email:
[email protected] 2 Based on data from http://en.climate-data.org/location/714756/; accessed on April 28, 2016.
CIVE 546 WATER RESOURCES SYSTEM ANALYSIS will produce a graph of flood height and flood area in a function of DQ and operational time of the gates. As the DQ and operational time are known, the flood height is found from the graph, then the economic loss for a segment is found based on economic value of the area. The result is saved in the result page while map page shows the flooding area with parameters such as flood height and economic loss. In summary, the DSS flood control simulation for Ciliwung River is a combination of hydrologic model such as HEC-RAS and FLO-2D and also Excel to create a userfriendly platform. For the time being, the DSS is limited only for Ciliwung River with fixed number of gates structures. Another DSS with more flexible number of gates will be developed for analyzing all rivers and channels in Jakarta in near future.
