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The area of the campus of Institut Teknologi Sepuluh Nopember (ITS) and its housing complex are usually inundated during heavy rain. It is because the slope of the land in the campus generally flat. Moreover, it is because some of the drainage channels contain sediment that reduce the optimum capacity of the channels. Hence, an evaluation of the drainage system of ITS needs to be conducted.
The steps of doing this evaluation are (i) identification of the existing problems, (ii) collection of primary and secondary data, (iii) literature review, (iv) calculation of capacity of the existing channels, (v) calculation of runoff, and (vi) analysis of the existing retention ponds. The primary data includes flow direction, the slope of channels, dimension of channels, and thickness of sediment in the channels. The secondary data comprises of rainfall intensity, Master Plan of ITS, and land-use. The calculation includes engineering design, bill of quantity (BOQ), and budget. A standard operation procedure for maintenance of drainage system to make the channels optimum is also suggested.
From the analysis, it is shown that the maximum daily rainfalls are 136.09 mm/day for 5 year-rainfall return period and 159.19 mm/day for 10 year-rainfall return period. The cause of inundation in ITS is there are some channels which are not connected to each other. As a result, the drainage water cannot flow easily to receiving water body (river). Another cause of inundation is the slope of some channels that does not properly made. The inundation of some roads is because there are no street inlets such that the water could not flow to the side channels. It can be concluded that (i) it needs some addition of secondary channels and box culvert in some areas, (ii) the slope of some channels need to be rearranged, (iii) 288 street inlets must be constructed along the planning area.