Modelling Water Flow Hydraulic in Open Channels with Green Drainage Facility
Ratih Indri Hapsari1, Roikhatul Jannah2, Moh. Charits3, Agus Suhardono4, Mona Shinta Safitri5

1Ratih Indri Hapsari, Department of Civil Engineering, State Polytechnic of Malang.
2Roikhatul Jannah, Department of Civil Engineering, State Polytechnic of Malang.
3Moh. Charits, Department of Civil Engineering, State Polytechnic of Malang.
4Agus Suhardono, Department of Civil Engineering, State Polytechnic of Malang.
5Mona Shinta Safitri, Department of Civil Engineering, State Polytechnic of Malang.
Manuscript received on 08 June 2019 | Revised Manuscript received on 30 June 2019 | Manuscript Published on 04 July 2019 | PP: 1064-1069 | Volume-8 Issue-1S4 June 2019 | Retrieval Number: A11990681S419/2019©BEIESP
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Abstract: High increasing of urban area in greater Malang Indonesia has been raising the water availability issues in surrounding river basins. Providing the green drainage system in residential area would be expected to contribute to the water sustainability in the sub-basin where the area is located. This study aims to design and evaluate the effectiveness of sustainable drainage channels and structures in a housing area in Malang Regency with area of 75,000 m2. The green drainage facilities includes pervious channel, permeable pavement, and retention pond. The data required are topographical map with 0.25 m interval, daily maximum rainfall rate from Lawang, Singosari, and Tumpang rain gauges, and soil properties. The design rainfall is analysed by Gumbel frequency distribution with ten years return period. Rational method is applied to calculate the design flood in conjunction with Kirpich and Mononobe method to analyse concentration time and rainfall intensity. Manning formula is used to design the channel dimension based on open channel hydraulic and uniform flow theories. The retention pond is planned by analysing the design capacity from the flood inflow and designed outflow hydrograph of the pond. The complexity of the hydraulic analysis considering the unsteady flow motivates the application of HEC-RAS one-dimensional hydraulic software. The analysis shows that the flood discharge in the primary channel is 5.007 m3/s using full asphalt pavement and 4.560 m3/s using permeable pavement. The dimension of the primary channel is designed as typical channel with 1.4 m width and 1.4 m height. Should the concrete channel is applied, the retention pond is designed to extend the flood timing of 3.578 minute and reduce the primary channel discharge of 0.070 m3/s. The analysis reveals that the adequate pond dimension is 30 m width, 20 m length, and 0.61 m depth. The pond could retain the water of 368.252 m3 volume, infiltrate the water of 26.280 lt/year to the ground water, and reduce the peak flood in the channel from 5.007 m3/s to 4.328 m3/s. The water level profile of steady flow is evaluated through HEC-RAS simulation. This analysis is important to assess the flow velocity, energy, and regime of the continuous channel in steady manner, which cannot be obtained directly from the initial Manning calculation. In addition, the unsteady flow caused by the existence of pond is simulated by HEC-RAS. The results demonstrate that the water stage and energy variation could be accommodated in the designated channels. This research is expected to provide benefit as consideration of the utilization of sustainable drainage facilities in development of urban area.
Keywords: Detention Pond, HEC-RAS, Flood Discharge, Drainage Channel.
Scope of the Article: Design and Performance of Green Building