The Changes of Runoff with DEM Resolution Variations
Elvi Roza Syofyan1, Bambang Istijono2, Amrizal Saidi3, Revalin Herdianto4

1Elvi Roza Syofyan*, Civil Engineering Department, Politeknik Negeri Padang, Padang, Indonesia.
2Bambang Istijono, Civil Engineering Department, Faculty of Engineering, University of Andalas, Padang, Indonesia.
3Amrizal Saidi, Soil Department, Faculty of Agriculture, University of Andalas, Padang, Indonesia.
4Revalin Herdianto, Civil Engineering Department, Politeknik Negeri Padang, Padang, Indonesia.
Manuscript received on March 16, 2020. | Revised Manuscript received on March 24, 2020. | Manuscript published on March 30, 2020. | PP: 2531-2538 | Volume-8 Issue-6, March 2020. | Retrieval Number: F8511038620/2020©BEIESP | DOI: 10.35940/ijrte.F8511.038620

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Abstract: Currently there has been a research gap in providing sufficient and reliable data for the estimation of surface runoff from ungauged catchment in Batang Kuranji watershed, City of Padang, West Sumatera, Indonesia. The need for such data arose from the fact that land cover changes occur rapidly in the past 20 years, and flash flood and river degradation have been experienced at an alarming scale. However, due to lack of discharge data from upstream catchment, modelling catchment response to the effect of land use changes is hampered. Field measurement is difficult due to accessibility to river tributaries in the upstream catchment. Therefore, the use of digital satellite images and digital elevation model is studied with various DEM (Digital Elevation Model) resolutions for the first time in this catchment. This catchment is situated from 95 to 1858 m above sea level with an annual rainfall of 3440 mm. This watershed is classified as steep with a watershed that has a slope of more than 40% reaching 37.01% of the entire Kuranji watershed area. This study used 30 m and 8 m DEM. Secondary data were gathered from satellite images such as MODIS (MO Derate resolution Imaging Spectroradiometer) Land Use. Precipitation data were gathered from three rain gauging stations in or nearby the catchment. Stream geometry data were obtained from the Provincial Office for River Management. Annual discharge and 100-year discharge are calculated using rainfall data for the past 20 years. Runoff discharge was calculated using rational method and SCS (Soil Conservation Services) method. Overall, computed discharge decreases as DEM resolution decreases with percentage varies between 0.98% to 1.76%. The biggest difference between DEM of 30 m and 8 m was shown by the Rational method. However, the difference between years is inconsistent with methods used with no significant pattern. Using the rational method, the biggest difference was by 18.73 m3/s, making up 1.76%. With SCS-CN, however, the biggest difference was 14 m3/s or 1.32% and the smallest was 0.98%. Validation with field measurement suggests that the 8-m DEM varies only 0.16% with actual discharge. Therefore, in the Kuranji catchment, the SCS method coupled with 8-m DEM was found to be accurate for the estimation of surface runoff.
Keywords: DEM, Land use, Runoff discharge.
Scope of the Article: Internet and Web Applications.