STUDI EVALUASI DRAINASE (STUDI KASUS: KELURAHAN TUNGGUL WULUNG, KECAMATAN LOWOKWARU, KOTA MALANG)

Changes in land use in Malang City affect the soil's ability to absorb water. This is supported by the growth in population in Malang City which continues to increase every year. If there is high intensity rain, it will result in flooding at several points. To analyze the feasibility of existing drainage using rain data from the nearest station, namely the East Java Climatology Station ID WMO 96943 Karangploso. Data is processed using the Type III Log Person Method with a return period of 2 years. Then the Smirnov Kolmogrov test was carried out to determine the difference between empirical and theoretical probabilities with the result Dmax = 0.202 < Dcr = 0.41, so the distribution was accepted. To determine the drainage coefficient value, it is planned based on the average value (C̅) in each section of the drainage area. In nggul Wulung Village itself there are 28 channels. To calculate the high population growth using data from 2012 – 2022. The population growth rate was 0.659%. Population growth in 2027 will be approximately 20,780 people. The estimated average water demand in the study location is 0.001157 liters/second/person for the medium city category. The duration of ground surface water flow to the nearest channel is calculated using a nomogram graph by taking into account the slope, coefficient, roughness and length of the channel. The design flood discharge calculation is calculated from the sum of Qah and Qak. We calculate the evaluation of existing channels from the latest available data. From the analysis that has been carried out, there are 5 channels that are not feasible. The alternative is to re-plan channels that are no longer feasible