RUN OFF CAUSED BY HIGH RISE BUILDINGS AND ITS CONTROL, A RESEARCH IN EAST SURABAYA

Land use conversion took place a lot in Surabaya with the establishment of many buildings in the form of malls, settlements, apartments and others. The construction of high-rise buildings in Surabaya is very rapid. These high-rise buildings contribute greatly as a cause of inundation. High building walls will increase the volume of rainfall-runoff, according to the wall area and the rain height coefficient in accordance with the direction of the wind. The coefficients obtained from previous studies are CCn = 0.07 (North), CCs = 0.09 (South), CCe = 0.08 (East), and CCw = 0.08 (West). The expected rainfall calculated by the Log-Pearson type III method produces R1 = 71.94 mm, R2 = 103.66 mm and R5 = 146.32 mm for the rain pattern using an 8 hours pattern. Determination of reservoir dimensions is based on the volume calculated from the sum of the flat top area of the building plus the four sides of the outer wall as the inflow volume, reduced by reservoir with the 0.10 m x 0.10 m size outlet hole.