Effectiveness of stormwater facilities to reduce surface runoff and peak flow at JIExpo Kemayoran using Site Evaluation Tools (SET)

The high rate of urbanization is one of the problems that has occurred in Jakarta as capital of Indonesia. The implication is the change in land use from pervious cover to impervious cover which have an impact on increasing stormwater runoff. Jakarta International Expo (JIExpo) is one of commercial complex in Central Jakarta. The complex covered area around 43.59 hectares and highly impervious (approximately 84 percent). This study simulating two stormwater facilities green roofs and permeable pavements, with total area to be converted aproximately 9.21 hectares (21 percent). The modelling run using Site Evaluation Tools (SET) Microsoft Excels spreadsheet to show the both of stormwater facilities effect on the surface runoff and peak flow. The results indicated that the techniques can be used to reduce runoff volume and peak flow. Per unit area, the green roofs better than permeable pavements at reducing the surface runoff evaporation and evapotranspiration. However, permeable pavements were better than green roofs at increasing infiltration. The simulation shows that by the combination of green roofs and porous pavement, the surface runoff can reduced by approximately 57%, the runoff volume can reduced by approximately 1.20% for 2-year daily rainfall, and the peak flow can reduced by approximately 50%. Overall, the SET is easy to use and useful for evaluating the effects of stormwater facilities.