Hydrology function of green open space (case study on the mainland of Jakarta Capital City Province)

The increase of impermeable surface is inversely proportional to infiltration, thereby increasing flooding. The lack of study on the role of green open space (GOS) in Jakarta’s urban hydrology was identified as a critical factor that discounted the role, and the target of GOS in supporting urban sustainability has not been achieved in Jakarta. The aim of this study was to fill this research gap by analysing the potential of GOS in minimising runoff through optimisation of its function as a storage area for water reserves. Data analysis was done quantitatively using Horton, Thornthwaite–Mather and Ffolliot equations. Results showed that recharge and discharge areas play a critical role in determining optimal water reserve locations, and soil texture is an important indicator that affects runoff. In addition, the proportion of GOS (as indicated by its fulfilment target in urban planning) affected an area’s chances of inundation and flooding. This study concluded that the hydrological function of GOS could be optimised through the sponge city system with GOS and blue open space integration using bioretention.