Alternatives of drainage engineering in tidal flood prone areas using eco-infrastructure approach in North Pekalongan

Abstract

Tidal flood is one of the the most persistent disaster in Indonesia. It often occurs during the high tide, which can be exacerbated by extreme tidal surges, land subsidence, and sea level rise. The coastal area of Pekalongan, especially in Panjang Wetan, is one of the impacted areas during the extreme tidal flood in May 2022. Data from Indonesia Geospatial Agency showed that maximum spring tides elevation reached + 0.4 to +0.5 m above the mean sea level. Currently, although sea dike has been installed in some parts, floods are still occurring. On the other hand, interest on the nature-based solution concept is globally increasing. Therefore, this study aimed to explore the possibility of eco-infrastructure applications in mitigating coastal flooding. The analysis was done through numerical simulation using HEC-RAS model which divided into three different scenarios: existing condition, grey infrastructure scenario, and a combination of grey and blue infrastructure scenario. The simulation results indicated that the existing drainage conditions in the area was not sufficient to accommodate the flood. The grey infrastructure could restrain the tidal overtopping, while the proposed eco-infrastructure could address this issue mainly by providing a buffer zone to prevent the water from entering the settlement areas.