Potential impacts of flood risk with rising sea level in Macau: Dynamic simulation from historical Typhoon Mangkhut (2018)

Abstract

Defence engineering infrastructures reduce casualties and economic losses, and alleviate damage, and respond to climate-change exacerbated coastal flooding. This study quantitatively estimated the relative sea level rise (SLR) in the Pearl River Estuary and investigated the potential upper and lower bounds of the maximum inundation depths in Macau City induced by Typhoon Mangkhut (2018). Extreme tidal levels are assumed to be coincident with the pre-landfall hour of Mangkhut during its movement towards the coast. Under both SLR scenarios, inundations caused by astronomical tides indicate a significantly shortened return period of flood events with a rising sea level. The tidal barrier with a crest elevation designed according to Typhoon Hato (2017) can effectively protect the Inner Harbor region from flooding by astronomical tides or Mangkhut-like typhoons occurring at low tides; however this effectiveness is lost under high tides. The results indicate the dominant role of tidal timing at inundation depths, which is also influenced by modulated surge heights owing to nonlinear tide–wave–surge and SLR–surge interactions. In spite of decreased surges affected by SLR around Macau, proper engineering countermeasures should be planned to cope with severe inundation by compounding unfavorable factors.