Flood exposure is one of the most important factors in the field of flood risk assessment. With climate change expected to intensify extreme precipitation and increase mean sea level in the future, it is imperative to evaluate how flood exposure in terms of affected population will increase. The main gap aimed to be filled by this research is the consideration of flood exposure in return period-based flood risk assessments as it is often neglected in existing studies that developed flood risk curves which are only focused with economic damages. With a calibrated and validated Rainfall-Runoff-Inundation (RRI) model that was set up for the Pasig-Marikina-Laguna Lake Basin in the Philippines, return period-based simulations were con- ducted. Rainfall volumes were derived by frequency analysis on dynamically downscaled MRI-AGCM 3.2S and 3.2H past and future (RCP2.6 and RCP8.5) climate scenarios. Of all scenarios, MRI-AGCM 3.2S RCP8.5 for 3-day storm yielded the largest flood extents and exposure. Rainfall volumes, flood extents, and average lake levels increased with increasing return period. Results show that lake level rise ranged from 0.02 m (2-yr) to 1.56 m (400-yr). Flood extents and exposure were analyzed by developing flood extent and flood exposure curves, respectively, revealing that flood extents can increase up to around 3 times, while flood exposure can increase up to 13 times in the far future, depending on the return period. Flood exposure also increased both due to the increased hazards and population growth, assuming constant spatial distribution. These findings can help policymakers improve their flood management strategies for combatting climate change impact in the future.
SERRANO et al. (Thu,) studied this question.