Adaptive Rainwater Management on Coral Islands: Multi-Method Integrated Rapid Optimization of Bioretention Systems

Although tropical coral islands receive abundant annual precipitation, the heavy rainfall and the high porosity of coral sand lead to rapid rainwater loss, posing a severe challenge to water use, soil water retention, and plant growth. Traditional bioretention systems are not suitable for these unique conditions, and there is still no effective adaptive framework for designing specific coral island bioretention systems. This study provides an efficient multi-method framework for the bioretention systems on coral islands. A bioretention system with engineering feasibility is constructed by using coral sand as the main substrate and combining it with common fillers. Then, the Analytic Hierarchy Process (AHP) is adopted to determine the optimal combination. Subsequently, the model was combined with the response surface method to compare the performance of the bioretention systems under different design parameters and determine the optimal setting. Finally, by simulating the actual rainfall conditions on the island, the performance of the optimized bioretention systems during the dry and rainy seasons was evaluated. The results show that under heavy rainfall conditions, the reduction rate of the total runoff volume of the optimized system is 67.7%. It is superior to pure coral sand in rainwater interception, and the total suspended solids in the effluent are less than 4 mg/L. These findings provide valuable insights into the development of bioretention systems on coral islands and propose a methodological framework to assist in the rapid establishment of such systems in other areas.