Modeling Sediment Inputs to Maunalua Bay

Abstract

Mālama Maunalua identified polluted runoff and sediment as the number one threat to Maunalua Bay. Sediment is one of the primary land-based threats to corals and other marine organisms because it decreases light availability, smothers coral and alters habitats. Rain runoff transports sediment through streams and into the bay. In Maunalua Bay, runoff is high due to increased human populations and stream channelization. This stream channelization causes water to move downstream at a faster than normal rate and increases the amount of sediment. We review some options for homeowners to mitigate the amount of sediment reaching the streams. To create effective management solutions for sediment pollution in the bay, we modeled the current sediment exports. We analyzed the contributions of each watershed and correlations with land use type. We found that most sediment is retained in the upper part of the watershed in forested areas, and that most outputs come from Waialaenui and Wailupe. We suggest that any stream restoration activities should focus on the Waialaenui and Wailupe as this will have the most drastic effect on sediment loads.