Sediment from coastal erosion and various land-based activities can affect reef health by covering corals, blocking light, and inhibiting new coral settlement. This can lead to degradation of reef ecosystems. To quantify sedimentation, we modeled how much sediment was being transported into the nearshore marine environment around the Main Hawaiian Islands.
The annual amount of sediment (tons/yr) reaching the coast was calculated using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Sediment Delivery Ratio model for each of the eight main Hawaiian Islands. Sediment load is a function of land use and vegetation type, geology, soil characteristics, rainfall, slope, and hydrology. Only land areas that drain to a stream which reaches the coast and have a sediment supply were considered. The resulting sediment load at each point where a stream meets the coast was dispersed offshore using the Kernel Density tool in ArcGIS, resulting in a map of annual average sediment conditions offshore.