Hydrologic response: Kaho'olawe, Hawaii

Kaho'olawe, the eighth largest island in the Hawaiian chain, has experience d major surface erosion during the last century due to overgrazing and mili tary activity. In this paper we report the results from a series of physica lly-based numerical simulations of hydrologic response to large rainfall ev ents, that were performed for Kaho'olawe. An event-based rainfall-runoff an d erosion model (i.e., KINEROS) was applied, in a geographic information sy stem (GIS) framework, to make quantitative and distributed estimates of inf iltration, Horton overland now generation, and erosion. A digital elevation model (DEM) was employed to delineate individual catchments across the isl and, and define areas of uniform slope within each catchment. A Landsat MSS scene of Kaho'olawe was used to classify the island into three distinct la ndcover categories via the normalized difference vegetation index (NDVI), T he landcover categories were then used to further approximate the spatial p attern of near-surface soil hydraulic properties across the island. Distrib uted estimates of saturated hydraulic conductivity and sorptivity were obta ined by ordinary kriging of 135 field measurements from the island. Sensiti vity analysis was performed to characterize what impart the uncertainty in soil-hydraulic property and rainfall data had on simulated runoff. Horton o verland now and the related transport limited erosion were shown to be high ly variable. The introduction of vegetation to denuded areas on Kaho'olawe was found to significantly reduce erosion.