This project analyzes terrain-driven hydrologic behavior within the Ala Wai Watershed and Nuʻuanu Watershed to identify natural flow corridors and areas of concentrated drainage intensity. The objective was to evaluate how topography influences surface water movement and runoff convergence within two highly urbanized watersheds that directly impact downstream flood risk in Honolulu.

Digital Elevation Model (DEM) data was processed within ArcGIS Pro to derive terrain-based hydrologic variables. Preprocessing steps were applied to remove surface sinks and enforce continuous flow, ensuring that modeled drainage patterns accurately reflected real-world topographic controls rather than data artifacts.

Hydrologic modeling techniques were then used to generate flow direction and flow accumulation surfaces. Flow accumulation values were used as a proxy for drainage intensity, highlighting areas where surface runoff is most likely to converge and form preferential flow paths. These high-intensity zones represent natural drainage corridors that may correspond to stream channels, low-lying valleys, or urban conveyance pathways.

Watershed delineation was performed to separate the Ala Wai and Nuʻuanu drainage systems and analyze their flow characteristics independently. Resulting drainage intensity rasters were classified and symbolized using graduated color ramps to emphasize relative differences in flow concentration across each watershed.

The final map integrates terrain analysis with clear cartographic design, including hillshade enhancement, transparency blending, and consistent symbology to improve interpretability. This project demonstrates applied skills in terrain analysis, raster-based hydrologic modeling, quality control, and geospatial visualization, with direct relevance to flood risk assessment, watershed management, and urban stormwater planning—particularly for downstream areas such as Waikīkī.

This project identifies natural surface flow corridors to support watershed management, land-use planning, and infrastructure resilience. By mapping how water moves across the landscape under natural conditions, the analysis helps decision-makers understand flood pathways, erosion risk, and downstream impacts of development. The outputs can inform stormwater planning, conservation prioritization, and site design decisions by highlighting areas where altering natural flow may increase environmental or infrastructure risk.