GIS catchment delineation (legacy ArcGIS)

Legacy HDAT depended on ArcGIS/ArcHydro toolbox automation to derive catchment properties used by hydrology (area, flowpath length, slope proxies, etc.).

Legacy ArcHydro stage sequence (observed)

1. Fill sinks
2. Flow direction
3. Flow accumulation
4. Stream definition (threshold)
5. Stream segmentation
6. Catchment grid delineation
7. Catchment polygon processing
8. Drainage line processing
9. Adjoint catchment
10. Batch pour points + watershed/subwatershed delineation
11. Longest flow path extraction
12. 3D line construction
13. Flowpath metric derivation (lengths, elevations, slopes)
14. Export shapefiles and Excel results

Typical derived metrics used by HDAT hydrology

• catchment area
• longest flowpath 2D/3D lengths
• upstream/downstream elevation
• slope proxy (e.g., slope between 10% and 85% points)

Outputs (legacy)

• layers: Catchment, DrainageLine, AdjointCatchment, Watershed/Subwatershed, LongestFlowPath, Line3D
• Excel: “Catchment Delineation Results.xlsx” and flowpath profile worksheets (distance vs elevation)