# terrain-hydrology

> Claude/Codex skill by [@muend](https://omgskills.com/library/muend/index.md) · 35 stars · Updated 2026-10-17

Always invoke for terrain, drainage, viewshed, or visibility analysis from elevation, even before the DEM or correct surface is chosen. Covers DTM-versus-DSM selection, slope, aspect, curvature, hillshade, conditioning, flow direction/accumulation, streams, watersheds, and catchments. Use point-cloud-lidar first only when an elevation surface must be created from LiDAR or photogrammetric points.

Tags: agent-skills, ai, ai-agents, claude-code, codex, geoai, geospatial, gis, github-copilot, google-earth-engine, lidar, machine-learning, postgis, remote-sensing, spatial-analysis, spatial-data-science

## Install

```sh
git clone https://github.com/muend/geoai-skills /tmp/geoai-skills && ln -s /tmp/geoai-skills/skills/terrain-hydrology ~/.claude/skills/terrain-hydrology
```

## From README

Terrain & Hydrology Purpose: terrain products whose numbers are physically meaningful. The two recurring failure modes: unit mismatch (degree coordinates with meter elevations silently corrupts every derivative) and unconditioned DEMs (flow routed into spurious pits produces fragmented, fictional streams). DEM hygiene first | Check | Rule | |---|---| | Surface type | DTM (bare earth) for hydrology/slope; DSM (with canopy/buildings) for viewshed/solar. Using a DSM for watersheds routes rivers over treetops. | | Source | Copernicus GLO-30 \> SRTM for most global work; national LiDAR DTMs when available (see point-cloud-lidar to make your own). Record source + acquisition date. | | Nodata | Identify the nodata value (-9999, -32768, 3.4e38) and mask it — never let it enter statistics or fill algorithms as "very deep hole". | | Voids | Fill data voids (interpolation from edges) BEFORE hydrological conditioning; document filled areas.

## Links

- HTML page: https://omgskills.com/library/muend/geoai-skills/skills/terrain-hydrology/
- GitHub: https://github.com/muend/geoai-skills
- Author: [@muend](https://omgskills.com/library/muend/index.md)

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