Algorithm Details

This section provides in-depth documentation of the algorithms implemented in Overflow. Each page covers the mathematical foundations, data structures, and implementation details for a specific hydrological processing step.

Terrain Conditioning

Prepare raw DEMs for hydrological analysis by removing artificial depressions:

• Breach Algorithm - Remove depressions by carving least-cost flow paths
• Fill Algorithm - Fill depressions using priority-flood

Flow Routing

Determine how water moves across the terrain:

• Flow Direction - Compute D8 flow directions
• Flat Resolution - Resolve undefined flow in flat regions
• Flow Accumulation - Calculate upstream contributing area

Feature Extraction

Derive hydrographic features from the flow network:

• Stream Extraction - Extract stream networks from flow accumulation
• Basin Delineation - Delineate drainage basins
• Flow Length - Calculate upstream flow length and longest flow paths