To adjust grid spacing or stream threshold

Identify smaller streams with more precision or analyze larger watersheds faster.

Watershed analysis identifies watersheds by sampling square grids of terrain. Grid Spacing and Stream Threshold correlate directly to the size of watersheds identified. Before starting watershed analysis, adjust Grid Spacing or Stream Threshold to identify smaller streams with more precision or analyze larger watersheds faster.

Click Analyze Drainage (Watershed).

Adjust the Grid Spacing or Stream Threshold controls in the Analysis Settings section of the Create Watershed panel.

Analysis Settings

Setting	Notes
Grid Spacing	Controls the size of the square grids sampled for streams. Adjusting the value to sample smaller grid squares helps identify small tributaries but requires more analysis. For example, adjusting to 15m x 15m squares from default 30m x 30m squares results in an analysis 4x larger. Raising the values finds larger streams and larger watersheds faster but may miss smaller ones.
Stream Threshold	Sets the number of grid cells used to define streams. Adjusting the value to a lower setting identifies smaller streams. For example, a stream threshold of 100 indicates that a stream is created once there are a minimum of 100 upstream grid squares flowing into a stream's starting point. Set to 100, a stream is created when at least 90,000 square meters are upstream of the starting point: 30m x 30m x 100.

Setting

Notes

Grid Spacing

Controls the size of the square grids sampled for streams. Adjusting the value to sample smaller grid squares helps identify small tributaries but requires more analysis. For example, adjusting to 15m x 15m squares from default 30m x 30m squares results in an analysis 4x larger. Raising the values finds larger streams and larger watersheds faster but may miss smaller ones.

Stream Threshold

Sets the number of grid cells used to define streams. Adjusting the value to a lower setting identifies smaller streams. For example, a stream threshold of 100 indicates that a stream is created once there are a minimum of 100 upstream grid squares flowing into a stream's starting point. Set to 100, a stream is created when at least 90,000 square meters are upstream of the starting point: 30m x 30m x 100.