Maximum branch length (`Bmax`) is the longest branch length between a grid cell's flowpath and the flowpaths initiated at each of its neighbours. It can be conceptualized as the downslope distance that a volume of water that is split into two portions by a drainage divide would travel before reuniting.

If the two flowpaths of neighbouring grid cells do not intersect, `Bmax` is simply the flowpath length from the starting cell to its terminus at the edge of the grid or a cell with undefined flow direction (i.e. a pit cell either in a topographic depression or at the edge of a major body of water).

The pattern of `Bmax` derived from a DEM should be familiar to anyone who has interpreted upslope contributing area images. In fact, `Bmax` can be thought of as the complement of upslope contributing area. Whereas contributing area is greatest along valley bottoms and lowest at drainage divides, `Bmax` is greatest at divides and lowest along channels. The two topographic attributes are also distinguished by their units of measurements; `Bmax` is a length rather than an area. The presence of a major drainage divide between neighbouring grid cells is apparent in a `Bmax` image as a linear feature, often two grid cells wide, of relatively high values. This property makes `Bmax` a useful land surface parameter for mapping ridges and divides.

`Bmax` is useful in the study of landscape structure, particularly with respect to drainage patterns. The index gives the relative significance of a specific location along a divide, with respect to the dispersion of materials across the landscape, in much the same way that stream ordering can be used to assess stream size.

## See Also

flow_length_diff

## Reference

Lindsay JB, Seibert J. 2013. Measuring the significance of a divide to local drainage patterns. International Journal of Geographical Information Science, 27: 1453-1468. DOI: 10.1080/13658816.2012.705289

## Function Signature

`def max_branch_length(self, dem: Raster, log_transform: bool = False) -> Raster: ...`

## Project Links

WbW Homepage User Manual Support WbW