# Fill Sinks (Wang & Liu)

Copyrights (c) 2007 by Volker Wichmann
This module uses an algorithm proposed by Wang & Liu to identify and fill surface depressions in digital elevation models.
The method was enhanced to allow the creation of hydrologic sound elevation models, i.e. not only to fill the depression(s) but also to preserve a downward slope along the flow path. If desired, this is accomplished by preserving a minimum slope gradient (and thus elevation difference) between cells.
This is the fully featured version of the module creating a depression less DEM, a flow path grid and a grid with watershed basins. If you encounter problems processing large data sets (e.g. LIDAR data) with this module try the basic version (Fill Sinks XXL).
References:
Wang, L. & H. Liu (2006): An efficient method for identifying and filling surface depressions in digital elevation models for hydrologic analysis and modelling. International Journal of Geographical Information Science, Vol. 20, No. 2: 193-213.

## Parameters

Grid system
Grid system
  Grid system
DEM
Input Grid
  Digital elevation model
Filled DEM
Output Grid
  Depression-free digital elevation model
Flow Directions
Output Grid
  Computed flow directions, 0=N, 1=NE, 2=E, ... 7=NW
Watershed Basins
Output Grid
  Delineated watershed basins
Minimum Slope [Degree]
Floating point
  Minimum slope gradient to preserve from cell to cell; with a value of zero sinks are filled up to the spill elevation (which results in flat areas). Unit [Degree]