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Valley Bottom

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Summary

Extract valley bottom from a DEM and a stream network.

Tags:
hydrography, spatial components, valley bottom, detrend, relative, dem, alluvial floodplain, stream network

Usage

Within a watershed, extraction of a valley bottom related to a hydrographic network is a crucial step for the fluvial corridor characterization. Defined as the modern alluvial floodplain (Alber & Piégay, 2011)1, valley bottom is the deposition zone of alluvium since Holocene (Gregory, 1979)2 and includes both riverbed and floodplain. This valley bottom crucial fluvial unit with important water, material and biota transfers (Nanson & Croke, 1992)3. Valley corridor width also controls fluvial dynamics and patterns so that extracting this layer is often a preliminary step in the biogeomorphic characterization of stream networks (Notebaert & Piégay, 2013; Roux et al., 2014)45.

3 methods to detrend DEM are proposed:

  • Topological is identical to (Roux et al., 2014)5 and (Alber & Piégay, 2011)1.
  • Nearest is fast and helpful if your stream network does not match perfectly with your DEM.
  • Flow is slower, but precise. You may need to fill depressions of your DEM and resolve flat lands before trying to extract the valley bottom.

Valley Bottom

Parameters

Parameter Description Type
Input DEM
IN_DEM 		Input raw DEM coded on Float32 Default value: [3] RasterLayer
Input stream network
IN_STREAM 		Input stream network LineString
Detrending method
METHOD 		Detrending method (see documentation above) Default value: Topological Enum
Disaggregation step (topological detrending only)
STEP 		Distance of stream network segmentation Default value: 50.0 Number
Isolated objects aggregation distance
AGGREG 		Maximal distance to aggregate small parts of valley bottom extracted Default value: 5.0 Number
Max width (large buffer size)
BUFFER 		Size around the stream network in which the valley bottom will be researched Default value: 1500.0 Number
Minimum relative height value
THRESH_MIN 		Minimum elevation to extract from the Relative DEM Default value: -10.0 Number
Maximum relative height value
THRESH_MAX 		Maximum elevation to extract from the Relative DEM Default value: 10.0 Number
Simplify Valley Bottom tolerance
SIMPLIFY 		Simplification tolerance of the valley bottom polygon (in projection unit) Default value: 10 Number
Smooth Valley Bottom iterations
SMOOTH 		Smoothing iterations of the valley bottom polygon Default value: 5 Number
Output valley bottom
OUT_VB 		Output valley bottom polygon Polygon

See Also

  1. Alber, A., & Piégay, H. (2011). Spatial Disaggregation and Aggregation Procedures for Characterizing Fluvial Features at the Network-Scale: Application to the Rhône Basin (France). Geomorphology, 125(3), 343–360. https://doi.org/10.1016/j.geomorph.2010.09.009 ↩↩

  2. Gregory, K. J. (1979). The fluvial system, S. A. Schumm, New York, Wiley, 1977. No. of Pages: 338. price: £16.50. Earth Surface Processes, 4(1), 97–98. https://doi.org/10.1002/esp.3290040121 ↩

  3. Nanson, G., & Croke, J. C. (1992). A genetic classification of floodplains. https://ro.uow.edu.au/articles/journal\contribution/A\genetic\classification\of\floodplains/27708159 ↩

  4. Notebaert, B., & Piégay, H. (2013). Multi-scale factors controlling the pattern of floodplain width at a network scale: The case of the Rhône basin, France. Geomorphology, 200, 155–171. https://doi.org/10.1016/j.geomorph.2013.03.014 ↩

  5. Roux, C., Alber, A., Bertrand, M., Vaudor, L., & Piégay, H. (2014). “FluvialCorridor”: A new ArcGIS toolbox package for multiscale riverscape exploration. Geomorphology. https://doi.org/10.1016/j.geomorph.2014.04.018 ↩↩