Automated Derivation of Fish Habitat, Geomorphic Units & Transition Zones from Topography (Invited)
Abstract
Despite the growing availability of high resolution topography and imagery in fluvial environments, a systematic and coherent framework for the automated derivation of geomorphic units from topography alone does not exist. Coherent morphometric models of hillslope and upland topography have been around for some time. However, in fluvial environments the topographic derivation of geomorphic units is complicated by the stage dependence of features as well as inconsistent nomenclature and definitions. Moreover, defining fish habitat and geomorphic units in the absence of full hydraulic model solutions remains a challenge. A new tiered classification of geomorphic/habitat units is presented in which the tiers are tied to specific geoprocessing steps that can be readily confirmed or validated with simple field observations. The four tiers are i) detrended stage relative to bankfull, ii) shape/type (e.g. convexities, concavities, planar features, margins), iii) position (e.g. bank-attached, mid-channel, channel spanning) and iv) specific morphology (e.g. diagonal bar, plunge pool, rapid). The cell-by-cell raster-based workflow involves deriving a suite of different evidence rasters from raw DEMs, and using transform functions to translate these evidence rasters into a priori and conditional probabilities. These probabilities are then combined using Bayes Theorem and for every category a probability that a given cell is each category is produced. To produce a mutually exclusive mapping of geomorphic units and habitat from this probabilistic representation, each category is thresholded at a confidence interval (e.g. 90% probability) and then transition zones between unit types emerge. These transition zones often are hot-spots of biotic activity and are also some of the most important zones from a geomorphic change perspective from repeat topographic surveys. Examples of application from a diverse array of habitats throughout the Columbia Basin will be highlighted where the workflow has been put to the test on over 500 sites from the CHaMP (Columbia Habitat Monitoring Program). The tools will be made available to the community through the River Bathymetry Toolkit.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMEP41E..03W
- Keywords:
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- 1856 HYDROLOGY River channels;
- 1819 HYDROLOGY Geographic Information Systems (GIS);
- 1855 HYDROLOGY Remote sensing;
- 1895 HYDROLOGY Instruments and techniques: monitoring