Feature lifespan and design assessment

• Introduction to lifespan and design mapping
• Quick GUIde to lifespan and design maps
• Parameter hypotheses
• River design and restoration features
• Code extension and modification

Parameter hypotheses

Combinations of recurring parameters determine the lifespans of features. The code analyses the following parameters, where the application order (hierarchy) differs from the alphabetic order for reasons of map integrity (see coding conventions in the Signposts). Calculation details are provided within the descriptions for defining threshold values.

• chsi composite Habitat Suitability Index (dimensionless value between 0 and 1)

• d2w is the surface depth to the groundwater table (length units)

• det is the detrended DEM (length units)

• Dcr are mobile or stable grain sizes that are entrained by (non-frequent) discharges that occur according to a defined return period (see angular boulders)

• fill corresponds to annual sediment deposition rates (length units; see also Wyrick and Pasternack 2016)

• Fr is the Froude number (dimensionless hydraulic variable) corresponding to u/(h g), where g denotes gravity acceleration

• h is the flow depth (length units)

• mu are the morphological units (strings; see also Wyrick and Pasternack 2014)

• Se is the energy slope (dimensionless hydraulic variable; cf. angular boulders and side channels sections)

• scour corresponds to annual erosion rates (length units, see alsoWyrick and Pasternack 2016)

• sidech delineation of priority regions for side channels (Van Denderen et al. 2017)

• taux (or τ_*) is the dimensionless bed shear stress and its critical value τ_{*, cr} (–)

• tcd combines scour and fill analysis

• u is the flow velocity (length per time: fps or m/s)

• wild wildcard parameter that can only take on/off values (noData, 0 or 1)

The code uses the mu raster to identify feature-adequate morphological units that are stored a feature.mu_good list and feature-inadequate units that are stored in a feature.mu_bad list. Thus, two approaches are possible: an inclusive approach that limits relevant areas using the feature.mu_good list and an exclusive approach that excludes non-relevant areas using the feature.mu_bad list. The following morphological units are considered Wyrick and Pasternack (2014):