Investigating the sensitivity of river wetted habitat to changes in flow. Objective 3: Identification and analysis of wetted habitat sensitivity thresholds.

Laize, Cedric L.R.; Edwards, Francois K.. 2017 Investigating the sensitivity of river wetted habitat to changes in flow. Objective 3: Identification and analysis of wetted habitat sensitivity thresholds. Wallingford, NERC/Centre for Ecology & Hydrology, 42pp. (Report CRW2016-06, CEH Project no. C06108) (Unpublished)

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Abstract/Summary

This project aimed to improve the understanding of the response of river wetted habitat (represented by wetted perimeter WP) to change in flow (Q) in order to support ecological status and potential assessment in UK rivers impacted by abstraction/flow regulation, which is of high relevance to dam and hydropower scheme design. The analysis relied on a pool of >1,000 UK sites with good quality hydraulic data. A method to assess objectively WP sensitivity to Q was developed, which models WP as a function of Q in a consistent manner, then identifies three different sensitivity zones and corresponding flow thresholds mathematically (ranging from high sensitivity occurring at lower flows, medium sensitivity, and low sensitivity at higher flows). The study then investigated if wetted habitat sensitivity patterns could be related to catchment/river reach types. For c. two thirds of sites, WP was found highly sensitive to flow change at Q95 (5th percentile) or below, suggesting generic environmental flow values can mask variations in hydraulic sensitivity; there was no site featuring low WP sensitivity below Q95. Regarding typology, statistically significant patterns between sensitivity thresholds/ slopes and river types based on key catchment descriptors (area, altitude, permeability) were found; WP tend to be more sensitive to Q at higher flows for sites associated with smaller, lower elevation, and/or lower permeability catchments; sites with larger, higher elevation, and/or lower permeability catchments may feature sharper differences between sensitivity zones.

Item Type:	Publication - Report
UKCEH and CEH Sections/Science Areas:	Water Resources (Science Area 2017-)
Funders/Sponsors:	CREW
NORA Subject Terms:	Ecology and Environment Hydrology
Related URLs:	Funder/Sponsor
Date made live:	25 Mar 2019 11:37 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/522463

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