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Investigating the sensitivity of river wetted habitat to changes in flow

Waterfall in small stream

The relationship between flow and ecological health is an indirect one. Individual species and ecological communities respond to physical variables such as flow velocity, wetted habitat area, depth, and stream power. However, these variables are related to flow and, due to the fact that it is more easily measured, flow has been treated as a variable which can support the determination of ecological status or, for heavily modified water bodies, ecological potential by the UK environment agencies. In order to ensure that using flow as a variable provides robust evidence to support ecological classification, it is necessary to improve our understanding of the relationship between flow and the physical variables to which ecology responds. This project will review current literature and analyse existing data to determine the sensitivity of wetted river channel habitats to changes in flow.

Project Objectives

  • Perform a review of literature and existing data surrounding how wetted habitat is currently calculated and sensitivity classes for the rate of change of wetted habitat with flow (e.g. high, medium, low sensitivity)
  • To develop a method for calculating wetted habitat which is consistent with the UKTAG guidance on flow releases required to meet good ecological potential
  • Perform an analysis of existing river channel transect data and flow data (held by CEH and the UK environment agencies) to calculate relevant statistics and determine relationships between various parameters (e.g. sensitivity and catchment size)
  • To provide recommendations on how a method could be used to help assess the likelihood that a proposed flow release would meet the conditions required to meet good ecological potential as set out in the UKTAG guidance