Physical controls on the diversity and distribution of river channel habitats
thesisposted on 2014-12-15, 10:33 authored by Joanna Lynn. Kemp
This study investigated the relationship between in-channel physical conditions and the diversity and distribution of macroinvertebrate habitats, known as 'functional habitats'. The Welland, Nene, Ouse and Deben catchments, in the English lowlands, were studied during the summer months of 1995 and 1996.;The physical conditions, in terms of depth, velocity and Froude number, associated with each of the functional habitats were identified.;The relationship between functional habitat diversity and the in-stream physical environment was examined at two levels: the cross-section and the 50 m reach.;Habitat diversity in a cross-section was highest in 'riffle-like' as opposed to 'pool-like' conditions. Cross sections with a high coefficient of Froude number variation were also associated with high habitat diversity. No strong seasonal trends were observed, from early to late summer, in either physical variables, functional habitat diversity or habitat abundance (except for a small change in velocity).;Habitat diversity in a reach was highest when the river was found to have a 'natural' channel width and was reduced if the river deviated greatly from its 'natural' (predicted) width. Two types of physical channel degradation led to the river being wider that predicted. These were 'over-widening' and 'ponding'. Sites with these conditions contained a characteristic functional habitat frequently; over-widened reaches were dominated by 'silt' and 'emergent macrophytes' while ponded reaches were dominated by 'floating-leaved macrophytes' and 'macroalgae'.;Functional habitat diversity was positively related to spatial heterogeneity at the reach scale. It was highest where 65% of the reach was less than 40 cm deep, and lowest when the reach was uniformly shallow or deep.
Date of award1999-01-01
Awarding institutionUniversity of Leicester