This thesis focuses upon the sediment characteristics of salmonid spawning grounds in a
number of lowland and upland catchments in England and discusses the implications of
spatial and temporal variability of channel-bed sediment composition upon different stages of
the salmonid life-cycle. Substrate samples were obtained by using freeze-coring techniques,
thus avoiding the problems of elutriation of fine-sediments which have hindered many studies
in the past.
Spatial variability is assessed within-site, between-sites and between catchments. Temporal
development of channel-bed sediments is assessed both between and within spawning
seasons in two upland streams, one of which is regulated. Overall change in sediment quality
is demonstrated by changes in armour layer particle-size and variability in the fine-grained
sediment population. Vertical infiltration of fine-grained sediments was successfully
quantified by analysing core-section loadings over time. Results are explained in terms of
mechanisms and processes occurring at each scale.
A typology of streams has been developed based upon a continuum of granulometric
characteristics which ranged from coarse-grained upland sites to fine-grained (sandy) lowland
sites. Sediment quality of a number of lowland streams, based upon indices derived from the
literature, were classed as unsuitable by this methodology, largely because of the high
loadings of fine-grained sediments (in excess of 14% sub 1.0 mm material). As these streams
are known to support good salmonid populations, the usability of such indices is criticised. A
model is presented to predict percent weight fine-sediment (sub 1.0 mm) from maximum unit
stream power. Error margins limited this application however. The use of freeze-coring techniques for sediment quality assessment are discussed in the light of the results.
A Master's Thesis. Submitted in partial fulfilment of the requirements for the award of Master of Philosophy of Loughborough University.