Regional variations in the sediment structure of trout streams in southern England: benchmark data for siltation assessment and restoration
✍ Scribed by D.J. Milan; G.E. Petts; H. Sambrook
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 127 KB
- Volume
- 10
- Category
- Article
- ISSN
- 1052-7613
No coin nor oath required. For personal study only.
✦ Synopsis
Data are presented on the sedimentological characteristics of 51 river reaches which include trout (Salmo trutta) spawning grounds from three different hydrological regions of southern England: I, upland, hard-rock of the south west (20 sites); soft-rock of the east with, II, chalk (11 sites) and III, sandstone or limestone (20 sites).
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Data were obtained using a standard sampling protocol: at each site, five randomly distributed freeze-cores to a depth of 30 cm were taken to yield a composite weight of at least 20 kg.
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All sites had a well-developed armour layer and at more than 70% of the sites the armour layer had a median b-axis of more than 35 mm and included some cobbles (stones larger than 64 mm).
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The substratum at 65% of the Type I sites had less than 10% finer than 1 mm contrasting with all sites of Type II having more than 25% sub-1 mm. The Type II sites contained high levels of sands (0.125-1 mm). Type III sites had a wide range of fine sediments (15 -53% sub-1 mm) but were characterized by relatively high silt-clay contents (sub-0.063 mm) which exceeded 10% of the sample weights at six sites. At most sites, lower (15 -30 cm) sections contained about twice the loading of fine sediments compared with the surface layer (0 -15 cm).
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A target loading for the substratum of a healthy stream of the important sub-1 mm size fraction is set at 14%. Benchmark particle-size distributions for trout streams in (a) upland and (b) lowland areas are presented for use in assessing levels of siltation and in channel restoration in southern England.