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Regional variations in the sediment structure of trout streams in southern England: benchmark data for siltation assessment and restoration
Author(s) -
Milan D.J.,
Petts G.E.,
Sambrook H.
Publication year - 2000
Publication title -
aquatic conservation: marine and freshwater ecosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.95
H-Index - 77
eISSN - 1099-0755
pISSN - 1052-7613
DOI - 10.1002/1099-0755(200011/12)10:6<407::aid-aqc421>3.0.co;2-4
Subject(s) - geology , silt , salmo , sediment , siltation , trout , streams , hydrology (agriculture) , electrofishing , tributary , geomorphology , fish <actinopterygii> , geotechnical engineering , fishery , geography , computer network , cartography , computer science , biology
1. 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). 2. 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. 3. 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). 4. 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). 5. 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. Copyright © 2000 John Wiley & Sons, Ltd.