Premium
Visual characterization technique for gravel‐cobble river bed surface sediments; validation and environmental applications Contribution to the programme of CIRSA (Centre Interuniversitaire de Recherche sur le Saumon Atlantique)
Author(s) -
Latulippe Christian,
Lapointe Michel F.,
Talbot Tracey
Publication year - 2001
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/1096-9837(200103)26:3<307::aid-esp160>3.0.co;2-r
Subject(s) - cobble , sampling (signal processing) , terrain , environmental science , hydrology (agriculture) , percentile , substrate (aquarium) , geology , statistics , geotechnical engineering , computer science , cartography , mathematics , habitat , geography , ecology , computer vision , oceanography , filter (signal processing) , biology
This paper presents an evaluation of the feasibility and the reliability of a visual characterization technique for gravel–cobble river bed surface substrate. Based on principal axis regressions, using phi scale (ϕ), comparisons of visual estimation and grid sampling techniques show that useful predictive relations ( R 2 = 0·78–0·88) exist between visual estimates of the surface d 16 , d 50 and d 84 and estimates obtained for the same percentiles with the grid sampling technique. Comparisons of visual estimation and the surface‐bulk sampling technique also indicate a predictive relation ( R 2 = 0·70) between the d 50 of the two methods. Trained operators can visually estimate gravel–cobble bed surface d 16 to uncertainties of 41 per cent, d 50 to 15 per cent and d 84 to 11 per cent (for example, there is a 5·5 mm error on a d 84 size of 50 mm). Furthermore, evidence shows that if operators are properly trained, a calibration relation for each percentile can be applied independently of operators. This visual characterization allows effective detailed mapping of spatial patterns in substrate size distribution along extensive reaches of gravel‐bed rivers. The technique can be very useful in creating terrain models for various geomorphological, hydrological and biological applications such as the determination of entrainment thresholds, hydraulic roughness and substrate suitability for benthic insects or salmonid habitat. Copyright © 2001 John Wiley & Sons, Ltd.