The character, volume and implications of sediment impounded in mill dams in Scotland: The case of the Baldernock Mill dam in East Dunbartonshire

Bishop, P., Muñoz-Salinas, E., MacKenzie, A.B., Pulford, I. and McKibbin, J. (2011) The character, volume and implications of sediment impounded in mill dams in Scotland: The case of the Baldernock Mill dam in East Dunbartonshire. Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 101(2), pp. 97-110. (doi: 10.1017/S1755691010009205)

Full text not currently available from Enlighten.

Publisher's URL: http://dx.doi.org/10.1017/S1755691010009205

Abstract

Reservoir sedimentation provides a valuable source of data on sediment flux. This paper assesses the record of sedimentation in the Baldernock Mill dam, a small mill dam in western Scotland. That record is based on the volume of sediment in the dam, and the detailed analysis of a continuously sampled stratigraphic section through the impounded sediment, with a chronology for mill dam construction and subsequent breaching based on historical maps and the impounded sediment’s content of <sup>137</sup>Cs and lead isotopes. The mill dam was constructed in c. 1820, was initially partially breached in the late nineteenth or early twentieth century and then fully breached by about the mid 1920s. The dam trapped relatively low volumes of sediment and the correspondingly low rate of sediment flux indicated by the volume of impounded sediment reflects the dam’s very low trap efficiency. The basal Unit 1 in the impounded sediments was deposited between dam construction and the initial breaching of the wall. The unit consists of repeated ‘triplets’ of a basal sand (flood deposit) grading upwards into a mud deposit (post-flood deposition), which is in turn overlain by an organic-rich layer of leaves and twigs (the subsequent autumn leaf fall). Unit 2 is similar to Unit 1 but lacks the organic layer, indicating the lack of ongoing standing water to trap the autumn leaf fall, and Unit 3 was deposited after full breaching of the wall. Mill dams in Scotland generally impound small steep bedrock channels – the latter reflecting a strong glacial legacy in Scotland – and are only small structures designed to ensure water for mills during dry periods in a climate of otherwise generally moderate to high and reliable rainfall. The small sizes of these dams and their low wall heights mean that they trap relatively low volumes of sediment that have minimal to minor downstream impacts if the dams fail.

Item Type:Articles
Keywords:Reservoir sedimentation, trap efficiency, channel adjustment, 137Cs, lead isotopes
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:MacKenzie, Professor Angus and Pulford, Dr Ian and Bishop, Professor Paul
Authors: Bishop, P., Muñoz-Salinas, E., MacKenzie, A.B., Pulford, I., and McKibbin, J.
Subjects:G Geography. Anthropology. Recreation > GB Physical geography
Q Science > QE Geology
College/School:College of Science and Engineering > School of Chemistry
College of Science and Engineering > School of Geographical and Earth Sciences
Journal Name:Earth and Environmental Science Transactions of the Royal Society of Edinburgh
ISSN:1755-6910
ISSN (Online):1755-6929
Published Online:11 February 2011

University Staff: Request a correction | Enlighten Editors: Update this record