TITLE:
Oxbow Lakes as Geological Archives of Historical Changes in Channel Substrate, Swan Creek, Toledo, Ohio (USA)
AUTHORS:
Jocelyn L. Hicks, James E. Evans
KEYWORDS:
Oxbows, Channel Substrate, Legacy Sediment, Anthropogenic Change, Sediment Budget
JOURNAL NAME:
Open Journal of Modern Hydrology,
Vol.12 No.2,
March
15,
2022
ABSTRACT: Efforts to restore urban rivers require an
understanding of human-influenced changes in channel substrates. This study
uses three naturally-occurring oxbows in a 3.5 km reach of Swan Creek, flowing
through the City of Toledo, Ohio (USA) to reconstruct historical changes in
channel substrate. Human impacts in the watershed were: 1) land clearance for
agriculture (peaking in 1900-1920) and for suburban housing tracts (peaking in
1945-1970), followed by 2) the post-1940 creation of more efficient urban
run-off systems from streets, parking lots, housing developments, and shopping
centers. Historical aerial photographs and maps from 1935, 1940, 1950, 1963,
1974, and 1994 were georeferenced using ground control points, input to ArcGIS,
and have root mean square error (RMSE) ranging from 0.19 - 0.77 m (average RMSE
= 0.47 ± 0.20 m) when compared to the 2006 digital ortho quarter-quadrangle
(DOQQ) image used as the basis for comparison. Results showed that channel
sinuosity continually increased from 1.88 (1935) to 1.99 (2006). Two oxbows
probably formed in 1913, and the third formed in 1940. Sediment cores and
trenches were used to recognize historical channel substrates. Age control was
provided by 14C geochronology and labels on food packaging materials
found in flood layers. Grain-size analysis of channel substrates shows a
historical coarsening-upward trend: the largest clast size interval (f5) changes from +0.78f in pre-1935 channels, to －1.15f in pre-1940 channels, to －1.69f in the 2006 channel. These results indicate recent urban runoff created fluvial pavements and
increasing channel mobility as the stream removes legacy sediment from
intrabasinal sediment storage.