How interactions between fluvial processes and large wood structure forested river corridors
Abstract
Interactions between lateral channel mobility and transport and deposition of large wood create spatially heterogeneous floodplains, which can influence geomorphic and ecological characteristics of river corridors. We investigate the patterns of LW in five floodplains in northwestern Montana using imagery available in Google Earth and field measurements. We determined river characteristics and the amount of downed wood in the channel and floodplain in continuous 500-m segments in reaches of the Swan River (drainage area (DA): 1680 km2), and Ole (DA: 131 km2), Park (DA: 112 km2), Coal (DA: 157 km2), and Nyack Creeks (DA: 236 km2). Sites include unmanaged floodplains and floodplains that have been logged, but wood is not actively removed from the channels. Field work was conducted on a randomly selected subset of reaches to determine the accuracy of wood measurements using Google Earth imagery, particularly with respect to downed wood under the floodplain canopy cover. River characteristics included in statistical analyses are planform, channel and valley width, drainage area, gradient, sinuosity, number of active, secondary, and abandoned channels, and number of bars. LW characteristics include the number of individual pieces and wood accumulations, the geomorphic location of wood (e.g., bar/island, channel vs. floodplain, abandoned channel), and the proportion of pieces in jams. Within the active channel, bars and islands preferentially store LW compared to other geomorphic locations. Within the floodplain, LW is preferentially stored in abandoned channels. Straight reaches have substantially lower wood loads in channels and floodplains than the other planform types, despite comparable ratios of valley/channel width. The results provide insight into how fluvial processes govern the abundance and spatial distribution of LW within the river corridor, which has implications for the abundance and distribution of organic carbon in LW, habitat diversity, and nutrient dynamics. Human modification of river channels and floodplains, such as removal of LW and the alteration of water and sediment fluxes, can change multiple aspects of process and form within the river corridor.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMEP33F..07L
- Keywords:
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- 1813 Eco-hydrology;
- HYDROLOGY;
- 1820 Floodplain dynamics;
- HYDROLOGY;
- 1824 Geomorphology: general;
- HYDROLOGY;
- 1862 Sediment transport;
- HYDROLOGY