Instream and riparian implications of weed cutting in a chalk river

Abstract

were monitored at a site on the River Lambourn (The CEH River Lambourn Observatory) and major instream and riparian impacts were observed. Measurements clearly demonstrated how weed cutting enhanced flood flow conveyance, reduced water levels (river and wetland), increased river velocities, and mobilised suspended sediment (with associated chemicals) and reduced the capacity for its retention within the river channel. Potential implications in relation to flood risk, water resources, downstream water quality, instream and riparian ecology, amenity value of the river, and wetland greenhouse gas emissions were considered. Provided the major influence of macrophytes on instream and riparian environments is fully understood then the manipulation of macrophytes represents an effective management tool that demonstrates the great potential of working with nature.

Long-term Holocene groundwater fluctuations in a chalk catchment: evidence from Rock-Eval pyrolysis of riparian peats

“…The river splits into anastomosing channels in two anthropogenically modified flood meadow areas at Welford and Boxford (Allen et al , ). The whole river is designated as a site of special scientific interest, as it is a classic example of a lowland chalk river (Old et al , ).…”

“…The study site (51.44°N, 1.38°W) is located at a conspicuous bend in the Lambourn valley just to the north of Boxford (Figure ). This Boxford site is a special area of conservation because of the habitat it provides for Desmoulins whorl snail ( Vertigo moulinsiana ) and is also as a site of special scientific interest because of its wetland habitats (Old et al , ). It has been the subject of much recent work aimed at understanding the functioning of the wetland (House et al , 2015a, b) which has included the installation of boreholes (Allen et al , ; Newell et al , ) and geophysical surveys, including electrical resistivity tomography (Chambers et al , ) and ground penetrating radar (Musgrave and Binley, ).…”

Geographically widespread 13C‐depletion of grazing caddis larvae: A third way of fuelling stream food webs?

“…Methane is therefore a pervasive potential basal resource in lotic food webs, particularly since it is so readily and efficiently transformed into microbial biomass (Shelley et al., ; Trimmer et al., ). The methane in these streams is likely to have come from a variety of sources, including groundwater aquifers linked to underlying ancient oil and gas reserves (Bell et al., ; Cramer, Poelchau, Gerling, Lopatin, & Littke, ) as well as more recent autochthonous methane produced by in situ anaerobic methanogenesis under macrophyte beds (Old et al., ; Sanders et al., ; Wilcock & Sorrell, ). This suggests that there may be considerable amounts of previously ignored forms of both new and old carbon cycling through riverine food webs, with potentially important implications for river ecosystems.…”

Modelling groundwater/surface water interaction in a managed riparian chalk valley wetland

“…There is some succession, with plant communities graded from swamp and fen dominated by reed sweet grass ( Glyceria maxima ) and lesser pond sedge ( Carex acutiformis ) in the north to remnants of the MG8 community in the south. Current management is confined to the river, where instream macrophyte growth is cut back periodically to maintain flood conveyance and lower water levels (Old et al ., ).…”