Intensive field monitoring of a reach Of upland gravel-bed river
illustrates the temporal and spatial variability of in-channel
sedimentation. Over the six-year monitoring period, the mean bed level
in the channel has risen by 0.17 m with a maximum bed level rise of 0.5
m noted at one location over a five month winter period. These rapid
levels of aggradation have a profound impact on the number and duration
of overbank flows with flood frequency increasing on average 2.6 times
and overbank flow time increasing by 12.8 hours. This work raises the
profile of coarse sediment transfer in the design and operation of
river management, specifically engineering schemes. It emphasizes the
need for the implementation of strategic monitoring programmes before
engineering work occurs to identify zones where aggradation is likely
to be problematic. Exploration of the sediment supply and transfer
system can explain patterns of channel sedimentation. The complex
spatial, seasonal and annual variability in sediment Supply and
transfer raise uncertainties into the system's response to potential
changes in climate and land-use. Thus, there is a demand for schemes
that monitor coarse sediment transfer and channel response.