River flow in Alpine environments is likely to be highly sensitive to
climate change because of the effects of warming upon snow and ice, and
hence the intra-annual distribution of river runoff. It is also likely
to be influenced strongly by human impacts both upon hydrology (e.g.
flow abstraction) and river regulation. This paper compares the river
flow and sediment flux of two Alpine drainage basins over the last 5 to
7 decades, one that is largely unimpacted by human activities, one
strongly impacted by flow abstraction for hydroelectricity. The analysis
shows that both river flow and sediment transport capacity are strongly
dependent upon the effects of temperature and precipitation availability
upon snow accumulation. As the latter tends to increase annual maximum
flows, and given the non-linear form of most sediment transport laws,
current warming trends may lead to increased sedimentation in Alpine
rivers. However, extension to a system impacted upon by flow abstraction
reveals the dominant effect that human activity can have upon river
sedimentation but also how human response to sediment management has
co-evolved with climate forcing to make disentangling the two very
difficult.