New Paper Published : Bedload transport: Are we doing restoration right in the face of alpine climate change?

Alpine landscapes are undergoing climate warming at a higher rate than other regions of the world. The current and future impacts of this warming on the cryosphere (snow and ice) and their implications for stream flows are now well known and there exist predictions of how snow, ice and river flows are likely to evolve in Alpine environments over the 21st century (e.g. [1, 2, 3]). There is no doubt that such changes will also impact bedload transport in Alpine streams. Bedload transport in many Alpine streams is, however, also impacted significantly by the direct effects of human activities such as hydropower and gravel extraction (e.g. [4, 5]). These direct effect have dominated the concerns of bedload management or river restoration over the last decade or more. It is therefore a logical question to ask whether or not river restoration projects and the bedload management policies thought necessary to support them needs to adapt in the face of climate change. The lead in time to many policy solutions for bedload management, especially those involving new infrastructure, is not negligible. Given the current rate of warming in Alpine environments, higher than many non-Alpine regions [6], climate change sensitive bedload management may already be needed. However, the target of river restoration should not be bedload transport itself but rather the societal ecosystem services that are sustained by the consequences of bedload transport. This may be in terms of the right level of sediment evacuation to stop bed level rise during a flood that can lead to catastrophic loss of property and even life; or the gravel sized sediment that spawning salmonids need during the late autumn of each year; as examples of a wider set of services that rivers provide. Simply developing a bedload management policy to be climate sensitive is not enough; the focus has to be on the consequences of such policy for erosion, deposition, grainsize, river morphodynamics etc. These need to be evaluated at the scale of a river basin and so also need to recognize the basic challenges posed by sediment continuity; a policy decision to increase or to decrease bedload transport locally will have downstream consequences that may be either positive or negative. Communities and ecosystems downstream, may have already become accustomed to a certain bedload transport regime and this further complicates the problem. In this paper, we seek to answer six broad questions that should be part of a sustainable bedload management policy in Alpine environments in the light of climate change:
I. What must we be capable of predicting?
II. Is there a bedload transport “hockey stick” in Alpine streams?
III. Can we predict bedload transport rates now with sufficient precision and accuracy for them to be usable in predictions of the future?
IV. How might bedload transport capacity change in the future in Alpine basins?
V. How might sediment supply change in the future in Alpine basins?
VI. So, are we doing restoration right in the light of Alpine climate change?

A copy of the paper can be freely downloaded here.