BR_C12.qxd 08/06/2006 16:29 Page 257 Braided river management: from assessment of river behaviour to improved sustainable development HERVÉ PIÉGAY*, GORDON GRANT†, FUTOSHI NAKAMURA‡ and NOEL TRUSTRUM§ *UMR 5600—CNRS, 18 rue Chevreul, 69362 Lyon, cedex 07, France (Email:
[email protected]) †USDA Forest Service, Corvallis, USA ‡University of Hokkaido, Japan §Institute of Geological and Natural Sciences, Lower Hatt, New Zealand ABSTRACT Braided rivers change their geometry so rapidly, thereby modifying their boundaries and flood- plains, that key management questions are difficult to resolve. This paper discusses aspects of braided channel evolution, considers management issues and problems posed by this evolution, and develops these ideas using several contrasting case studies drawn from around the world. In some cases, management is designed to reduce braiding activity because of economic considerations, a desire to reduce hazards, and an absence of ecological constraints. In other parts of the world, the eco- logical benefits of braided rivers are prompting scientists and managers to develop strategies to preserve and, in some cases, to restore them. Management strategies that have been proposed for controlling braided rivers include protecting the developed floodplain by engineered structures, mining gravel from braided channels, regulat- ing sediment from contributing tributaries, and afforesting the catchment. Conversely, braiding and its attendant benefits can be promoted by removing channel vegetation, increasing coarse sediment supply, promoting bank erosion, mitigating ecological disruption, and improving planning and devel- opment. These different examples show that there is no unique solution to managing braided rivers, but that management depends on the stage of geomorphological evolution of the river, ecological dynamics and concerns, and human needs and safety.