Towards holistic braided river management: The interface of geomorphology, hydrology, ecology and economics

Abstract

Braided rivers are some of the most dynamic and complex river systems in the world. They provide unique habitat to rare species, supply natural resources, and act as a source of groundwater recharge. However, they can also pose significant flooding and erosion hazards. Current management of braided rivers in Aotearoa New Zealand faces a strong need to balance competing values and interests. In this research, we explore the hydrological and ecological benefits of changing river bed levels and widths in the main groundwater recharge reaches of two braided rivers, and assess the market and non-market costs and benefits associated with those changes to explore alternative management approaches. Theoretical width and bed level scenarios were developed for two case study reaches: the Ngaruroro River (Hawke's Bay region) and the Wairau River (Marlborough region). This study indicates, in general, that widening braided rivers has benefits for aquatic ecology and groundwater recharge, and that lowering bed levels can have costly impacts on ecology and groundwater that exceed economic benefits associated with aggregate extraction. This study contributes to the growing body of research aiming to quantify possible economic benefits of alternative river management and restoration approaches.