Journal of Hydrology (NZ) 49 (2): 79-98 2010 © New Zealand Hydrological Society (2010) The interaction of river engineering and geomorphology in the Lower Wairau River, Marlborough, New Zealand Kyle Christensen1 and Crile Doscher2 1 River Engineering Sector Leader, Pattle Delamore Partners, Wellington, New Zealand 2 Faculty of Environment, Society and Design, Lincoln University, Canterbury, New Zealand. Corresponding author:
[email protected] Abstract the different regimes are also examined, The Wairau River is one of the most along with their implications for sustainable engineered river systems in the Marlborough management decisions. region. Historical river control works, particularly the blocking of the Opawa Keywords Breach and the subsequent construction of Geomorphology; river engineering; suspended the Wairau Diversion, have had a significant sediment transport capacity; aggradation. impact on flow and sediment transport in the Lower Wairau. Currently, the Lower Wairau Introduction is aggrading as a result of an increase in An understanding of the geomorphic setting sediment concentration and a decrease in the of rivers and the effects of past river control duration for which flows exceed the critical works on their current morphology is needed threshold to keep sediment entrained. These to anticipate how proposed management changes are attributable to the substantial policies or engineering works will affect reduction in flow in the Lower Wairau that is current processes and the rivers’ sediment a result of over half the total Wairau flow now transport capacity and future morphology. passing down the Wairau Diversion. During Such an understanding can inform the choice the previous period, following the blocking of of management options to minimise the the Opawa Breach up until the construction of need for future remedial works.