Marlborough's Wairau River and its tributaries provide groundwater resources for agricultural and other uses on the Wairau floodplain, but also place Blenheim and its surrounding areas at risk of flood.
Flood control works have been part of local history for 100 years. The Marlborough District Council continues to upgrade and maintain these works. The Wairau floodplain is stopbanked to prevent floodwaters breaking out on to it. The Omaka, Ōpaoa and Taylor Rivers are also stopbanked.
A flood from these rivers is rated as having less than a 10% chance of breaking out of the floodways within the next 10 years, ie; one flood in 100 years. Associated with the flood control works are extensive drainage works for Blenheim and for much of the low-lying land to its east that is less than 3 m above sea level. Flood control works for the Waitohi and Waikawa Streams through urban Picton are to a similar high standard.
Elsewhere in Marlborough, flooding is either much less an issue or it is uneconomic to carry out flood control work. River works outside the Wairau floodplain area are, therefore, on a lesser scale.
The map shows the major river systems in Marlborough: Te Hoiere/Pelorus, Wairau and Awatere.
Marlborough District Council has a major role in alleviating flood situations to reduce threat to life, damage to property, and to keep roads and other infrastructure operating.
Find information on river works data here.
Council has reviewed its gravel extraction policies in order to best manage its flood control objectives and maintain a supply of gravel to construction industries.