Flood Control (Risk) and Land Drainage Management
Flood control and land drainage management is different from other Council infrastructure asset management. Flood control and drainage is provided naturally by rivers and streams. Council’s flood control and drainage ‘assets’ are infrastructure that seeks to improve on what nature provides.
Options can exist for flood capacity to be enlarged by constructing a stopbank ‘asset’; or alternatively for the same objective to be achieved by deepening the river channel through a controlled gravel extraction strategy.
Another complication is that nature and natural rivers are constantly changing on an irregular basis. Erosion, sedimentation, climate change, growth of trees and aquatic vegetation are examples of natural processes that affect the performance of rivers, as well as irregular flood damage.
This leads to the situation that without the construction of any recognised assets Council can be expending funds on maintaining ‘natural’ rivers to the status quo by vegetation control and sediment excavation, and this expenditure is often irregular over time depending on weather conditions.
In some areas there is the unusual situation that without the construction of any recognised assets Council is expending funds on maintaining ‘natural’ rivers to the status quo by vegetation control and sediment excavation.
A major upgrade to the stormwater drainage infrastructure and stopbank is underway on Caseys Creek.
Rural drainage channel network - Wairau Floodplain.
Urban stormwater stream channels - Blenheim, Riverlands, Picton and Renwick.