Delivering flood protection

Greater Wellington's Flood Protection officers work to protect the region's communities from the hazards and consequences of flooding. The methods used fall into two broad categories, structural and non-structural.

Structural methods

Structural methods are physical works such as stopbanks, or rock rip-rap and vegetation placed to protect river edges. These methods are designed to keep the river in its channel, or river corridor, and away from populated areas and valuable community assets.

• Stopbanks to contain the river when it is in flood.
• Berm and bank edge protection works to protect river berms and stopbanks from erosion. Having built a barrier to keep the river out we don't want the river to wash it away, so river banks are strengthened with rock or vegetation.
• Gravel management, such as taking gravel out of the river bed to maintain the channel capacity.
• River alignment control - to keep a river on a designed course.

Structural methods will provide varying degrees of physical protection against flooding, but they are not completely failsafe. In very large floods they cannot be relied on. The larger the flood, the greater the risk of structural failure. This risk is known as residual risk, and is provided for by non-structural measures.

Non-structural methods

Non-structural methods deal with the risk of flooding by improving community resilience against the flood hazard and helping people to avoid flooding hazards. These methods encourage property owners to take responsibility for lessening personal effects of flooding.

• Encouraging appropriate land-use in flood-prone areas through rules in district plans that deal with construction and earthworks in these areas. This may include using floodable areas as sports fields or car parks.
• Raising community awareness of the risks and realities of living on a floodplain.
• Encouraging emergency preparedness in the community, and providing flood warnings.
• House-raising and flood-proofing of at-risk properties.
• Catchment management such as reforestation to reduce rain run-off.

Recent research has shown that in many cases, costly structural methods such as stopbanks have not significantly reduced potential flood damage because additional development has continued in flood-prone areas. Where appropriate, we will encourage non-structural methods of protection.