Action needed to help those at risk of flooding

Finding solutions for residents and property owners in flood-prone areas is crucial. PHOTO/FILE

The downpour that caused the most recent October floods again raises the question about what should be done to minimise the harm to homes and businesses for the future.

Severe flooding is still a real risk for those who live in the Whangaehu Valley. One of the first recorded floods was in 1897 and again more than 100 years later when the Whangaehu River burst its banks in 2004 and 2006. Whangaehu residents have been told they can expect severe flooding at least every 20 years or so. So finding solutions for the residents and property owners is crucial.

In 2007 Horizons Regional Council analysed three options in a Whangaehu flood-risk assessment report. Residents could relocate their homes to higher ground or raise their homes at least two metres above their present levels, or a stopbank could be built.

Relocating or raising the height of homes with the obvious associated costs is not financially achievable for families. Nor is selling their home or property, which is now associated with a flood zone.

Whangaehu Marae spent in excess of $120,000 on a concrete fence to prevent flood damage.

The Horizons report estimated the costs of building a stopbank 600m long and up to 2.1m high plus associated protections to be around $1million. While there is no guarantee of foolproof protection from larger floods or stopbank failures, this does not seem a logical enough reason not to pursue the stopbank option. Costs and risks of stopbanks bursting have not prevented stopbank flood protection going ahead on other rivers, including the Whanganui. For instance, as a result of the October floods, sandbags were used to support the stopbanks and to further minimise and reduce potential flooding of homes along Kowhai Park in Whanganui.

The damage by flooding is not just to homes. It is causing serious landslips, severe damage to roads and bridges and is affecting electricity and telephone services. Farmers have to move their stock as their paddocks temporarily turn into lakes.

The council needs to make a decision about whether it wants to assist the residents of Whangaehu to stay in the area or not. While stopbank upgrading is under way for the Whanganui River, including plans to strengthen stopbanks more permanently to provide up to 50 years protection, Whangaehu residents still have no better protection than they did after the floods of 2004 and 2006.

In 2011 GNS Science (the Institute of Geological and Nuclear Sciences) commissioned a significant research report entitled Flood Risk Management in New Zealand: Where are we and where are we going?, which analyses how prepared we are as a country to cope with floods.

One of the gaps they highlighted in the research indicated a need to develop and implement updated techniques that will determine the economic risk of river flood hazards that can be applied consistently regionally and nationally. The report highlighted that the nation's economic performance and community functioning remained at risk from flooding of major river systems. The impact of climate change on extreme rainfall duration and intensity was another issue raised in the report, as well as a need to gain a better understanding of socio-economic profiles, energy use and transport choices into the future - including how many people and what assets are at flood risk and into the future.

The report predicted the damage and disruption caused by flooding could be on par with that caused by the disastrous earthquake of 2010. These predictions should surely set off the warning bells to all our local authorities.