River flooding is a significant hazard, being the most widespread and frequently occurring hazard within the Waikato region. Over time, many river systems within the region have been modified for the purposes of flood protection. River modification has:
While river modification has produced many benefits, it has not eliminated flood risks, and in some cases has encouraged the intensification of urban development within flood prone areas. River modification can also have significant adverse effects on natural river system characteristics, by altering the way in which rivers and flood plains would normally operate.
In recent years, issues such as population growth, land use change and the ever-increasing location of development within flood plains have compounded the risks associated with flooding. In addition, the frequency and intensity of extreme flood events appears to be increasing over time. This means that the provision of hazard information, land use policies and regulations, river and catchment management and related activities all need to be understood within the context of managing flood risks within a whole catchment.
As a result of the 2004 floods in the Manawatu-Wanganui and Bay of Plenty regions, the Government has recognised the importance of flood risk management to New Zealand. A significant amount of work has been completed by the Government, Local Government New Zealand and other key stakeholders to confirm national directions for flood risk management. As a result of this, national directions have become much clearer since 2004.
In order to achieve a reduction in the risks from flooding, all stakeholders, including district and regional councils, need to integrate their respective responsibilities under different pieces of legislation. This strategy intends to assist in this process.
Waikato Regional Council has a produced a strategy which provides guidance on how river flood risks will be managed across the region in the future. The strategy encourages better integration between the stakeholders involved in flood risk management and the work that the Waikato Regional Council does.
The way that rivers behave is not always easy to understand. Rivers transport large amounts of water and sediment and are continually changing. Sometimes these changes are natural due to the effects of weather an erosion and other times they are due to human intervention when land use changes or physical works are done on the river. By improving our understanding of how rivers behave we can start to think about how we can start to manage the flood risks.
River catchments can change naturally over long time periods but these changes can be accelerated by human intervention. Land use change, such as deforestation in the upper catchments of river systems can increase the quantity and speed of flood flows. By having fewer trees to intercept rainfall, more run off enters streams and rivers causing increased flows. As the rivers cross many council boundaries across the Waikato they can affect many communities during times of flooding.
The current flood risk management framework provides a sound basis for managing flood risks. In the future the framework will need to recognise and incorporte the principles of risk management into its decision making.
The Waikato has 20 major rivers and 1,400 streams. The shape of the land and the weather all play a part in increasing the risk of flooding. Communities in flood prone areas do not always understand the risks they are subject to and the strategy will try to improve the community understanding of the residual risks associated with flood protection or mitigation activities.
As severe weather events become more frequent and intense in the future river flood risks are also expected to increase. The impacts of such events may be amplified by land use changes, for example land clearance. Other factors to consider are how the predicted rises in sea level will impact on river flooding in coastal areas.
In 2005 the Government decided to review flood risk management in response to the major flood experienced across the Manawatu-Wanganui and Bay of Plenty regions. As a result of this there is now clear national direction on flood risk management.
Click here(external link) to find out more about the Flood Risk Management Review on the Ministry for the Environment website. You will also find other useful information on this website including:
The Flood Risk Management Strategy 2009 also sets out a regional framework that will be used to guide the management of river flood hazards. The framework is divided into the following parts:
The philosophy of the strategy is to develop an approach that recognises and allows for the nature and behaviour of river systems and puts in place a risk management framework that reduces river flood risks over time. The philosophy draws upon the results of the central government review of flood risk management and the New Zealand Standard for managing flood risk.
Waikato Regional Council is taking a leadership role in developing an implementing the regional flood risk management framework.
The vision for flood risk management within the Waikato region is outlined below.
Sustainable communities that:
There are two overall outcomes expected for river flood risk management in the Waikato region. It is expected that the regional river flood risk management framework will lead to the recognition and understanding of the nature and behaviour of river systems and a reduction in river flood risks.
The expected outcomes guide part 3 of the strategy - the Action Plan.
The purpose of the action plan is to identify actions which will assist in delivering the vision and outcomes. It identifies specific goals and actions required by Waikato Regional Council and partner organisations, communities and individuals in order to achieve the vision. It does tis by building upon Waikato Regional Council's exisiting work programme and directions, and identifying where new work may be required to help achieve the vision and outcomes. The action plan also outlines the areas of work where Waikato Regional Council wishes to work closely with the Territorial Authorities and other partner organisations to support the directions and expected outcomes of this strategy.
The work activities associated with river flood risk management can be broken down into five key work areas:
River Flood Risk Management Strategy 2009 (766kb PDF)