In deciding the best ways in which we should manage river (fluvial) and surface water (pluvial) flood risk in Lowestoft now and in the future, we have assessed a long list of options. To date we have only looked at one rainfall scenario – that with a 1.3% or 1 in 75 chance of occurring in any one year. This gives us a guide as to which options might be worth considering further.
The risk of surface water flooding depends on a complex interaction between the quantity of rain, where it falls, the topography, the amount of permeable land and the drainage systems. One of the key ways to manage surface water flooding is to work with nature, increasing the area of permeable land and places where water can naturally be held or stored. This is known as Sustainable Drainage and is the strategic option being considered in all areas. The location of sustainable drainage options will be targeted within the zones that contribute to the flood risk and can include a wide range of different measures.
At this stage we are starting to consider which combination of sustainable drainage features are likely to be the most technically effective in reducing flood risk in each target zone. Whether these are taken forward will depend on the willingness of individuals and communities to accept them and whether these options can be delivered at a cost that reflects a benefits provided and also the availability of land to install such features.
Due to the recent flooding, which led us to undertake a detailed investigation into the way the stream and local drainage systems operate, we have more data about the area. This enabled us to consider a wider range of options to manage the flood risk along the Kirkley Stream. These are all based on the assumption that the stream is maintained in its current (May 2016) state. We know that keeping the stream clear of vegetation is important as one of the key factors that led to the flooding in July 2015 was blockages by vegetation and debris.
What criteria have been used to assess the strategic flood risk management solutions considered?
In assessing the possible options the following criteria have been used to decide which of those solutions offer the best ways in which we should manage flood risk in Lowestoft now and in the future:
Having explored individual options as described in the table above, few appear to merit progressing alone so we suggest exploring further a range of measures in combination including:
As well as further studying the technical aspects of these options, we will be looking at whether they provide benefits during more frequent and/or more extreme storms and whether the benefits they provide outweigh the costs of implementation. Our ability to deliver many of these options will depend on the availability of suitable land and landowners’ co-operation.
Please see the Lowestoft Flood Risk Management Strategy summary document for more information in the Latest News section of the website.