Geographers at the Environment Agency think that the properties in Uckfield High Street are protected for flood events up to a return period of 10% annual probability (one in ten years). This is below the minimum standard of protection that the government recommends for urban areas.
To predict future flooding, hydrologists use data from the nearest recording station at Isfield weir, about 3.5 km downstream of Uckfield. The weir at Isfield was specially constructed to measure river flows and recorded a flow of 132 m3/s on 12 October 2000. The flow at Uckfield was estimated by reducing the flow at Isfield in proportion to the reduction in the catchment area. At Uckfield there is about 87% of the flow at Isfield.
The flows recorded at Isfield over 40 years help hydrologists to estimate the probability of flood flows of different magnitudes at Uckfield.
Uckfield Case Study: What flood events are likely in the future?
However it is very difficult to estimate reliably the large floods that occur on average once in 100 or 200 years. Newspapers and other reports of flooding over the last 150 years have been used to try and compare the 2000 flood with other large floods since 1852.
This evidence suggests that the flood of 2000 might be expected on average once in around every 200 years, or put another way about a 0.5% chance of occurring in any year.
| Return Period (Years) | Flood Peak (m3/s) Uckfield |
| 5 | 44 |
| 10 | 56 |
| 25 | 74 |
| 50 | 87 |
| 100 | 100 |
| 200 | 115 |
However, most climate scientists consider that climate change is likely to lead to different patterns of rainfall over the UK, including more extreme weather such as the 2000 storm over Uckfield. So predicting future flood risk from past events may not be particularly reliable.
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