ISIS Results Help Reshape UK Flood Maps

Cost-effective integrated software solutions.

The major flood events of 2007 not only caused widespread destruction across many towns, villages and rural areas in the UK, but also lead to the Environment Agency refining the country’s Flood Map. Whilst this has highlighted areas that now require better flood management it also brings areas of land into flood risk zones that had no record of previous flooding.

The new flood maps can have a serious impact on the cost of insurance and can hinder new development. However, these flood maps can be challenged and, in the case of Staveley Works near Chesterfield, they were challenged successfully by the environmental consultants Enzygo. This has now led to the local Council adjusting its long term vision for the site, thereby providing a real chance of development in due course.

The starting point for Enzygo was to establish what evidence was provided by the Environment Agency to determine that the majority of the site was at medium risk of flooding. It was quickly discovered that the ruling had been derived from aerial photography, taken of the site following the flooding event in the summer of 2007, although on closer inspection the accuracy of the imagery was deemed to be poor.

More importantly, it was agreed with the Environment Agency that, in principle, most of the site should not be considered to have flooded from the neighbouring River Rother during the summer of 2007 and therefore should not be shown as part of Flood Zone 2 on the Flood Map. However, it was agreed that the Flood Map could only be amended following further hydraulic modelling of the river and submission of digital copies of the site’s topographic survey.

Enzygo re-ran the Environment Agency’s ISIS hydraulic model of the River Rother, which runs through the area, together with detailed topographic survey information of the site. The outcome confirmed that the majority of the site should now be currently designated within Flood Zone 1.

ISIS allows consultants like Enzygo to carry out fast and accurate modelling of the key elements of river and channel systems. It includes full solution modelling of open channels, floodplains, embankments and hydraulic structures. Any hydrological method can be used and rainfall-runoff simulation enables both event based and conceptual hydrological methods…

Read the full article from CH2M HILL