Strategic Flood Risk Assessment

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Object

Evidence Base

Representation ID: 16368

Received: 25/04/2018

Respondent: Colney Parish Council

Representation:

Strategic Flood Risk
The Strategic Flood Risk Assessment (SFRA), published in November 2017, provides a detailed methodology for examining various flood factors which planning authorities and developers must take into account when planning applications are proposed (pp. 95-7).

The GNLP seeks to create a mass of new developments; many of these will be in the catchment areas of major rivers, including the Yare and Wensum. Such developments will affect natural drainage to rivers. In the Plan there is no specific commitment to natural processes of flood management which are highlighted in the SFRA.We support the case for long term flood accommodation also called for by the SFRA. This requirement needs to be added to option FR1.
Developers appear to regard a once in a hundred years flood event as being acceptable for meeting a planning application The extent of previous major flood events gives a measure of to the potential extent of flooding in river valleys. SFRA Section 6 contains an impressive list of historic flood events. Apparently, many local communities, including Colney and Cringleford parishes, were not approached for information about flooding in their areas. Such local information is likely to have been unrecorded. For example, in Colney a photograph shows major flooding in 1947 though this particular event is not listed in Section 6.
In section 6 of the SFRA the 1912 flood report indicates a return period of 800 to 1000 years: 56 years later the 1968 flood is given as 1000 year event. Return periods for current and especially future flood events require to be recalculated. Between 1878 and 2018 there were at least five major flood events, in 1878, 1912, 1947,1968 and 1993. This gives a periodicity of about 30 years for a major flood event. Section 6 of the SFRA lists dozens of significant floods events in the region of the GNLP. This raises serious concerns about suitability of new developments proposed in river valleys.

Full text:

Strategic Flood Risk
The Strategic Flood Risk Assessment (SFRA), published in November 2017, provides a detailed methodology for examining various flood factors which planning authorities and developers must take into account when planning applications are proposed (pp. 95-7).

The GNLP seeks to create a mass of new developments; many of these will be in the catchment areas of major rivers, including the Yare and Wensum. Such developments will affect natural drainage to rivers. In the Plan there is no specific commitment to natural processes of flood management which are highlighted in the SFRA.We support the case for long term flood accommodation also called for by the SFRA. This requirement needs to be added to option FR1.
Developers appear to regard a once in a hundred years flood event as being acceptable for meeting a planning application The extent of previous major flood events gives a measure of to the potential extent of flooding in river valleys. SFRA Section 6 contains an impressive list of historic flood events. Apparently, many local communities, including Colney and Cringleford parishes, were not approached for information about flooding in their areas. Such local information is likely to have been unrecorded. For example, in Colney a photograph shows major flooding in 1947 though this particular event is not listed in Section 6.
In section 6 of the SFRA the 1912 flood report indicates a return period of 800 to 1000 years: 56 years later the 1968 flood is given as 1000 year event. Return periods for current and especially future flood events require to be recalculated. Between 1878 and 2018 there were at least five major flood events, in 1878, 1912, 1947,1968 and 1993. This gives a periodicity of about 30 years for a major flood event. Section 6 of the SFRA lists dozens of significant floods events in the region of the GNLP. This raises serious concerns about suitability of new developments proposed in river valleys.