proposed solar park development at cave farm, nr pitney, somerset ...

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J-3999.7-FM Flood Risk Assessment & SUDS Design, Cave Farm, Nr Pitney, Somerset V2
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3.0 EXISTING HYDROLOGY
The development site is located high within the catchment of a tributary that serves the River
Parrett. According to FEH CD-ROM 3 the catchment area upstream of the site is less than
1km 2 . The tributary then joins the River Parrett close to the town of Langport, around 4.2km
southwest of the site. The River Parrett discharges into the Bristol Channel at Burnham On-
Sea around 25km north of the site.
The greenfield surface water runoff rate for the site has been assessed using the ICP SUDS
method and WinDes Microdrainage software. The rates for several return periods are
included in Appendix C. A 1 year return period event produces a runoff rate of 39.4 l/s. A 1
in 100 year event is expected to produce a runoff rate of around of 122.3 l/s, including the
effects of climate change (+20% to SAAR values) this rises to 48.8 l/s and 151.3 l/s
respectively. Assessment of the design rainfall for the site; for a 1 in 100 year event, applying
a 6 hour storm duration, gives a design rainfall depth of 66.7mm.
Analysis of the Environment Agency flood map shows the subject site is entirely located within
Flood Zone 1. The relevant extract from the Environment Agency indicative flood map is
shown in Figure 3.1 below.
Approximate Site Location
No areas indicated to
be flood zone 2 or 3
Figure 3.1
Environment Agency Indicative Flood Zone Map
and FEH Catchment Area
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