Flood Risk Assessment For Application at: Gibstick Hall Farm Island

2 Nightingale Way, Catterall, Garstang, Preston, PR3 1TQ
Tel 01995 600733 email [email protected]
Flood Risk Assessment
For Application at:
Gibstick Hall Farm
Island Lane
Winmarleigh
Preston
PR3 0LB
email [email protected]
Contents
1. Introduction
2. The Site
3. Flood Risk
4. Existing drainage
5. Proposed Development
6. Mitigation Measures
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Introduction
ML Planning Services Ltd have been instructed by client Mr Hull to prepare a
Flood Risk Assessment for the application site at Gibstick Hall Farm,
Winmarleigh, in support of a planning application for the erection of a ring type
slurry store.
The Site
The application site is located approximately 4.2km to the south of Pilling Sands
and some 9.8km east of the River Wyre.
Application Site
Approximately 25 years ago a new sea wall was constructed at Pilling, which is
the first line of defence from tidal flooding, the old sea wall forming a second line
of defence should the former be breached. Local research supports the views of
the former owner of the site who has stated that the first line of defence appears
not to have been breached since construction. The applicant has lived on site for
years and has experienced no flooding issues.
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Flood Risk
From the Environment Agency’s Flood Map shown below it can be seen that the
application site is within Flood Zone 3. Flood Zone 3 is a high risk area with an
annual probability of flooding of 1% or greater from rivers and 0.5% or greater
from the sea. (If no defenses are in place).
However, the map also shows that the application site is in an area currently
covered by flood defenses. This is indicated by the area hatched in blue on the
map.
The Environment Agency has a Section 105 Model for the River Wyre. The
aforementioned flood defenses around the application site have been
constructed to reflect the results in the Section 105 Model and protect the land
accordingly.
Application Site
Existing Drainage
Water will drain into the existing network on site. There is no where within the site
that water could collect due to the natural topography. There will be a minimal
increase in surface water as a result of this planning application.
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Proposed Development
The proposed development includes the erection of a ring type slurry store.
Mitigating Measures
Although the site lives within flood risk zone 3, the flood defense measures
provide protection against the risk of flooding on the site. It is unlikely that any
fast flowing water will affect the application site in the event of a flood, due to its
location within the flood defense area.
Due to the nature of the flood risk, good warning is likely to be available prior to
any serious flooding and evacuation of people will be possible via the network of
adjacent roads. Registration with the Environment Agency’s Early Flood Warning
system is possible in this area and subscription to that service would be
recommended to the applicant.
In the unlikely event of a flood, the site can be easily evacuated via Island Lane
until the waters recede.
Tidal Flood Level
The highest recorded flood level for the site, as specified by the environment
agency, is 2.58m above a site datum of 1.71AOD. Therefore the proposed level
of the development should ideally be above this level.
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This means the highest recorded flood reached a height of 4.29AOD.
Climate Change
It is important when determining potential flood risks to a development to take
into account potential climate change activity which may add to the risk over the
lifespan of the development.
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Results
The highest recorded flood plus a contingency for climate change in the next 100
years results in a required floor level no lower than 5.22AOD.
The existing ground level of the site is 2180mm higher (7.3m AOD) currently, and
it can be therefore it can be proven that the site will not be at risk from flooding.
However, based on findings in the section 105 model detailed above, the 1 in
100 year modeled flood level for the area is 6.9AOD. This means the
development will not be at risk from flooding. The finished internal level of the
ring type slurry store shall be set no lower than the existing ground levels on site.
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