Flood Risk Assessment
Proposed Change of use of the Vital recruitment
Office building 10 Grove Street, West, Boston,
Lincolnshire PE21 6TL from a B1 to D1 use, a
Children’s Day Nursery
M Norris
17
Contents Page

Introduction
Page 3

Site location and surroundings
Page 3

The proposal
Page 4

Flood sources and existing defences
Page 4

Flood Risk Definition
Page 5

Flood risk vulnerability classification
Page 6

Sources of flood risk in the Borough of Boston
Page 7

Recommendation
Page 7

Conclusion
Page 7 & 8

Flood Warning and evacuation plan
Page 9

Stages of Flood Risk
Page 10

Flood Map of Boston
Page 11
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
Page 2
Introduction
This site specific Flood Risk Assessment (FRA) has been written, taking guidance from the
National Planning Policy Framework 2012 and the Environment Agency.
Its purpose is to support the planning application submitted to Boston Borough Council for
the proposed change of use of the former Vital Recruitment Offices, 10 Grove Street, West,
Boston, Lincolnshire PE21 6TL to a Children’s Day Nursery.
The risk assessment will consider the category of risk, potential sources of flooding and any
existing flood defences in place.
Site Location and Surroundings
The proposed site is local to many schools, public parks, health services and educational
establishments. With the site being in the town centre it is close to all major road networks
along with bus, train links and cycle routes.
The property is located to the north of the town centre, adjoining the A16 trunk road and
the A52 trunk road access being from the cul de sac at Grove Street West.
Neighbouring properties are both residential and commercial in nature.
The site provides two entrances the first is an electronic keypad entrance for personnel, the
second is a separate gated vehicular access for approximately 10 vehicles.
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
Page 3
The site is located within the Black Sluice Internal Drainage Board and shown to be within
the flood risk area as per the Environment Agency’s flood plain maps.
The Proposal
This document is to be read in conjunction the planning application and other supporting
documents submitted.
The change of use to a children’s day nursery is proposed to take up the lease on a property
that is currently empty. It is located in a growing area within the borough of Boston and
provides additional means of childcare that are accessible within the main town centre.
Boston being a developing town has shown a need for this type of development and will be
keeping with local amenities.
The local area already has a children’s day nursery in the near vicinity, the proposal at this
location although a flood risk zone with the appropriate precautions and guidance set out
can be a viable option.
Flood Sources and Existing Defences
The flood plain map provided by the Environment agency show the site to be located in a
flood zone 3a (High probability) if there were no flood defences and Technical Guidance to
the National Planning Policy Framework (NPPF). The National Planning Policy Framework
Technical Guidance defines three levels of flood risk depending upon the annual probability
of fluvial occurring.
Zone 1 – Low Probability (<0.1%)
Zone 2 – Medium Probability (0.1% - 1.0%)
Zone 3 – High Probability (>1.0%)
The location compromises of land assessed as having between a 1 in 100 and 1 in 1,000
annual probability of river flooding (1% - 0.1%), or between a 1 in 200 and 1 in 1,000 annual
probability of sea flooding (0.5% - 0.1%) in any year.
If flood defences are taken into account this could significantly reduce the risk of flooding
from rivers or the sea, it could potentially take it into a low risk category.
Low risk is an area where flooding is unlikely except in extreme conditions. This means
within a low risk zone land is assessed as having a less than 1 in 1,000 annual probability of
river or sea flooding (<0.1%).
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
Page 4
Low means that each year, this area has a chance of flooding of between 0.1% (1in1000)
and a 1% (1in100). This takes into account the effect of any flood defences that may be in
this area.
Flood defences reduce but do not completely remove the likelihood of flooding and can be
over topped or fail in extreme weather conditions.
The proposed site is potentially at risk, to a greater or lesser degree, from failure of any of
the existing flood alleviation measures in the area.
Zone 3a – high probability
Definition
This zone comprises land assessed as having a 1 in 100 or greater annual
probability of river flooding (>1%), or a 1 in 200 or greater annual probability of
flooding from the sea (>0.5%) in any year.
Appropriate uses
The water-compatible and less vulnerable uses of land (table2) are appropriate
in this zone. The highly vulnerable uses should not be permitted in this zone.
The more vulnerable uses and essential infrastructure should only be permitted
in this zone if the Exception Test is passed. Essential infrastructure permitted in
this zone should be designed and constructed to remain operational and safe
for users in times of flood.
Flood risk assessments requirements
All developers proposals in this zone should be accompanied by a flood risk
assessment.
Policy Aims
In this zone, developers and local authorities should seek opportunities to:
 reduce the overall level of flood risk in the area through the layout and
form of the development and the appropriate application of sustainable
drainage systems;
 relocate existing development to land in zones with a lower probability
of flooding; and
 create space for flooding to occur by restoring functional floodplain and
flood flow pathways and by identifying, allocating and safeguarding
open space for flood storage.
Furthermore, the Borough Council’s 2010 Strategic Flood Risk Assessment (SFRA) shows
relative probability of flooding to be “medium probability”.
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
Page 5
Between Maud Foster Drain and River Witham / Boston Haven
13.21 This area is almost all at medium probability of tidal flooding south of Wide
Bargate, with a mixture medium probability of tidal flooding and high probability of fluvial
flooding north of Wide Bargate, although there is a large area of land with a low probability
of flooding along Tattershall road.
Flood Risk Vulnerability Classification
It is essential to consider the flood risk vulnerability based on the fact this is a proposal for
change of use.
The change of use to a children’s day nursery will mean the vulnerability category will
remain as more vulnerable as outlined in the table below. The previous occupancy of the
building was a labour recruitment office which would have fallen under the same category
and the property opposite to the proposal are residential flats, which would also be in this
category.
Table 2: Vulnerable uses of land
More vulnerable
 Residential institutions such as residential care homes, children’s homes, social
services homes, prisons and hostels.
 Buildings used for dwelling houses, student halls of residence, drinking
establishments, nightclubs and hotels.
 Non-residential uses for health services, nurseries and educational
establishments.
Table 3: Flood Risk Vulnerability and Flood Zone ‘Compatibility’
Flood risk
vulnerability
classification
(see table 2)
Essential
Water
Infrastructure compatible
Flood zone (see table 1)
Zone1
Key:
√
√
Zone 2
√
Zone 3a
Zone 3b
functional
floodplain
Highly
vulnerable
√
√
Exception
Test
required
Exception
Test
required
√
x
Exception
Test
required
√
x
√ Development is appropriate.
More
vulnerable
Less
vulnerable
√
√
√
√
Exception
Test
required
x
√
x
X Development should not be permitted.
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
Page 6
The table on previous page indicates that the proposed change of use is within a flood zone
where vulnerability would not compromise the change of use and development is
appropriate.
Sources of Flooding in Boston Borough
The Borough of Boston is situated in the Lincolnshire fens, at the downstream end of the
River Witham. The Borough straddles the low silt ridge that runs parallel with the western
shores of the Wash, separating the Wash from the extensive peat fens on the inland side of
the ridge. Boston itself and most of the older village settlements in the Borough are situated
along this ridge.
The following are potential sources of flooding affecting the proposed change of use
location:


The Haven (Tidal)
Maud Foster Drain
Tidal Flooding
Tidal flooding occurs when an exceptionally high tide, almost always accompanied by a
storm tide surge, overtops and/or breaches the tidal defences along a coastline or tidal
estuary.
Fluvial Flooding
Fluvial flooding can occur as a result of the overflowing or breaching of river or stream
banks when the flow in the watercourse exceeds the capacity of the river channel to
accommodate that flow.
Recommendations
Given the potential for flooding on the site and the classification of use under the NPPF it
would be prudent to adopt a precautionary approach with regard to the proposed
development to safeguard human life. Such aspects can be addressed by implementing an
evacuation plan detailed at the end of the document.
Conclusion
The Environment Agency’s Hazard Flooding Maps and data maps show the proposed
development site to be within an area of flood zone 3a. However the first 3km through
Boston channel has recently been changed to permanent reinforced concrete walls/ sheet
piling sea defences which are part of a rolling programme of improvements by the
Environment Agency. These defences are now certainly able to assist in the prevention of
future tidal flooding.
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
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The site is classified as a high risk area, however when taking into consideration flood
defences there is actually a relatively low risk of flooding from tidal breach and fluvial
sources. The tidal surge which happened in December 2013 did cause some flooding to
Boston however Grove Street, West was not affected.
The classification of vulnerability is “more vulnerable” however as indicated by the NPPF
development in this area is appropriate. As local properties/business fall into the same
category, the proposed outlined in the planning application should place no greater risk. It
is however important that a full flood evaluation is in place throughout the occupancy of the
tenancy.
It has been established that if a breach of the sea defences was to occur it would take a
considerable amount of time for the flood waters to reach the site by which time the
evacuation plan would have been employed and if necessary the site evacuated. The plan
will be held within the building so that all occupants are aware of the correct procedures to
follow.
I have no reason to doubt that the organisations will continue to monitor, maintain and
improve the existing drainage network in the prevention of flooding in response to the
predicted effects of climate change. Such organisations have a responsibility to inform the
public if these circumstances change.
Flooding from other sources is unlikely to affect the site
There will not be any person sleeping in the premises overnight, if the EA alert the business
to a potential flood risk, the staff will contact children’s parents as soon as possible or the
children will be re-located to high ground.
NPPF guidance 2014 states in paragraph 104 that change of use should not be subject to the
sequential and exception tests but will still need to meet the requirements of a site specific
flood risk assessment.
In final conclusion – with the flood defences currently in situ and the low risk of flooding
occurring, there is no risk to human life and therefore this proposal should be approved.
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
Page 8
Flood Warning & Evacuation Plan (FWEP)

If the proposed use is granted the tenants will ensure they sign up to the
Environment agency’s free Warnings Direct System. Flooding from tidal events is
predictable and if a flooding event is imminent the EA would advise the site occupier
accordingly.

Upon the designated telephone number receiving the warning that the site is at risk
of flooding, the assigned person will inform all occupants and customer/visitors of
the situation within the shortest time possible. This may involve a temporary closure
of the site. An example maybe a message service to inform customers that the site
will not open prior to their attendance where possible.

Visitors and occupants should familiarise themselves with the site and surroundings
and take note of the proposed evacuation plan.

The tenants will ensure their contact numbers are on site to be contacted in such
emergencies.

The flood evacuation plan fits in with other childcare policies like a critical incident
plan, where precautions are put in place for such events as flooding or possible
terrorist acts, the plan will indicate safe evacuation guidance and a safe point for all
occupants of the building to meet.

Security lighting will be put in place to ensure safe evacuation from the location.

Appropriate equipment such as clothing for these conditions will be available on site.

Local flood defence aids will be used where appropriate – for example sand bags.

The tenants will maintain overall responsibility for enforcing this plan and keeping it
relevant to change in circumstances throughout the course of their occupancy if the
proposal is granted.
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
Page 9
Stages of Flood Risk
The Environment Agency will issue 4 warning stages of flood risk as indicated below:
Symbol
Status
Severe Flood Warning
Severe flooding. Danger to life
Flood Warning
Flooding is expected. Immediate action required
Flood Alert
Flooding is possible. Be prepared
Warning no longer in force
Flood warning and flood alerts that have been removed in the last 24 hours

‘Severe Flood Warning’ – The site should not be occupied as there is likely to be a
threat to life. If for any reason, the site is occupied during a severe flood warning it
will be evacuated to safe ground as recommended by the appropriate authority who
will direct the evacuation towards Council operated centres outside the floodplain.
When evacuation has taken place regular contact will be made with the Environment
Agency flood control centre to ensure that all current information is available to
those affected. (EA Flood line – 0345 988 1188 or 0845 988 1188)

‘Flood Warning’ – Flooding is expected. Immediate action is required. People, pets
and valuables will be moved to a safe place or refuge away from the site. Gas,
electricity and water supplies will be turned off and flood protection equipment
(demountable barriers, sandbags etc) put in place.

‘Flood Alert’ - Flooding is possible, be prepared. The owner should be prepared to
act on their flood plan by preparing a flood kit of essential items.
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
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
‘Warning No Longer In Force’ – No further flooding is expected in the area. Upon
receipt of the all clear messages from the Environment Agency or then Police, the
local area may re-open and a visual inspection of the site conditions carried out to
determine whether it is safe to return to the site.
General advice given by the EA is that property owners should still be careful as flood water
may still be around for several days. If flooding has occurred on site the appropriate
measures should be taken to make the site safe for visitors to return.
Flood Map of Boston
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
Page 11
10 Grove Street, West, Boston, Lincolnshire PE21 6TL
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