Transport | Development | Infrastructure
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C 16859 150729 LC ARW L
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29th July 2015
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Dear
CARDIFF LOCAL DEVELOPMENT PLAN 2006-2026
HEARING SESSION 9: H1.4 LANSDOWNE HOSPITAL ACTION POINT 7
NRW have now provided their further comments in response to the letter from Waterman on 8th July
2015 (ref. C 16859 150708 LC L). The Waterman letter was intended to provide clarification on the
main issues raised in the NRW letter of reply to Stuart Williams (Cardiff City Council) dated 18th June
2015.
NRW are maintaining their objection due to the fact that they ‘consider that the development itself
remains non-compliant with the requirements of Table A1.14 and A1.15 in TAN 15 for the proposed
access’, however it should be noted that TAN 15 confirms that:
1) Table A1.14 ‘should not be regarded as prescriptive, (and) provides indicative guidance as
to what the frequency threshold could be for different types of development described in terms
of annual probability of occurrence’.
Furthermore,
2) Table A1.15 ‘should not be regarded as prescriptive (and) provides indicative guidance on
what is considered tolerable conditions for different types of developments’.
TAN 15 recommends that each Site should be considered individually and a judgement taken in the
context of the particular circumstances which could prevail at that Site.
In this particular instance, it is solely the development access which falls outside the guidance
outlined in TAN15. The development plateau and building units themselves comply with the
guidance of both Table A1.14 and A1.15 in TAN 15.
Whilst consideration has been given to the proposed layout and the access road, it should be noted that
during the Q1000 event, peak flood velocities and depths off-site along Sanatorium Road and
Lansdowne Road will not satisfy the recommended criteria in TAN 15. It was therefore concluded that
raising the access road within the Lansdowne Hospital Site to comply with the recommended TAN 15
criteria will provide little benefit as the access off-site cannot be made compliant. It was considered
more important to retain the conveyance route for floodwaters through the Site to mitigate potential third
party impacts.
Notably, the Site and all access routes remain flood-free when climate change is not applied to the peak
flood flows.
During the 1.0%+CC APE scenario, flood waters initially spill over the left bank of the River Ely and take
approx. 4 hours to affect the top end of Lansdowne Road. It takes a further 5 hours for floodwaters to
reach the Site boundary. There are approx. 9 hours between the initial spill and the point when the Site
and access are affected by floodwaters. During the 0.1% APE, it takes approx. 7 hours between the
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time of the initial spill over the left bank of the River Ely to when floodwaters affect the access and Site
boundary.
There is a robust flood warning system available for the River Ely through Cardiff. This warning system
is important for the large numbers of residential properties around Victoria Park, Broad Street and
Fitzalan School, which are predicted to be affected by floodwaters during the 1.0%+CC APE. It is clear
therefore that with the presence of this existing warning system, would provide ample time for
preparations to be made for future residents. Notwithstanding this we would re-iterate that the proposed
building units would remain ‘safe’ in terms of all TAN15 guidance (with the exception of access) during
all extreme flood scenarios.
Emergency Planning falls under the responsibility of the Local Authority, in this case Cardiff City Council.
It is therefore a matter for Cardiff CC to determine whether they are satisfied that the risk is manageable.
It is envisaged that any planning consent would be subject to the provision of an Emergency Flood Plan
for all residents to ensure that residents take the appropriate action in the unlikely event of an extreme
flood, and remain safe without risk to life.
In addition to a robust warning service and a detailed Emergency Flood Plan, it should be noted that
formal defences along the River Ely currently serve to protect land and property in the immediate vicinity.
It is only when a 20% increase to flows is applied to the model inflows to account for climate change
that floodwaters encroach as far as the Site and associated access routes. It is possible that the River
Ely defences will be upgraded in the future to help reduce the flood extent in this residential area in line
with potential climate change. This would serve to defend the Site’s access from flooding during the
1.0%+CC APE and would therefore serve to improve accessibility to the site during extreme flood
events.
It is also noted that the site is currently occupied for healthcare use and as such there is an
existing level of risk. Given the nature of the existing use and the current flood risk to the existing
buildings (which are at a lower level than the proposed and are currently incompliant with
TAN15), the proposed re-development would effectively reduce the risks/consequences
associated with flooding.
It is noted that the other points raised by NRW have been considered, and are not judged as major
restraints to development. In summary;
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NRW request that the ‘Flood Compensatory Area’ be annotated on any future plans for clarity,
and accept that this can remain undeveloped over the development lifetime;
NRW note that the compensatory storage area is provided for the area of floodplain lost;
NRW consider that the approach to modelling bridges within the model can be resolved;
NRW have no further comments relating to the representations of bridge openings within the
model;
NRW confirm that the differences in the modelling carried out by NRW and Waterman are
relatively small, and confirm that the changes in approach do not fundamentally change the
outcome of the study;
It is clear that the only issue with the outline proposals is in respect of flooding to the off-site
highways/access. As the authority responsible for Emergency Planning, Cardiff CC should provide
comment on the access/egress arrangements. Planning Policy clearly stipulates that each proposed
development should be considered on an individual basis, within the context of local conditions. It is
concluded that there is adequate warning for residents to take appropriate action in the unlikely event
of an extreme flood event, and this may involve invacuation (remaining within the development site)
through the peak of the flood event, when the access/egress was not safe. A robust Emergency Plan
will ensure that this is managed and together with the increased level of the proposed buildings the risks
associated with flooding occurring at this site (currently occupied by a hospital) would be reduced. In
this respect, there are no reasons why the Lansdowne Hospital Site should not be allocated for
residential development, in what is already a large residential area.
Please do not hesitate to contact me if you require any further information.
Yours sincerely,
Andrew Wilkinson
Regional Director
Waterman Infrastructure & Environment Ltd.