Examination of Witnesses (Questions 602
- 619)
WEDNESDAY 9 JANUARY 2008
MR DAN
HAWTHORN, MR
KEVIN REID
AND MR
RYND SMITH
Q602 Chairman:
Good afternoon, everybody. Our inquiry into flooding has once
again been the subject of parliamentary television. I welcome
from the Greater London Authority Mr Dan Hawthorn, their Senior
Policy Adviser for Planning and Development in the Mayor's Office,
and Mr Kevin Reid, who is one of their senior planners; and from
the Royal Town Planning Institute, Mr Rynd Smith, who is their
Director of Policy and Communications. You are very welcome and
thank you for your written evidence which you sent in advance.
That is much appreciated. London is a very important part of the
United Kingdom. Before I go into some specific questions about
your submission, you say that nearly 15% of London is at fluvial
or tidal risk of flooding. It may be that we should reflect on
all the other risks: the Thames, the Thames Barrier, the capacity
of the Victorian sewage system. All of these things have been
around as issues. Perhaps you could give us a short overview as
to what exactly are the flood risks for London and try to grade
your remarks against a measure of probability that these will
occur.
Mr Reid: You have touched on work
that we have been undertaking of the last year or 18 months. I
think we mention particularly in our evidence work that we have
done through the regional Flood Risk Appraisal, and that is where
these various different types of flood risk come from. May I cover
first tidal flooding, and we have identified five different sources.
One is from the River Thames, which is tidal through most of London,
and indeed that has gained a very high level of flood protection
through works that have been done since the 1953 floods. They
give in excess of once in 1000 year protection through the Thames
Barrier, the river walls and embankments, et cetera. You have
probably heard some of that detail from the experts that run all
of that at the Environment Agency. I am not an expert on it but
I may be able to answer some more detailed questions. That is
the tidal flood risk. The fluvial flood risk is a more mixed picture.
London has a great number of tributary rivers, some fairly large
and some fairly small. Most of them have some element of flood
defences along them. We have provided a small map in our evidence.
It may be hard for you to see the detail on that. We have that
information from the Environment Agency which collates all that
information for us. There may be a couple of things that they
may wish to update on that map. We can certainly supply a more
detailed version or, if you have it in electronic form, you can
zoom in and view it more closely.
Q603 Chairman:
If you could send us the web link, we could all look at that.
Mr Reid: Suffice to say that the
level of flood protection along those tributaries varies in some
cases from the order of about once in 20 years up to and in excess
of once in 100 years. It is a different picture for different
tributaries. I would point out that much of the land along those
tributaries is still in some form of open space use. It is not
necessarily the case, although it does occur, that building has
happened right up to some of the banks and indeed over the top
of some of those rivers. I am sure you can envisage the sort of
situation. If I may continue with these five sources, the third
source is from groundwater. During our Regional Flood Risk Appraisal,
we found little actual evidence of any history of groundwater
flooding within London, although the Environment Agency has recently
told me that there have been some cases. I am keen to investigate
with them just where and when that has occurred because it had
not initially been flagged up to us. The fourth source, and you
mentioned it, is sewer flooding. That does occur in two aspects:
firstly, the overflow of the Victorian sewer infrastructure, which
takes both rainwater and foul sewage water. You are probably aware
that the Government announced in March of last year a very large-scale
tideway sewer project of the order of about £2 billion in
order to accommodate the vast majority of those overflows. That
project is still being finalised. The go-ahead in general has
been given. It will take up until about 2020 to put in place.
It tends not to affect any properties as such. Indeed, the reason
that that combined sewer system overflows into the River Thames
really is in order to prevent the flooding of rainwater and mixed
sewage onto streets and properties. That is what the Victorians
built as their safety-valve. The fifth source of flooding, which
I have deliberately saved until last, is from surface water; that
is, direct from rainfall. This was one of the key matters that
our Regional Flood Risk Appraisal brought out, that it does happen
in London reasonably frequently, as far as we can make out. In
the summer of last year there was surface water flooding in some
parts of London. I am told that affected parts of 15 boroughs.
What we were most concerned about was that there was not really
any central co-ordination or overview about where and why that
flooding had taken place, or indeed any consistent record of when
it had happened so that any particular organisation could go and
look at this as a problem to be addressed. Perhaps in its nature
it is somewhat haphazard in where it will happen. It could be
down to a localised thunderstorm or a localised blockage of the
drainage system. There were no consistent records being kept.
Q604 Chairman:
Did the old GLC ever have any overarching responsibility for flooding?
Mr Reid: You are testing my knowledge
a little. As far as I know, there was a drainage division of the
old GLC. Quite what data records they held, I could not answer.
We do not have anything much from the former GLC at the GLA today.
Q605 David Taylor:
On your map we seem to have this spuriously accurate figure again
of one in 1000 year return period for flooding. How on earth can
we calculate figures at that sort of scale? We are going back
to before the time of William the Conqueror. That is an artificially
reassuring figure, is it not?
Mr Reid: I am told that the level
of protection is somewhat in excess of that once in 1000 years.
Q606 David Taylor:
How on earth can we be that precise?
Mr Reid: It is not a GLA figure.
This is information that essentially I am reporting to you. I
am sure it has been reported to you by the Environment Agency.
Q607 David Taylor:
Have you ever challenged that? Have you ever asked the origin
of that degree of certainty?
Mr Reid: We have not. We have
accepted that the Environment Agency has a level of expertise
on this. They have been looking after these flood defences for
however many years. They discuss these things with colleagues
in Holland. I am sure that I remember hearing a figure that the
Dutch think they have about one in 10,000 year protection.
David Taylor: I just do not accept the
figures. They are absolutely meaningless. You are quoting in good
faith what the Environment Agency tells you.
Q608 Chairman:
This does raise an issue. You have described the five areas where
there are potential flood risks for the capital. One of the issues
which the Committee has been exploring is the intensity with which
these events occur. There are definitions on a probability basis
of an extreme weather event. I would not like to be around when
the one in 1000 year event occurs. What we have seen are concentrations
over very short spaces of time of these events, which puts a new
time dimension. Therefore, the question of surface run-off and
sewer capacity seem to me to take on a different viewpoint than
a one in X year event, which may be spread out over a long time
period, as opposed to one of these events that might occur within
a short time period. Have you done any sensitivity testing on
that for London's flood risks?
Mr Hawthorn: In a way, that is
precisely what our flood risk assessment identified, that the
clear and present danger is not from the fluvial flooding but
particularly from surface water flooding, which in research terms
is very poorly understood as to how the risks accumulate and arise
and whether and how it might be possible to predict events with
any certainty before they happen, in the way that sometimes happens
with fluvial flooding. Our Drain London project is for the first
time trying to co-ordinate the local authorities, Environment
Agency, water companies and so on to pool their expertise, understanding
and resources and to try to get a grip on this. That is what we
are just embarking upon.
Q609 Chairman:
Have you done any modelling whereby, for example, you have said
that you would just look at London as an entity and run a computer
model that shows that in an hour we have one, two, three, four
inches of rain and in two hours, five, six, seven inches of rain
to see what actually happens?
Mr Reid: No, we have not done
that. I would stress that the GLA's role is obviously a strategic
role, as set up under the Act. We are deliberately a fairly tightly
constrained organisation. We take information from the other government
experts, the Environment Agency and the water companies in some
cases. We ask them some questions but we do not have the resources
to build and develop our own models in that sense.
Q610 Chairman:
Do you think that somebody should do that in the light of the
intensity? Part of the reason this inquiry is taking place is
that in those areas that flooded, like Tewkesbury for example
and indeed Hull and Sheffield, they experienced such intensity
in two days, effectively a month's rainfall.
Mr Hawthorn: I think it is right
to say that the risks can be assessed not only by an assessment
of how many inches of rainfall but also how the infrastructure
is equipped to deal with it. If the infrastructure is equipped
to deal with it well, then you can deal with more than you can
if the drains are blocked or poorly maintained.
Q611 Chairman:
Do you think that somebody should do that work for London, given
the sensitivity of what is in the capital?
Mr Hawthorn: That is precisely
what Drain London has been set up to explore doing. The intention
is, first, to understand the infrastructure and then the hydrological
monitoring on top of that. It is putting those two pieces of the
picture together that gives you a proper assessment of the risk.
Q612 Miss McIntosh:
When we had local flooding in the Vale of York, way back in 2000,
it was my distinct understanding that each district council does
a form of mapping. One of the confusing things is that you have
the Met Office doing one sort of mapping together with the Environment
Agency and the insurance companies doing another sort of mapping
and forecasting. It is my understanding that all local authorities
do this. Are you saying to us that you are unique and that you
do not do this kind of mapping down to house postcodes and the
impact? For example, your role in floods presumably is to issue
sandbags?
Mr Reid: No, that is very much
a local authority role. It is worth being clear that some local
authorities do that and others have taken a clear decision that
that will not be part of their role.
Q613 Miss McIntosh:
In the event, and I know it is not so much the role of this Committee,
that for example sandbags are available to some and not other
local authorities, will it not seem clear that you should perhaps
take on a co-ordinating role here?
Mr Reid: To be clear, the GLA
itself would not do that but we are working with a group that
the Government Office for London has set up, which is trying to
co-ordinate exactly those sorts of issues across London. There
are adjoining boroughs which have a different approach. I cannot
really say whether a similar case arises outside London. I honestly
do not know. As far as I am aware, the initial point that you
made about each local authority mapping these has only recently
started to occur with the requirement under PPS25 for them to
produce a strategic flood risk assessment. I was not aware—and
I am happy to be corrected—that all local authorities were
doing that previously.
Q614 Chairman:
Let us ask you a couple of quick questions arising out of the
Pitt Review. One of the conclusions there was that the right to
connect to a public sewer whenever new development took place
should effectively be abolished. Is that something that you think
is a relevant issue for London?
Mr Reid: It is certainly an issue
for London. Perhaps I ought to say that it is not something that
we had particularly investigated or researched before seeing the
Pitt Review. This is something of a view at short notice. It seems
to us, and given that we have identified particularly surface
water as a high risk for London, that at the very least that right
ought to come with a certain amount of responsibility really to
demonstrate that before connecting reasonable steps have been
taken to reduce, possibly eliminate, some or all of that surface
water drainage, for example through sustainable drainage techniques,
perhaps even water butts or diverting the roof gullies to a garden
or a pond or a permeable surface, that sort of thing.
Q615 Chairman:
So you would agree with Pitt's suggestion that the right to have
an impermeable surface at the time you develop something should
be removed?
Mr Reid: Yes.
Mr Hawthorn: It should also be
conditional.
Mr Reid: That is particularly
given the intensity of built development in London. There are
some locations where there is very little choice other than to
connect into a surface water sewer. There are other more suburban
locations where it would be fairly easy and relatively inexpensive
to have your new house or perhaps the extension to your property
draining sustainably, and it could indeed drain the existing premises
as well to give an overall reduction in surface water run-off.
Mr Smith: It is fair to say that
this is an issue that the Royal Town Planning Institute has been
thinking on for some time. We have been strongly urging, as a
matter of general principle through the Government's consideration
of the Householder Development Consents Review, about what you
can do that requires planning permission in relation to changes
to individual dwelling units. In fact, there is a need to look
very carefully at the proliferation of hard surfaces and the degree
to which they are a generator of catchment flood risk. Our key
thought process here has been to take the view that it would be
important not to over-burden the planning system with thousands
of additional applications for planning permission to put down
small areas of hard-standing. We believe that it ought to be possible
to have conditional classes of permitted development where a particular
set of techniques is identified that will return the piece of
land that you wish to pave effectively to its unpaved state, enabling
water to pass through it and soak away and effectively to re-enter
the groundwater rather than running off and entering catchments
and exacerbating flooding. Interestingly, work was done on this
going back to about 1998 in Australia. The Commonwealth Scientific
and Industrial Research Organisation did a very interesting piece
of work there that looked at the practical identification of techniques
that could be used. In the City of Melbourne in Australia a group
of local authorities, the Association of Bayside Municipalities,
asked what this means for planning and how we can promote, through
the way we exercise planning control, the take-up of those techniques
to start winding some urban land back in a sense almost to rural
permeability without entailing excessive cost. That is a set of
work streams that would obviously have to be re-done in the geological
and climatic conditions prevailing.
Q616 Chairman:
Is that the kind of thing that ought to be put into building regulations?
Mr Smith: Yes, absolutely, but
we would strongly be urging that where those sorts of techniques
can be diagnosed, rather than taking the approach of decanting
that sort of stuff into the planning system and creating a lot
of new, minor applications, in fact performance requirements in
the building regulations could deliver significant improvements.
Certainly, part of the issue has to be the way that permitted
development for both householders, and indeed for other classes
of use or development, are constructed. At the moment, householders
have really quite substantial rights to pave over their garden
space. Particularly in the London context, but I would argue across
urban England, there is a very strong argument for taking a fresh
look at those rights.
Q617 Mr Drew:
It would be interesting to know in the case of London and the
degree to which the failure to adopt many sewers because of developers
not reaching the requirements of building standards if the Pitt
proposal could make that work. The danger with this is that it
is the law of unintended consequences. Obviously we want high
standard sewers but many builders clearly do not build to that
standard. Therefore, the sewers are not adopted and therefore
it is not the developer's problem in a sense. Clearly, until we
get the changes, it is not the local authority's problem; it is
the householder's problem. It really is one of neglect of the
problem. I do not know what your views on that are.
Mr Reid: I am not aware that it
is a particularly significant issue in London that sewers are
built below the standard where they are ready to be adopted. Being
the strategic authority, it is not an area that the GLA gets into.
If you have evidence to the contrary—
Q618 Mr Drew:
Certainly it happens in other parts of the country. It is interesting
that it may not be so in London.
Mr Reid: All I can say is that
it has not come to us as a matter that has been drawn to our attention.
If it was happening on a fairly common scale, I imagine that it
would have come to us at some point.
Q619 Miss McIntosh:
This is a point of clarification for Mr Smith. You mentioned a
specific subject about planning applications, which I think you
did say could be dealt with by building regulations.
Mr Smith: One of the things that
is necessary here is to look at the range of options that might
be available for best ensuring that we reduce the potential flood-generating
effect of putting down hard surfaces without planning permission.
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