26th
September 2002. Land management of unpaved areas can
modulate run-off but inevitably there will be times when the intensity
and volume of storm water exceeds the capacity of the underground
infrastructure to carry it away. Modelling issues are discussed,
especially when considering unconfined flows. 1-D modelling is well
developed but 3-D stretched current computing power. Getting flooded
with water is bad enough but sewage (even diluted) is far worse. Is
there an argument for keeping some of the storm water out of the
sanitary sewers? The Workshop recommends giving consideration to
engineering selected roads as flood-routes for extreme events, which
would require co-ordination between agencies.The report contains 29 pages, 5 references, illustrations and the contact details of the participants
24th
September 2003 Basically the answer was "no". However
that's not to say that things are bad at present but that in a changing
climate (meteorologically and otherwise) it is time to question and
move forward; we could and should do better. There can be tough
strategic and financial choices; engaging the public in choosing
between the options and getting their buy-in to the solutions can prove
valuable. Ultimately it is they who pay the bills.
The report contains 50 pages, 11 references, illustrations and the contact names of the participants.
30th April
2004 Much has been delivered already regarding sanitary
sewerage and reducing the risk of urban flooding. Properties classed as
being at risk of flooding have been reduced, but internal flooding has
remained constant at about 25/100,000 properties. Are the unaffected
willing to pay the massive bill for further reduction which a linear
extension of historic practice would entail? High resolution
precipitation-radar reveals spatial variation in rainfall is much
greater than rain-gauges suggested. Existing models for predicting
run-off are good but based on relatively few calibration data. More
long term data and flow-monitoring are needed to refine models. Almost
inevitably further reducing the risk of flooding in a time of inherently
increasing difficulty (because of climate change) will require a
step-change in approach.The report contains 43 pages, 11 references, illustrations and the contact details of the participants
6th July 2005
Combined Sewer Overflows (CSOs) are essential safety valves for the
sewerage network. When storm events are intense enough there
is bound to be more stormwater than sewers can carry. In its 2000-2005
Asset Management Plan the water industry built and upgraded 2,500-3,000
CSOs at a total cost of about £1 billion. In 2000 screening
CSOs was unproven technology and it has improved considerably by
research and experience. In the rush to complete schemes some of the
work was poor. In such intensive programmes application of
"partnering", with its sharing of information, would have considerable
benefits. There should be attention to the eventual operation and
maintenance of installations. Good construction/contracting practice
and adequate training are vital. There is much to learn from post
project appraisal.The report contains 56 pages, 6 references, illustrations and the contact details of the participants.
8th March 2006
The most popular runoff process in use is more than 30 years old. It
was based on field data but they have not been documented formally and
few understand them. Further field work is overdue, especially for
evaporation and depression storage on impervious surfaces. The data on
surfaces are too general. There is need for standardisation to extend
the life and transferability of models. The report describes ways in
which surface characterisation, data capture and processes could all be
improved.The report contains 56 pages, 6 references, illustrations and the contact details of the participants.
18th April
2007 The ability to model urban run-off is essential in
order to protect people and assets cost effectively and with
confidence. We need to improve understanding of the fundamentals and to
supplement the original field work that underpins the process models.
Digital mapping, computing power and remote sensing combine to make
surface characterisation better. Particular attention is needed for our
understanding of drainage from roofs and surface water entry via
gullies. Urban creep (paving, extensions etc)confounds run-off models;
a standardised means of accounting for it in the next generation of
models is essential. There is a need for communication between river,
sewer and STW models. The report contains 33 pages, 3 references, illustrations and the contact details of the participants.
19th April 2010 The objective of using green infrastructure (GI) for rainwater is to reduce the rate at which rainwater falling
on urban areas runs off and also the total amount of that runoff. It might be complemented by grey
infrastructure where GI does not have sufficient capacity to treat all of the runoff but in that case the grey
infrastructure can be much smaller, less expensive and less disruptive to build.The report contains 32 pages, 11 references, illustrations and the contact details of the participants.