WATER
Draft PUSH Sustainable Development SPD
Resource Document
Introduction
Water
Energy/CO2
Materials and Waste
Health and Wellbeing
Green Roofs
Sustainable Management
Infrastructure and Major Developments
April 2009
1
WATER
Resource Document Contents
Chapter
Chapter title
Introduction
1
1.1.
1.2
1.3.
1.4
1.5.
1.6.
1.7.
2
2.1
2.2
2.3
Introduction to this Guidance
Purpose of this Resource Document
Scope of this Resource Document
Government Policy
South East Plan Policies
PUSH Planning Policy Framework
The Council Core Strategy Policies
How to use this Resource Document
Sustainable Development: General
National Policy Drivers
Evidence Base in South Hampshire
Design and Access Statements
2.4
2.5
Code FSH and BREEAM
Sustainability Checklist
3
3.i
3.1
3.2
3.3
3.4
3.5
3.6
3.7
Introduction to Water
Water Appliances
Rainwater Harvesting
Grey Water Recycling
External Potable Water
Reduction in Surface Water Runoff
Flood Risk
Adaptation to Climate Change
THIS VOLUME
Water
Energy/CO2
THI
S VOLUME
Volume
4
4.i
4.1
4.2
4.3
4.4
4.5
4.6
4.7
Introduction to Energy/CO2
Natural Daylight
Passive Solar Heat Gain
Natural Ventilation
Drying Space
Energy Efficiency
External Lighting
Small Scale Zero/Low Carbon
Technologies
2
WATER
Materials and Waste
Health and Wellbeing
Green Roofs
Sustainable Management
Infrastructure and Major
Developments
4.8
Zero Carbon Residential Developments
5
5.i
5.1
5.2
5.3
5.4
Introduction to materials and waste
Construction Waste
Construction Materials
Waste Recycling
Composting
6
6.i
6.1
6.2
6.3
6.4
6.5
6.7
6.8
6.9
7
7.i
7.1
8
8.i
8.1
8.2
8.3
Introduction to Health and Wellbeing
Biodiversity
Noise
Private Space
Lifetime Homes
Pollution
Accessibility
Residential Density
Security
Introduction to Green Roofs
Green Roofs
Introduction to Sustainable Management
Building User Guides
Considerate Constructors Scheme
Construction Site Impacts
9
9.i
9.1
9.2
9.3
9.4
Introduction to Infrastructure and Major
Developments
Waste Management Infrastructure
Green Infrastructure
Large Scale Renewable Energy
Major developments
A
B
Model Essential Requirements
Sustainability Checklist
Appendices
3
WATER
3. Water
3.i. Introduction to Water
This chapter looks at two aspects of water
management:
1
the use of potable water (i.e. treated
water from the tap), with the aim to
reduce its use both in the home and
in non-residential buildings as well
as in associated outdoor spaces.
2
the way in which we manage rainfall
in new development, identifying
ways to reduce surface-water runoff in new development and reduce
flood risk.
Potable Water
Water is becoming increasingly scarce as demand continues to increase
dramatically. Over the last 30 years water consumption in the UK has
risen by 70%. The average domestic water consumption is
approximately 160 litres/person/day (150 l/p/day for new dwellings).
There are many actions that can be taken to minimise water
consumption and all should be considered. Sanitary use of water within
a dwelling is significant and a number of steps can be taken to minimise
consumption. Water-saving/efficient devices and appliances are just as
economical to install into an existing building as they are at the initial
construction phase.
Once all the possible water efficient appliances have been fitted,
further significant efficiencies can be attained through recycling of
rainwater and ‘greywater’. Sustainable Drainage Systems (SUDS) help
to minimise the unnecessary loss of water to the mains drainage
system and also reduce the likelihood of damaging and polluting flash
floods.
Measures for rainwater harvesting, greywater drainage and SuDS are
more economical to install during the construction phase than as part
of a retro-fitting scheme, particularly in domestic situations.
4
WATER
External
Tap 13%
Washing
machines 9%
Dishwashers 2%
Unknown 1%
Internal Tap
25%
Showers and
Baths 24%
WC Flushing 25%
Typical domestic water consumption (Source: Mid Kent Water)
5
WATER CONSUMPTION
3.1. Water Consumption
Buildings can be designed with appliances and fittings and
management systems can be put in place to make the predicted water
use of that building substantially lower than would otherwise be the
case. Although the subsequent water consumption behaviour of the
building’s users cannot be controlled the opportunities for using water
much more sparingly are in place.
In residential buildings the following efficiency measures can be
employed to reduce the building’s predicted water consumption
APPLIANCES
Spray Taps
Flow
Regulation
Waterefficient
Toilets
Urinals
Showers
Washing
Appliances
Meters
DETAILS
Many taps can be retro-fitted with a spray head to reduce
the flow of water. Account should be taken of who would be
using the tap and for what purposes.
Due to the water pressure being set by water companies,
regulation is generally more applicable than restriction. The
maintenance of a standard flow rate can be achieved by inpipe fittings, or outlet fittings, such as specially adapted
shower heads.
Toilets can account for 25% of water-use in a typical
household. Low-flush toilets and dual-flush toilets are
inexpensive ways to rein in the amount of water used. Lowflush toilets simply use less water in the cistern, whereas
dual-flush toilets can vary the flush depending on the
amount of waste.
Depending on the potential usage of urinals, systems to
restrict flushing, or even remove flushing, can be employed.
Generally, showers use less water than baths, however this
is mainly due to personal preference when washing. Power
showers are actually more likely to waste water than a bath.
Fitting a flow-regulation device to the shower head can
maintain both the comfort and water-saving aspects of
usage.
Although not strictly a construction issue, many new homes
are fitted with washing machines and dishwashers, the use
of energy efficient appliances (usually A or B rated) can help
to cut water usage.
Water meters do not specifically save water themselves but
can cut consumption. By linking water habits to a charging
structure, it is likely that householders and businesses alike
will take steps to ensure that less water is wasted.
Devices and Appliances to Save Water (Source: Maidstone Borough Council
Sustainable Construction SPD Part 1- Using Water July 2006)
6
WATER CONSUMPTION
Code Credits
There are mandatory requirements for decreasing levels of predicted
water consumption at different levels of the Code and there are a
maximum of 5 potential credits in Wat 1.
Water consumption
Credits
Mandatory Levels
(litres/person/day)
≤ 120
1
Levels 1 and 2
≤ 110
2
≤ 105
3
Levels 3 and 4
≤ 90
4
≤ 80
5
Levels 5 and 6
(From Wat 1 (Internal Potable water Use) CSH Technical Guide)
Credits are based on the predicted average household consumption
calculated using the BRE Code Water Calculator and includes any
reductions of mains supply due to rainwater harvesting and/or
greywater recycling systems.
BREEAM Credits
BREEAM credits for non-residential buildings are awarded in the
following ways:
 based on the improvement over standard specification of water
fittings, calculated using the BREEAM water calculator including the
reduction of supply through rainwater or grey water systems.
 where evidence that a water meter with a pulsed output will be
installed on the mains supply to each building.
 where evidence that a leak detection system is specified or
installed.
 where proximity detection shut off is provided to water supply for
all urinals and
 where evidence that there are established and operational
maintenance procedures covering all sanitary fittings.
 where evidence water consumption is monitored and recorded at
least once every quarter.
 Where evidence is provided to demonstrate the specification of
systems that collect, store, and where necessary, treat rainwater or
greywater for WC and urinal flushing purposes. (Some BREEAM
assessments only, e.g. BREEAM Schools)
7
WATER CONSUMPTION
Model Essential Requirement 3.1
The Council requires all residential development to achieve at least:



Level 3 of the Code
(mandatory 3 No. Wat 1 Code credits required, ≤ 105 l/p/day)
4 No. Wat 1 Code credits ,≤ 90 l/p/day, from 2012*
Level 6 of the Code
(mandatory 5 No. Wat 1 Code credits required, ≤ 80 l/p/day) from
2016*
The Council requires all non-residential and multi-residential
development above 500 sqm of floorspace to achieve at least:



*
50% of the available BREEAM Water credits until 2011*
60% of the available BREEAM Water credits from 2012*
70% of the available BREEAM Water credits from 2016*
At the time that planning permission is granted
Compliance Check
Residential:
Up to 2011: Level 3 certificates at both design and post construction
phases
2012-2016: Code FSH Assessor’s reports at design stage and post
construction stage stating at least 4 no. Wat 1 credits achieved.
From 2016: Level 6 Code FSH certificates at both design and post
construction phases
Non-residential and Multi-residential:
Up to 2011: BREEAM Assessor’s reports at design stage and post
construction stage stating at least 50% of BREEAM Water credits
achieved.
2012-2016: BREEAM Assessor’s reports at design stage and post
construction stage stating at least 60% of BREEAM Water credits
achieved.
From 2016: BREEAM Assessor’s reports at design stage and post
construction stage stating at least 70% of BREEAM Water credits
achieved.
8
WATER CONSUMPTION
Sustainability Checklist
Q.3.1: What measures will be taken to maximise water efficiency in
buildings?
Planning Implications
More efficient appliances are unlikely to have any implications for the
external visual appearance of buildings.
Further Guidance and References
ENVIRONMENT AGENCY, National Water Demand Management Centre, A Study of
Domestic Greywater Recycling (2000)
ENVIRONMENT AGENCY: Assessing The Cost Of Compliance With The Code For
Sustainable Homes WRc Ref: UC7231.
CIRIA, Buildings that Save Water (2001)
CIRIA. C522, Sustainable Urban Drainage Systems - design manual for England and
Wales, (2000)
BRE, Water Conservation: a guide for installation and maintenance of low-flush WCs
(1997) Available from CRC Tel: 020 7505 6622
BRE, Water Conservation: IP 2/00, Low Flow Showers and Flow Restrictors. (1997)
Available from CRC Tel: 020 7505 6622
DEFRA Water Supply (Water Fittings) Regulations, (1999)
9
RAINWATER HARVESTING & GREYWATER RECYCLING
3.2. Rainwater Harvesting and Greywater Recycling
Rainwater Recycling
Rainwater harvesting involves the channelling of water from one or
more roofs via a filter into a storage tank placed in a convenient
location. Table x displays the potential for water collection, depending
on the size of roof used. Consequently, the installation of a single
collection system is often more suited to a larger building; with smaller
buildings benefiting from a linked, communal system, such as on a
housing estate.
Rainwater harvesting potentially reduces the initial consumption of 150
litres/person/day to 80 l/p/d, although this will be dependent on
rainfall and roof area. The potential rainwater yield is illustrated in the
table below. The mean annual rainfall in South Hampshire is
approximately 800mm
Table x
Roof Area (m2)
Annual Rainwater Yield (litres)
50
24000
Average Annual Consumption
(litres)
75
36000
100
48000
125
60000
150
72000
55000
Rainwater Annual Yield (litres)( Source: The Environment Agency)
Water harvested from roofs has been shown to be suitable for use in
toilets and washing machines. Additionally, it can be used for other
non-potable purposes, such as general cleaning. A dual water supply
ensures that when rainfall has been minimal, appliances such as
washing machines (and any other use that relies principally on
rainwater) can be switched to the mains supply.
The installation of a harvesting system is more cost-effective and less
energy-intensive if incorporated at the outset of construction.
The size of the storage tank is determined by considering the amount
of water available for storage (a function of roof size and local average
rainfall), and the amount of water likely to be used (a function of a
building’s occupancy and function).
Where the installation of a rainwater system is unlikely (such as in an
existing single dwelling), smaller measures can be taken usefully e.g.
the use of garden water butts, which cost less and provide a quicker
10
RAINWATER HARVESTING & GREYWATER RECYCLING
return on investment. All harvesting systems will require periodic
maintenance to ensure their ongoing quality and effectiveness.
Rainwater collected from roof and filtered (1)
Calmed inlet (2) prevents disturbance of the float
switch and sediments.
Submersible pump (3) delivers water via a floating
suction filter (4) to WC, washing machine and garden
tap.
Combined pressure switch/flow controller (5) turns
pump on and off when required and provides dry
running protection.
Float switch (7) controls
solenoid valve (6) to provide
mains water top-up via
funnel (8).
Pressure hose (9) and cables
are ducted through to the
house through a 110mm
drainage pipe (10).
Overflow trap (11) prevents
foul odours from drains.
Typical domestic system
Commercial systems are usually larger, more sophisticated
versions of those used in the domestic situations.
Typical commercial system
Source: rainharvesting.co.uk
11
RAINWATER HARVESTING & GREYWATER RECYCLING
Benefits
The main advantages to installing rainwater harvesting systems are:





Up to 50% of main supply water can be substituted by stored
rainwater thereby reducing overall water supply costs
significantly;
Dependence on the mains water supply is reduced and in remote
areas rainwater harvesting can provide an off-site water supply;
Used as part of a storm-water management scheme it reduces
the amount of storm-water runoff and can control the flow-rate
off site;
The sustained water savings add value to the property as well as
demonstrating commitment to conserving natural resources;
Can dramatically reduce attenuation volumes for restricted run
off situations.
12
RAINWATER HARVESTING & GREYWATER RECYCLING
Greywater Recycling
Greywater – the water that has already been used in hand basins,
baths and showers – can be recycled to save up to 49 litres per person
per day(l/p/day) representing on average 33% of household water
use. After basic processing, the water can be reused around the home,
including flushing toilets, watering the garden or general cleaning
purposes i.e. windows, floors etc. The installation of a greywater
recycling system is more cost-effective and less energy-intensive if
incorporated at the outset of construction.
Greywater Recycling
13
RAINWATER HARVESTING & GREYWATER RECYCLING
Potential water savings with
greywater recycling
Source: Maidstone Borough Council Sustainable Construction SPD Part 1- Using Water
July 2006
14
RAINWATER HARVESTING & GREYWATER RECYCLING
Case Studies
The Lighthouse
The Kingspan “Lighthouse” at the Building
Research Establishment (BRE) site at
Garston is a prototype house, the first to
receive BRE Code for Sustainable Homes
Level 6 certification in June 2007.
Rainwater collects from the roof into a
gutter which drains via a chain into the
underground tank. The rainwater collected
is used to supply the washing machine.
The Lighthouse uses greywater to flush
the toilets.
Underground storage tank
Code Credits
The Code for Sustainable Homes has no specific credits for reducing
the consumption of potable water in the home by rainwater harvesting
or greywater recycling but it will help to gain extra credits under Wat
1. The amount of rainwater or greywater that it is predicted can be
collected and used per person is subtracted from the total potable
water used per person to arrive at the final predicted potable water
consumption per person in Wat 1.
Wat 2 encourages the recycling of rainwater/greywater for external
use (for landscape/garden watering). See section 3.3 below.
BREEAM Credits
There are specific extra credits under some BREEAM assessments for
greywater/rainwater recycling e.g. BREEAM School and BREEAM Courts
(Wat 5). Other BREEAM assessments, e.g. BREEAM Office, do not
15
RAINWATER HARVESTING & GREYWATER RECYCLING
have specific extra credits however all non-residential developments
which reduce their total water consumption via rainwater harvesting
will achieve more credits under the water consumption heading. (e.g.
Wat 1 for BREEAM Office).
Model Essential Requirement 3.2
The Council requires all residential development (of 10 dwellings and above)
and all non-residential and multi-residential development (over 500 sqm of
floorspace) at the detailed planning application stage to either:
Submit details of the rainwater harvesting and/or grey water recycling
systems supplying all WC flushing and other appropriate uses for that
development
Or:
Submit a feasibility study for rain water harvesting and/or grey water
recycling systems for that development and implement its recommendations.
Compliance Check
Code FSH or BREEAM Assessor’s report to confirm the amount of
predicted water consumption for each building or development which
is reduced separately by rainwater harvesting and grey water recycling
systems.
OR
(Where rainwater harvesting or grey water recycling systems absent)
Receipt of a feasibility report clearly showing how either or both
systems are not feasible in practical physical terms for any particular
building or development.
Sustainability Checklist
Q.3.2: What percentage of the development’s predicted water needs
will be served by rainwater harvesting and/or greywater recycling?
Planning Implications
The visual impact would normally be minimal (ground level inspection
covers) as the storage tanks are typically sited underground, or under
the building’s roof. There may be implications for tree planting which
would not be possible over or near to underground tanks.
16
RAINWATER HARVESTING & GREYWATER RECYCLING
Further Guidance and References
WATER REGULATIONS ADVISORY SCHEME. Information and Guidance Note 0902-04. Reclaimed Water Systems. Information about Installing, Modifying or
Maintaining Reclaimed Water Systems (1999)
ENVIRONMENT AGENCY, Conserving Water in Buildings 4: Rainwater re-use,
www.environmentagency.gov.uk
UK RAINWATER HARVESTING ASSOCIATION (UKRHA) http://www.ukrha.org
Figures for UK rainfall are available from the Met Office www.met-office.gov.uk
CIRIA Rainwater and Greywater Use in Building, Best Practice Guidance (2001).
WRAS Reclaimed water systems – information about installing, modifying or
maintaining reclaimed water systems”; 9-02-04, (1999)
BSI BS1710: Specification for identification of pipelines and services, (1984)
BSI BS EN 12056-3:2000: Gravity drainage systems inside buildings. Roof drainage,
layout and calculation, (2000).
Grey Water website: http://www.grey-water-recycling.co.uk/
Rainwater harvesting website: http://www.ukrha.org/
17
EXTERNAL WATER CONSUMPTION
3.3. External Water Consumption
Approximately 13 % of domestic water consumption is via external
taps mainly for watering the garden but also for cleaning cars and
outside surfaces. Many non-residential buildings also use significant
quantities of water for maintaining their landscaped areas.
Rainwater could be collected to reduce the amount of mains water
used for these purposes as well as reducing the amount of water being
discharged into drains and watercourses, and the risk of localised
flooding and the overall water bills for householders and nonresidential users.
The simplest and most cost effective system for rainwater collection is
the water butt. This typically intercepts water from the rainwater down
pipes. More complex central collection communal systems, (using the
same principles as the water butt), are available for apartment blocks.
Collection of rainwater for use in the dwelling, e.g. for WC flushing, is
covered in section 3.2 above. If a rainwater harvesting system is
implemented for internal water use, external taps can also be supplied.
Water butts
Source: combinedharvesters.co.uk
18
EXTERNAL WATER CONSUMPTION
Code Credits
Wat 2 (External Potable Water Use) awards one credit for a correctly
specified system to collect rainwater for a garden, patio or communal
garden space. The size requirement for the potential maximum storage
of collected rainwater varies according to the size of the dwelling and
the type of garden space. Detailed specifications are provided for the
rainwater collector to meet the Code’s requirements for this issue.
Pools hot tubs or other large water-using features which are fed by
mains water, will automatically mean a score of zero for this issue.
This rule applies whether it is an internal or external pool. Where pools
are present, credits can only be awarded if the features use 100%
rainwater or 100% recycled water.
BREEAM Credits
There are no specific extra credits under BREEAM assessments for
rainwater recycling to supply outside taps for non-residential buildings.
Model Essential Requirement 3.3
The Council requires all residential buildings to achieve the credit
awarded for Wat 2 in the Code for Sustainable Homes.
The Council requires all non-residential and multi-residential
development (above 500 sqm of floorspace) with associated
landscape areas to design and implement a rainwater collection
system with storage of at least 1 litre/sqm of landscape area.
Compliance Check
Residential:
Code FSH Assessor’s reports at design stage and post construction
stage stating that the Wat 2 credit has been achieved.
Non-residential and Multi-residential:
19
EXTERNAL WATER CONSUMPTION
The developer to submit details of the amount of square metres of
landscaped area (private and communal gardens) associated with the
development or buildings as well the provided rainwater collection
storage capacity.
Sustainability Checklist
Q.3.3: How will the development’s landscape area be watered?
Planning Implications
Rainwater can be stored out of sight underground or directly under the
roof. On a domestic garden scale water butts are potentially more
visible if positioned on the street side of the building. The design of the
water butt can vary from typically green or black plastic to a more
rustic timber barrel. Large plastic butts can be unsightly and should
not be visible from the public realm, especially in conservation areas.
The detailed landscape design, if confirmed by a recognised ecological
consultant, could specify planting which requires little water in which
case the requirement for rainwater collection could be halved.
Further Guidance and References
Water UK, www.water.org.uk
UK Rainwater Harvesting Association (UKRHA), http://www.ukrha.org
CIBSE, Reclaimed Water (2004)
SEERA/Environment Agency, a Toolkit for Delivering Water Management and
Climate Change Adaptation through the Planning System (2005)
CIRIA, Guidance on the Integration of biodiversity and water attenuation, (2005)
WATER UK www.water.org.uk
UK RAINWATER HARVESTING ASSOCIATION (UKRHA) http://www.ukrha.org
20
REDUCTION OF SURFACE WATER RUNOFF
3.4. Reduction of Surface Water Runoff
Most of our streets, pavements and hard standings in the borough/city
have been built using impermeable surfaces. Consequently, existing
urban drainage systems have been constructed to remove the
collected rainfall from streets, pavements and hard standing areas to a
discharge point as rapidly as possible. The success of the system is
tempered by adverse effects, notably:
 Flooding – caused by a rapid concentration of rainwater into
discharge points.
 Pollution – many pollutants can be picked up with the surface
run off, subsequently causing ill effects at discharge points.
 Ground Water – the level of ground water can be depleted as
permeability is removed and rainwater is channelled away from
the point that it fell.
Principles of Sustainable Drainage
Drainage systems can be developed in line with the ideals of
sustainable development, by balancing the different issues that should
be influencing the design. Surface water drainage methods that take
account of quantity, quality and amenity issues are collectively
referred to as Sustainable Drainage Systems (SuDS). These systems
are more sustainable than conventional drainage methods because
they:





Manage runoff flow rates, reducing the impact of urbanisation on
flooding.
Protect or enhance water quality.
Are sympathetic to the environmental setting and the needs of
the local community.
Provide a habitat for wildlife in urban watercourses.
Encourage natural groundwater recharge (where appropriate).
They do this by:



Dealing with runoff close to where the rain falls.
Managing potential pollution at its source now and in the future.
Protecting water resources from point pollution (such as
accidental spills) and diffuse sources.
They may also allow new development in areas where existing
sewerage systems are close to full capacity, thereby enabling
development within existing urban areas. (Source: CIRIA)
21
REDUCTION OF SURFACE WATER RUNOFF
Sustainable Drainage Systems
The chief objective of a sustainable drainage system is to reduce the
rate of (or ‘attenuate’) the flow of surface water from roofs and hard
areas which would otherwise lead to problems of local flooding and
pollution. There are a number of attenuation methods which meet the
BRE criteria for achieving credits for surface water runoff in the Code
(Sur 1) and in the BREEAM assessments (Pol 7). These are:
Swales
Providing temporary storage and
passage of water, with some
filtration and infiltration potential,
these shallow vegetated surface
channels are very cost effective and
also provide landscape features. A
swale is often adjacent to roads, car
parks and residential areas. Swales
mimic natural drainage patterns by allowing rainwater to
run in sheets through vegetation. The vegetation helps
filter pollutants in the flow and swales may also permit
infiltration. If available, alkaline soils and sub-soils should
be used to promote the removal and retention of metals to
encourage good vegetation growth. Increasing the surface
area of the vegetation exposed to run-off improves the
effectiveness of the system.
Soakaways
Local or
centralised
soakaways either
as full systems or
as ‘overflow’ or
‘holding’ systems,
in areas where
local geological
and hydrological
conditions allow
them to
function. Confirmation
of approval from
relevant statutory
body needs to be
provided.
22
A modern soakaway using
modular attenuation cells
REDUCTION OF SURFACE WATER RUNOFF
Green Roofs
Permeable
Paving
Using the appropriate plant types, these roofs can limit
discharge into drains as well as provide an element of
filtration. For soil based grass roofs, calculation should be
made on the basis of the infiltration, moisture retention
and depth of soil. For sedum roofs, infiltration data should
be provided by the manufacturer/installer.(see section 7.0
(Green Roofs)
Porous ground cover can reduce or remove the need for
drains and sewers, as well as maintaining ground water
levels in areas where local geological and hydrological
conditions allow this to function, e.g. block paved surface
on permeable sub-base over gravel bed to store the water
and allow it to seep in to the soil. For less-permeable soils
the gravel layer might be deeper and the water taken to a
soakaway although this is not an option in some areas.
Roads, footways and carparks can be paved with either
porous blocks
or with blocks which allow infiltration of water through
their joints.
Porous asphalts and macadams are also being trialled.
One major disincentive for employing permeable paving is
its limited lifespan. After perhaps 10 years (depending on
conditions) the paving becomes increasingly impermeable
and the only solution may be to relay the surface
completely.
Infiltration
Trenches and
Filter Drains
Basin
Rainwater
Harvesting
Similar structures to one another, the infiltration trench
provides water storage and infiltration through a stonefilled trench. A filter drain filters water through soil into a
perforated underground pipe, providing more storage and
some infiltration.
Basins initially retain storm water, before a process of
filtration and infiltration through the underlying rocks.
Run-off from roofs is collected as a part of a rainwater
harvesting system
23
REDUCTION OF SURFACE WATER RUNOFF
Ponds and
Wetlands
As part of a wider infrastructure of SUDS, ponds and
wetlands can be designed specifically – by means of
intended capacity and planting – to increase storage
capacity and provide a high quality filtering system.
When systems are used to collect run-off from vehicular areas or other
areas which are subject to potential pollution risks, they must be
covered by appropriate pollution control measures such as interceptors
etc. Specialist advice should be sought from relevant statutory
authorities on what is appropriate in such instances.
The effectiveness of SuDS type systems will depend on many factors,
including run-off rates, ground conditions and topography in relation to
size, type and density of the development. It is therefore important
that SuDS are designed to match local geological and hydrological
conditions.
There is a potential conflict between the aspirations to increase
infiltration of rainwater into the ground on brownfield sites where this
rainwater could leach contaminants. This could be addressed by
buffering the flow of rainwater with tanks, in a similar way that storm
water is dealt with from motorways or by the use of green roofs.
Case studies
Use of Sustainable Drainage (SuDS) – Bognor Regis Sports Centre
A sports centre constructed in 1999, which is owned and operated by West Sussex
County Council. It includes synthetic sports pitches, a multi-use games area and
parking for 136 cars.
The total size of the site is approximately 2 ha and the capital value of the scheme
was £2.5 – 3M. The main SuDS used in the scheme are:
• Porous paving has been used in the roads and areas of car parking allowing blanket
infiltration.
• An infiltration trench has been incorporated accepting the pitch drainage.
The scheme works with the sports centre roof and paved areas draining into the
porous car parking area. The drainage of both the car park and sports pitches are
connected to an infiltration trench that runs along the side of the road. When heavy
24
REDUCTION OF SURFACE WATER RUNOFF
rain is experienced, excess water flows are stored in the pitch under-drains and the
car park sub-base.
The benefits of the scheme are:
• Reduced flood risk.
• Promotion of ground water recharge.
Code credits
There is a mandatory requirement that the development must not
make the runoff situation worse than before development.
There are two possible Code credits under Sur1 (Management of
Surface Water Runoff) for using SuDS and establishing management
agreements for their long term maintenance.
BREEAM credits
One credit is awarded under Pol 7 in BREEAM assessments:
‘Where evidence provided demonstrates that Sustainable Urban
Drainage techniques are specified to minimise the risk of localised
flooding, resulting from a loss of flood storage on site through
development.’
Model Essential Requirement 3.4
The Council requires all residential development to achieve
both Sur1 Code For Sustainable Homes credits
and
all non-residential and multi-residential development (over 500 sq m of
external floor space) to achieve:
the Pol 7 BREEAM credit
Compliance Check
Residential:
Code FSH Assessor’s reports at design stage and post construction
stage stating that both the Sur 1 credits have been achieved.
Non-residential and Multi-residential:
25
REDUCTION OF SURFACE WATER RUNOFF
BREEAM Assessor’s reports at design stage and post construction stage
stating that the Pol 7 credit has been achieved.
Sustainability Checklist
Q.3.4: What Sustainable Drainage Systems will be employed to
attenuate storm water runoff from the development’s roof areas and
areas of hard standing?
Planning Implications
Many of the SUDS measures, such as swales, basins and balancing
ponds can be incorporated into the development’s surrounding
landscape. They can also benefit the biodiversity of the site by creating
new habitats. They can be positive assets but only if they are properly
designed as part of that landscape and are appropriate to the site
context and the development.
The measures that require large areas of surface area, such as ponds
and basins, reed beds and swales may not be appropriate or feasible in
high density developments. Where space at ground level is limited,
soakaways, permeable hard surfacing and green roofs may be more
appropriate design solutions.
It is essential that SuDS are properly maintained to ensure their
successful operation. Where SuDS are proposed, legal agreements for
their maintenance, or agreed acceptable alternatives, must be secured
and approved by the Council.
The Government is currently consulting on proposals to make SuDS
mandatory for new development and to make Local Authorities
responsible for their long term maintenance.
Further Guidance and References
BRE, Digest 365:1991 and BS EN 752-4 contain guidance on calculating the peak
flow rate and determining the design flooding frequency
The Met Office (incl. figures for UK rainfall), www.met-office.gov.uk
British Standards Online, http://bsonline.techindex.co.uk/
The Environment Agency, www.environment-agency.gov.uk/
26
REDUCTION OF SURFACE WATER RUNOFF
DEFRA, www.defra.gov.uk
BRE, Soakaway design (Digest 365, 1991)
BRESOAK, Soakaway design software (2007)
CIRIA, Sustainable urban drainage systems – best practice manual for England,
Scotland, Wales and Northern Ireland (CIRIA Publication C523) (2001)
BS EN 752-4, Drain and sewer systems outside buildings – Hydraulic design and
environmental considerations (1998)
BS EN 12056-3, Gravity drainage inside buildings – Roof drainage, Layout and
Calculations (2000)
British Council of Offices and Corporation of London, Green roofs – research
advice note (2003)
Mayor of London and AUU, Living roofs (2004)
www.london.gov.uk/mayor/auu/livingroofs
Scottish Environment Protection Agency, Environment Agency, Environment
and Heritage Service, Sustainable Urban Drainage Systems: an Introduction
(2003)
National SUDS working group, Interim code of practice for SD Systems (2005)
CIRIA, Source control using constructed pervious surfaces – hydraulic, structural
and water quality performance issues (CIRIA Publication C582) (2001)
CIRIA, Sustainable Urban Drainage Systems: design manual for England and Wales.
(CIRIA Publication C522) (2000)
Environment Agency, Pollution Protection Guidelines, General Guidelines to the
Prevention of Pollution (2003)
27
FLOOD RISK
3.6. Flood Risk
Principles
Space for new development in England is limited but no one wants to
live or work in a house or business that is at risk of flooding. Coastal
flooding is predicted to be an increasingly
serious problem with a combination of more
severe weather events and rising sea levels
caused by climate change. It is also predicted
that peak river flows during the next 100 years
will increase by 20%.
In the adopted Planning Policy Statement 25
(PPS 25) the government has provided guidance
to help planners manage flood risk and direct
development to locations least likely to flood The
PPS is a material planning consideration that
local planning authorities must take into account
when considering planning applications. PPS 25
requires all local planning authorities to include a sequential test for
flood risk in their development plans. This sequential test is based on
the Environment Agency’s flood zone mapping, which divides all land
into three zones according to the risk of flooding. A Strategic Flood
Risk Assessment (SFRA) will support this test. The Government has
also produced a supporting practice guide currently published as
“Living Draft” to provide practical advice on a number of topics,
including flood risk assessment. This is presently due as a final issue in
May 2008.
Strategic Flood Risk Assessment (SFRA)
The SFRA is a tool to facilitate a strategic approach to reducing flood
risk throughout the Borough/City. It will become a powerful driver for
sustainable development through a sequential approach to allocation
of development in decreasing order of flood risk. It identifies flood risk
across a variety of sources and incorporates the predicted effects of
climate change.
The Environment Agency produce flood zone maps which identify the
level of risk of flooding without the presence of defences, the zones
are as follows:
28
FLOOD RISK
Flood Risk Level
Zone
1
Little or no risk of flooding
2
Medium risk of flooding
3
High risk of flooding
Numerical Risk
(1 in 1000 chance (0.1%)
or less in any year)
(1 in 1000 to 1 in 200
chance (0.1% - 0.5%) in
any year for tidal flooding)
(1 in 1000 to 1 in 100
chance (0.1% - 1%) in any
year for river flooding)
(1 in 200 chance (0.5%)
or greater in any year for
tidal flooding)
(1 in 100 chance (1%) or
greater in any year for
river flooding)
A SFRA has been produced for the PUSH sub region and provides a
snapshot of flood risk issues including climate change and flood
defence asset information available in 2007. The SFRA highlights the
probability and hazards of flooding for areas of land throughout the
Borough/city.
One of the main reasons for carrying out SFRAs is to inform the
process of the sequential test on flood risk set out in PPS 25, which
requires that land at lowest risk be developed first. The Exception Test
is only appropriate when there are large areas in Flood Zones 2 and 3,
where the Sequential Test alone cannot deliver acceptable sites. This is
where some continuing development is necessary for wider sustainable
development reasons, or where landscape, heritage and nature
conservation designations, eg Areas of outstanding Natural Beauty
(AONBs), Sites of Special Scientific Interest (SSSIs) and World
Heritage Sites (WHS), prevent the availability of unconstrained sites in
lower risk areas.
Any proposals for development in EA flood zones 2 and 3 and any site
greater than 1hectare require a Flood Risk Assessment (FRA) This
looks at the safety of a proposed development and its potential impact
on surrounding areas using more detailed scenarios.
29
FLOOD RISK
Mitigation Measures
When constructing new properties permanent flood resistant measures
are always preferable to temporary measures. Notwithstanding the
sequential approach to allocating development away from areas at risk
of flooding, it is essential that new developments which are proposed
within flood risk areas are safe and that new developments are
designed and constructed such that the health and safety and welfare
of people is appropriately managed. Climate change should also be
taken into account by adopting a precautionary approach and ensuring
development can be adapted and managed to deal with impacts from
climate change.
If building in flood risk areas cannot be avoided there are practical
strategies and designs which can be implemented. None of these are
guaranteed to fully prevent flooding or its associated risks:
These are also important when considering how to increase the
resistance and resilience of existing communities and property to the
effects of flooding.
There is a key requirement that drainage is designed to retain water
onsite and reduce detrimental effects of rapid surface water runoff on
downstream catchments. The implementation of Sustainable Drainage
Systems (SuDs) should be an important component of new
development (see Issue 3.5 above (Surface water Runoff and
Flooding)).
A site on the edge of Flood Zone 2
30
FLOOD RISK
Some Practical Design Measures for Mitigation










Ground and floor levels could be raised.
Site layout is important and the incorporation of flood escape
routes that are publicly accessible with clearly displayed and
well-maintained signs is essential. Vehicular access during flood
condition will also normally be required. Developers should
ensure that appropriate evacuation and flood response
procedures are in place to manage the residual risk associated
with an extreme flood event.
Culverted watercourses should be restored to open channels
wherever practical.
Single storey residential developments should not normally be
considered in flood risk areas.
Landscaping can be used to direct or divert floodwater away
(e.g. earth bunds) unless this increases flood risk elsewhere.
Pumps may be required.
Boundary walls and fencing could
be designed using high water
resistance materials (e.g. solid
gates with waterproof seals).
Resistance and resilience should be
incorporated into design of
buildings and the use of sacrificial
materials should be considered
Example of property boundary wall and lower
both internally and externally.
sealed gate (courtesy of Severn Trent water)
The likely velocity of floodwater
(DCLG).)
should also be assessed as this
could be a danger.
Surface water and foul drainage
systems, should satisfy the
requirements of the 6th edition of
sewers for adoption.
If there are adequate warning
A swale as part of SUDS in a new housing
systems in place it may be
development (courtesy of HR Wallingford)
reasonable to locate parking or
Ltd.)(DCLG)
other flood compatible uses at ground floor level and people
intensive uses above.
31
FLOOD RISK
The construction of new flood defences to enable development to take
place in flood risk areas should be avoided as the remaining residual
risk behind flood defences are high. In the instance of river flooding
creation of washlands or compensatory flood storage areas should be
provided where necessary.
In order to decide which resilient measure would be effective it is
necessary to know the potential depth and duration of flooding that is
likely to occur. Figure x summarises the overall rationale behind the
design strategies.
Rationale for flood resilient and/or resistant design strategies
Avoidance
Resistance/resilience**
Design Water
Depth*
Mitigation Measures
Approach
Design Water
Depth
above 0.6m
Allow water through
property to avoid risk
of structural damage.
Attempt to keep water
out for low depths of
flooding ‘Water Entry
Strategy’ ***
• Materials with low
permeability up to
0.3m
• Accept water passage
through building at
higher water depths
• Design to drain water
away after flooding
• Access to all spaces
to permit drying and
cleaning
Design Water
Depth
from 0.3 to
0.6m
Attempt to keep water
out, in full or in part,
depending on
structural assessment.
If structural concerns
exist follow approach
above ***
Materials with low
permeability to at
least 0.3m
• Flood resilient
materials and
designs
• Access to all
spaces to permit
drying and cleaning
Design Water
Depth
up to 0.3m
Attempt to keep water
out ‘Water Exclusion
Strategy’
• Materials and
constructions with low
permeability
Remove
building/development
from flood hazard
• Land raising,
landscaping,
raised thresholds
32
FLOOD RISK
Notes:
* Design water depth should be based on assessment of all flood types that can
impact on the building
** Resistance/resilience measures can be used in conjunction with Avoidance
measures to minimise overall flood risk
*** In all cases the ‘ water exclusion strategy’ can be followed for flood water depths
up to 0.3m
It should be noted that these mitigation measures cannot be used to
justify development in areas of high flood risk. They are to be
employed when the relevant tests have been passed and the
development’s location is agreed to be unavoidable in a high risk flood
zone.
Code credits
There are two possible Code credits under Sur 2 (Flood risk) if the site
is in zone 1. A single credit is available for a zone 2/3 development
that includes certain attenuation measures.
BREEAM credits
There is the potential for three credits in Pol 5 (Minimising flood risk)
depending on the level of flood risk and with the requirement for
SuDS.
Model Essential Requirement
None as already a requirement under PPS25
33
FLOOD RISK
Sustainable Checklist
Q.3.5: Is the proposed development in accordance with PPS 25?
Planning Implications
Any application for development within flood zones 2 and 3 will need to
be accompanied by a Flood Risk Assessment (FRA) which will assess
flood risk and its potential impact on surrounding areas using more
details of the local area than those covered within the high level SFRA.
There should also be a demonstration that there are no reasonable
options available in a lower flood risk category. The FRA should also
assess the surface water and drainage of the area. The sequential test
should be applied within the development sites themselves.
Removal of permitted development rights could be used where
permitted development threatens to have a direct significant and
adverse effect on a flood risk area or its flood defences and their access,
or the permeability and management of surface water, or flood risk to
occupants.
Mitigation measures are likely to have a visual impact on the external
appearance of the development and may also influence building height
and internal layout.
Case Study
An example of FLOWS Demonstration site.
The Lamb Drove project was run by Cambridgeshire County Council as
part of the Flows project. This is located on the southern side of
Cambourne, a new settlement approximately eight miles west of
Cambridge, and comprises 35 dwellings on a one hectare site. Through
an integrated system of
sustainable drainage
features, the site brought
environmental, ecological
and social benefits to
residents. Implementation
of SuDS included
permeable paving,
34
FLOOD RISK
detention basins, swales, green roof, water butts and flood proofing.
Detention basin at Lamb Drove development, Cambridgeshire (image courtesy of Royal
Haskoning)(Planning Policy Statement 25: Development and Flood risk Practice guide
Pg 78.)
Further Guidance and References
DTLR Preparing for Floods February 2002
http://www.odpm/stellent/groups/odpm_buildreg/documents/page/
odpm_breg_600451.pdf
Association of British Insurers Strategic Planning for Flood Risk.
July 2004 www.abi.org.uk
EBC Eastleigh Borough Councils Strategic flood Risk Assessment
http://www.eastleigh.gov.uk/ebc-1479
Governmentguidance Improving the flood performance of new buildings. Flood
resilient construction.
http://www.planningportal.gov.uk/uploads/br/flood_performance.pdf
Planning Policy Statement 25: Development and Flood risk Practice guide:
http://www.communities.gov.uk/publications/planningandbuilding/pps25practiceguide
Environment Agency advice:
http://www.environment-agency.gov.uk/homeandleisure/floods/default.aspx
35
ADAPTATION TO CLIMATE CHANGE (WATER)
3.6. Adaptation to Climate Change (Water)
Water Resources
Changing patterns of rainfall will have a significant impact on water
resources and water quality. In the summer, warmer temperatures will
mean that demand for water grows just as supply – especially in water
in rivers and underground aquifers – declines due to lower rainfall.
Urban areas have little capacity to store drinking water and are more
likely to experience shortages during droughts.
The following actions and techniques should be employed at a
neighbourhood or building level to manage increased pressures on
water resources:








Rainwater harvesting (See Issue 3.2).
SUDs to store and collect water (See Issue 3.4).
Grey water recycling (See Issue 3.2).
Xeriscaping, low water use
planting can greatly reduce
water demand. The main
principles of this landscape
technique are as follows:
o Select plants with
some drought
resistance, including
grass varieties.
o Ensures soils well
mulched.
o Design the most
efficient irrigation system for the planting
o Maintain and manage properly to reduce future water
stress
Effective storm overflow management prevents surface water
contamination.
Managing point source pollution reduces water quality risks.
Water efficient appliances (See Issue 3.1).
Green Roofs (See Issue 7.1).
Flooding
Rising sea levels, increases in average winter precipitation and in
the frequency, duration and intensity of heavy downpours will increase
36
ADAPTATION TO CLIMATE CHANGE (WATER)
flood risks. Impervious surfaces in urban areas will exacerbate
the risks by preventing rainwater from percolating into the ground.
Efforts should focus on understanding and managing flood pathways
and protecting areas at risk. The following actions and techniques
should be employed at a neighbourhood or building level to manage
increased flood risk:
• Strategic flood risk assessment and a sequential approach to
development in the floodplain (See Issue 3.5).
• Impermeable surfaces can be replaced by SUDS (See Issue 3.4).
• Smaller scale hard barriers or managed realignment schemes.
• A second layer of setback flood defence constructed behind the
original barrier. This is often used with managed realignment.
• Use of green open space and green roofs to reduce runoff and
ameliorate pressure on drainage systems during heavy rainfall. (See
Issue 7.1).
• Widening drains to increase drainage capacity.
• Managing flood pathways and removing ‘pinchpoints’ so that heavy
rainfall can drain away.
• One way valves permanently fitted in drains and sewage pipes to
prevent backflow and, as a last resort, widening drains to increase
capacity.
• Flood resilient measures, including raising floor levels, electrical
fittings and equipment; rain proofing and overhangs to prevent
infiltration of heavy rain around doors and windows; temporary
free-standing barriers which hold back floodwater from properties.
• Flood resilient materials can withstand direct contact with
floodwaters for some time without significant damage. These include
concrete, vinyl and ceramic tiles, pressure-treated timber,
glass block, metal doors and cabinets.
• Removable household products like flood boards, air brick covers and
flood skirts which are fitted temporarily to properties to form a barrier
to water. Pipes, drains and toilet bowls can be temporarily blocked
using an expandable/inflatable bung to prevent backflow. In cases of
severe flooding, the stress caused by water volume can damage the
structure and foundations of buildings, making it more harmful to keep
water out than to let it in.
Code Credits
Many of the measures outlined above will, if successfully implemented,
also reward the developer with credits in a number of issues. These
include: Wat 1 and Wat 2 and Sur 1 and Sur 2.
37
ADAPTATION TO CLIMATE CHANGE (WATER)
BREEAM Credits
Many of the measures outlined above will, if successfully implemented,
also reward the developer with credits in a number of issues. These
include: Wat 1 & Wat 5 and Pol 5 & Pol 6.
Case Studies
Model Essential Requirement
The Council will require all planting associated with all residential
development and all non-residential and multi-residential
development above 500 sq m to be selected for resilience to
summer drought
Compliance Check
The proposed landscape must meet with the approval of the Council’s
landscape architect for resilience to expected climate change.
Sustainable Checklist
Q3.7: What measures are included in this development to adapt to
conditions of increased water resource stress and greater flooding
risk?
Planning Implications
Well designed adaptation can have additional benefits for water quality
and enhance public spaces. Where green space, either at ground or
roof level has an additional water management function, this can help
provide greater justification for such areas. Measures to ‘floodproof’
buildings will need careful design scrutiny to ensure that they do not
create unattractive ground floor level environments.
Further Guidance and References
DEFRA, Climate Change impacts and adaptation: Cross-Regional Research
Programme,
www.defra.gov.uk/environment/climatechange/uk/adapt/crossreg.htm
38
GLOSSARY (WATER)
GLOSSARY
‘Residential’ refers to all new houses and flats but not to extensions
and conversions.
‘Multi-residential’ refers to institutional accommodation such as
student halls of residence or sheltered housing for the elderly
‘Non-residential’ refers to all other building uses such as offices,
retail buildings, schools, industrial buildings etc.
39