Water masterplanning and drainage design in the UK. Problems, issues and challenges.

1. INTRODUCTION, FAILURES AND SUCCESSES

2. Surface water drainage systems developed in line
with the ideals of sustainable development and
address the consequences of climate change.
They are collectively known as SUDS.
They are being implemented right across the
world as the importance of water increases
(excluding permafrost regions).
They are designed to:
Manage the environmental risks resulting
from Urbanisation
Contribute to environmental enhancement.

3. Minimisation of the impact from the development on the quality
and quantity of the runoff and maximise amenity and
biodiversity opportunities.
The extent to which this is possible depends on the site, but the ideal is they have
equal standing. All SUDS systems needs to have at least 2 of the 3 elements:
Amenity &
Biodiversity
Quantity Quality

4. Enhancing Reduce run Reduce run off
biodiversity off rates volumes
Enhanced
amenity and What ARE WE TRYING
TO ACHIEVE?
aesthetic value
Reducing pollutant Encouraging
concentrations and a groundwater recharge
buffer mechanism

5. What does not count as SUDS?
Giant tanks with impermeable liners
NO VOLUME REDUCTION – NO GROUNDWATER RECHARGE
NO WATER TREATMENT – NO ECOLOGICAL AND NO
BIODIVERSITY VALUE
MOST DRAINAGE DESIGN PRE 1990

6. PEAK ATTENUATION REDUCTION
Without attenuation
Flow
(m3/s)
With attenuation
Time

8. EU Water Buildings Flood Water
Framework Regulations various Management Act
Directive 20/60/EC amend. 2010
Water Industry Act Various other Water Groundwater
1991 Bills Regulations 1998
Land Drainage Act Water Resources
1991 Act 1991

9. • Soakaways, Swales, permeable
Discharge to
groundwater block paving and other source
control
Discharge to • EA or LDA approval and
watercourse controls
Discharge to
• Automatic right
surface water sewer
removed
Discharge to
combined sewer

10. If you can’t infiltrate at
all then harvesting is
Must treat
likely to be necessary first 5mm
In public highways
Or public areas, not
back gardens
Not onerous, but
sensible and Adoptable
practical Minimum Located in
construction standards accessible
standards location
2013
Early
Appointment of experienced engagement
Drainage Impact / Drainage
Civil Engineer very early in prior to Strategy Reports necessary
project planning as per Scotland

11. Problems included:
 Very low infiltration
 No surface water sewer within 80m
 No watercourses within 200m
High groundwater level (seasonal)

12. Rainwater
Maximising Source Garden
control techniques Quantity
and wetted Amenity
Biodiversity
perimeter
Health
Landscaping
swale
Attenuation
Biodiversity Porous
Asphalt
Permeable
block
Paved Car
Parks
Quality
Quantity

13. Small internal courtyard
RWPS
High level overflow
Attenuation to public sewer
crates
Fountain pump Storm water
storage

14. Residential flats with underground car park
RWPS from roof
Flats
Car park flow Basement
To foul sewer
Boundary
Impermeable
ground Storm water attenuation and
separation prior to borehole

15. Stephen Gibson, Director – Wilsham Consulting
E stephen@wilsham.co.uk
T 01235 529646
M 07449948261
W www.wilsham.co.uk
Wilsham provide civil engineering professional services across a
very wide spectrum of developments, from hotels, private luxury
houses, estate water master-planning, churches, water companies,
cathedrals, schools and health facilities.
This includes:
• FRAs, Residential and commercial estate water master-planning,
• Drainage Impact / Strategy Reports to support SAB applications
• Highway Design,
• Waste water design,
• Groundwater and flood mitigation
• Engineering advice to water company legal groups