Committee on Climate Change
7 Holbein Place
London SW1W 8NR
Mary Creagh MP
Chair, Environmental Audit Committee
House of Commons
London
SW1A 0AA
31 March 2017
Dear Mary,
RE: Questions arising from climate change adaptation evidence session
I am writing to follow up on two questions that arose during the evidence session on
Tuesday 14th March. We were asked for a list of those organisations that declined to
take part in the second round of reporting under the Adaptation Reporting Power (ARP)
in the Climate Change Act. We were also asked about the benefits of green roofs.
 Annex A provides a list of the 21 organisations that decided not to take part in
ARP round 2. It also lists the seven organisations that indicated they would report
but have so far not done so.
 Annex B provides an overview to the benefits of green roofs and other types of
sustainable drainage systems (SuDS).
You might like to note that today the Adaptation Sub-Committee has published its
advice to Defra on the third round of ARP reporting. The report can be found on the
CCC͛ν Ϯ̼͋νΊχ͋΄ https://www.theccc.org.uk/publications/
If you would like further information in either of these areas I would be pleased to assist.
Yours,
MATTHEW BELL
Chief Executive, Committee on Climate Change
1
ANNEX A: Participation in Adaptation Reporting Power round 2 (ARP2)
Defra's focus for ARP2 was to ensure that the reporting process was more flexible, light touch
and responsive to the needs of reporting authorities. There was therefore greater freedom in
how organisations reported in Round 2, as well as the option to not report at all. Table 1 shows
that a number of water companies, as well as national parks and others, decided not to report in
Round 2. The table reflects the reports received before the end of February 2017. Those
organisations shown in italics were invited to take part in Round 2 for the first time.
Table 1. Overview of reports in ARP1 and ARP2
Organisations
Number reported in ARP1
105
Number invited and reported in
ARP2
114 in scope in total, 111 were invited to report, 86 have reported
Of the original 114, three declined at consultation time, 18 have
declined since being invited, and seven may still report.
Four of those not reporting were due to take part in ARP2 for the first
time (shown below in italics).
Declined to participate in ARP2
at consultation time (3)
Harwich Port, NATS, Office of Rail and Road (was Office of Rail
Regulation at the time of the consultation)
Declined after ministerial
invitation (11)
Sheerness Port, Mersey Docks, Eurotunnel, ES Pipelines, Bristol Water,
Exmoor National Park, Dartmoor National Park, Yorkshire Dales
National Park, Canals and Rivers Trust, Cardiff Airport, Edinburgh
Airport
Withdrew after initially saying
they would report (7)
Brookfield Asset Management, Luton Airport, Northumbrian National
Park, North York Moors National Park, Chief Fire Officer's Association,
Church of England, New Forest National Park
Organisations that may still
report (7)
Essex and Suffolk Water, Northumbrian Water, BT, South West Water,
Sutton and East Surrey Water, Ofcom, Greater London Authority.
Of these Essex and Suffolk Water, and Northumbrian Water, are due
to report late, by March 2017.
Source: Defra.
Notes: Numbers are based on organisations reporting and not the number of reports, as some
organisations reported jointly. Organisations in italics were invited to report for the first time as part of
ARP2. Correct at the end of February 2017.
2
ANNEX B: Effectiveness of green roofs and storage tanks in attenuating surface water
CIRIA͛ν ̽Ϊ΢ζι͋·͋ΣνΊϭ͋ SuDS manual updated in 2015 provides full details on the effectiveness of
SuDS in reducing peak flows and volumes (i.e. providing surface water flood attenuation). It
explains the difference between ·νΪ͕χ͛ ΋ϢD΋ νϢ̽· ̯ν ͽι͋͋Σ ιΪΪ͕ν ̯Σ͇ ··̯ι͇͛ ΋ϢD΋ νϢ̽· ̯ν
underground storage tanks.
SuDS schemes are designed to be able to retain certain volumes of water and to release it slowly
into the environment or the drainage network΅ Α·Ίν ι͇͋Ϣ̽͋ν χ·͋ ·ζ̯͋Ι ͕ΜΪϮ͛ during the storm
event and therefore reduces the chance of surface water flooding. The capture and slow release
of rainfall Ίν ̯̽ΜΜ͇͋ ·̯χχ͋ΣϢ̯χΊΪΣ͛΅ HΪϮ͋ϭ͋ι΂ ̯ν with all the flood alleviation measures, the
positive impact of SuDS decreases for events that exceed their design capacity. Defra͛ν nonstatutory SuDS technical guidance suggests that SuDS should be designed to manage peak flows
and volumes corresponding to those with 1 in 100 chance of occurring in the equivalent
greenfield site in any given year (where reasonably practical).
Green roofs (as well as other soft SuDS) also help reduce run-off overall because the plants use
up some, and some is also released through evaporation. T·Ίν ·ΊΣχ͋ι̽͋ζχ͇͋͛ ϭΪΜϢ΢͋ Ίν ϢνϢ̯ΜΜϴ
small, but helps reduce the total amount of water reaching drains and water bodies. This is one
Ϊ͕ χ·͋ ̯͇ϭ̯Σχ̯ͽ͋ν χ·̯χ ·soft͛ ΋ϢD΋ ζresent Ϊϭ͋ι ··̯ι͇͛ ΋ϢD΋΂ together with many others including
helping with water and air quality, biodiversity, and moderating internal building temperatures
and the urban heat island. The non-statutory technical standards published by the Welsh
Government specify that the first 5mm of any rain event should be intercepted. 50% of all
rainfall events are of less than 5mm, and the first 5mm of a rain also is the most polluted when it
runs off roads and hard surfaces. Preventing this first 5mm entering drains and water courses is
therefore important. This is one of the many reasons why the Welsh SuDS guidance is superior
to Defra͛ν, which does not include any guidance on interception volumes.
Lastly, it should be noted that new evidence compiled independently for the Welsh Government
found that the capital costs of νΪ͕χ ·landscaped͛ SuDS solutions are lower than the costs of
comparable conventional solutions. On average, the analysis suggests that the use of SuDS could
reduce overall construction costs by £9,000 per new home. The maintenance and operational
costs of SuDS were also found to be lower amongst the development sites considered.
The Welsh Government has stated that they are now considering whether to commence
Schedule 3 of the Flood and Water Management Act.
3