Aggregate Industries’ Flood Risk Assessment says:
The development lifespan will be 10 to 12 years, so it is proposed that an allowance for a 10% increase in extreme rainfall is considered, according to NPPF guidance on climate change which states that an allowance of 10% is made for development with a lifetime extending to 2039 respectively;
The change to the landform would not, however, be for just 10 to 12 years – it would be FOREVER.
In our response in 2017, we wrote:
114. The applicant has used an uplift of +10% in its runoff calculations to reflect climate change. However, since this proposal would result in a permanent change upon the landscape this uplift is inadequate. The EA forecasts peak rainfall intensity increasing by 20% in 2055-2085 and 30% in 2085-2115.
We pointed to the LLFA’s response to Aggregate Industries’ ROMP application for Hillhead, which said:
Following the publication of the Flood Risk Assessments: Climate Change Allowances document (dated 19th February 2016) by central government, the applicant will be required to use a climate change uplift value of 40% when sizing the proposed surface water drainage management system for this development.
40%, not 10%.
In May this year, Devon County Council's Flood Risk Team, in its role as Lead Local Flood Authority, objected to Aggregate Industries' proposal, but was comfortable with what it understood to be the allowance for climate change:
In terms of the concerns relating to climate change, the applicant has proposed a surface water management strategy which includes an allowance of 40% for climate change in terms of rainfall within the attenuation calculations. This is inline with the most up to date guidance from the Environment Agency: Flood Risk Assessments - Climate Change Allowances (July 2020).
Which would be brilliant – if 40% were true. The LLFA had either misread, or not read, Aggregate Industries' FRA. We wrote to the LLFA pointing out the discrepancy in their understanding.
Nevertheless, the LLFA has since withdrawn its objection, obviously still comfortable with the uplift for climate change even though it is only 10%. The statutory consultee pointed to the access road and holding area, and to national policy:
The applicant has provided calculations to indicate that the proposed surface water drainage system for the access road and holding area has been designed to manage the 1 in 100 year event plus climate change which is in line with local and national policy.
Indeed, the access road and holding area may have a more limited lifetime, for which drainage calculations may be in line with national policy, but what about the 56 or more acres that would be permanently changed?
National policy considers the lifetime of development in terms of flood risk, and says:
The lifetime of a non-residential development depends on the characteristics of that development. Planners should use their experience within their locality to assess how long they anticipate the development being present for. Developers would be expected to justify why they have adopted a given lifetime for the development, for example, when they are preparing a site-specific flood risk assessment. The impact of climate change needs to be taken into account in a realistic way and developers, the local planning authority and Environment Agency should discuss and agree what allowances are acceptable. Paragraph: 026 Reference ID: 7-026-20140306
National policy also says:
Indeed, for Aggregate Industries' proposal to construct an asphalt plant at Hillhead, the LLFA specified:
MicroDrainage model outputs will be required to demonstrate that the proposed surface water drainage system is designed to the 1 in 100 year (+40% allowance for climate change) rainfall event.
So why – when a 40% uplift was required at Hillhead for both the quarry and the asphalt plant, and when flooding has been acknowledged as such an important issue for communities downstream of Straitgate Farm – did the LLFA in all its flooding wisdom think that a 10% allowance for climate change would be acceptable, for a development that would not only leave a PERMANENT scar on the landscape, but would also PERMANENTLY change the way surface water runs off the site?
Has the LLFA not seen the news this year, the death and destruction that can happen when 150 mm of rain falls in 24 hours?
