WYG's technical director Matthew Elliott describes how the Liverpool Waters development is considering the impacts of a changing climate
The Liverpool Waters vision involves regenerating a 60-hectare historic dockland site to create a high-quality, mixed-use waterfront quarter in the city centre. It is located on the east of the River Mersey estuary and work on the site is due to start later in the year, with completion by the 2040s.
Peel Holdings’ 30-year development timeframe means that climate change adaptation was a key consideration in preparing the environmental impact assessment (EIA) for the site. A particular challenge was considering the impacts of sea-level rise over the duration of the development, and beyond.
Rising seas
Given the long lifetime and high cost of the built environment, it is imperative that plans and investment projects take into account the changing risks over the coming 100 years or more. Sea levels have been generally rising since the end of the last Ice Age, but in the UK the movement of the land complicates forecasting future sea levels. Basically, the South East of the UK is sinking faster, relative to mean sea level, than the North West.
There is now evidence to indicate that climate change is accelerating the rate of ice depletion in the Arctic and pushing up average global temperatures to such an extent that the long-term rate of rise in sea level around the UK is faster than previously anticipated.
To these figures it is necessary to add the effects of potentially increased storminess, which augments wave heights, and storm surge, where water is forced into estuaries and onto the coast by sustained strong winds, together with the effect of low atmospheric pressure. As a result, water levels can occur considerably above those which would be expected on account of astronomical tide levels alone. Clearly, the situation is highly complex.
The various climate change model scenarios set out in the UK Climate Projections 2009 (UKCOP09) take account of a range of political decisions and global economic growth over the next century. These will influence the likely human impact on average sea levels that will prevail in Liverpool in 100 years’ time, and the allowances that should be made for potentially higher waves and surge.
What these show is that there is considerable uncertainty as to the predicted levels that can be most appropriately dealt with by a “managed adaptive approach” – that is, to invest now in actions that manage today’s risks, but keep options open so better decisions can be continually made over the whole life of investments.
This issue has been a particular concern for Liverpool Waters because of the need to preserve the heritage assets of the former docklands, part of which is a World Heritage site, and means that alteration of these highly significant features has to be avoided.
Retaining heritage
The overall approach to the Liverpool Waters development has been to retain the remaining historic dockland surface features that are of heritage significance. Historic buildings will be carefully conserved to incorporate resilience and land uses appropriate to the future flood-risk exposure.
For the proposed new buildings, minimum finished floor levels have been specified in the flood-risk assessment supporting the EIA. Also, there is a requirement that any residential occupation is at first-floor level or at such a level that future flood risk will not become a problem. Typically, levels are set to be above the one-in-200-years flooding level, including an assessment of climate change increases in sea level, as recommended by Defra. These figures take account of the climate change scenarios modelled in UKCOP09.
The option to use property-level protection, such as flood barriers for doors, has not been discounted and remains part of the overall managed adaptive approach. Future access and egress arrangements during a flooding event are considered as part of this approach as it is essential that, in such circumstances, vehicular access can be maintained to properties. It has therefore been necessary to consider the creation of routes that do not conflict with the historic features requiring preservation.
Timeframe
The longevity of the development phase and subsequent occupation presents a real challenge to the redevelopment of many prime coastal waterfront locations in the UK. However, by adopting a managed adaptive approach, appropriate development specification can be provided to ensure ongoing flexibility, so future levels of protection will not be prejudiced, while at the same time it will preserve the important heritage assets.
This article was written as a contribution to the EIA Quality Mark’s commitment to improving EIA practice.
Matthew Elliott is a technical director at WYG. He is a Fellow of the Institute of Civil Engineers and a Chartered Environmentalist.
