Rethinking sustainable construction and development: Flood risk
Discussions about sustainability in the area of development and construction are often focused on the decarbonisation of buildings, particularly residential housing stock. There is often an increased attention on the methods and materials that can be used to improve the energy performance of existing buildings and on the need to reach net zero construction targets. These are important considerations, critical to the achievement of climate targets, considering the built environment is responsible for 40% of our national carbon footprint in the UK.
However, a truly sustainable built environment is about more than this. It also requires buildings to be fit for purpose, adaptable to future need, built to last, and affordable to live in or run. Any definition of sustainable construction should factor in the whole lifecycle of a building, its resistance to damage, including the likelihood that it would survive a fire or flood, and what the impact would be in the event of a total loss. Resilience and building safety are also important considerations. A mindset of repairing buildings in a more resilient way must also be adopted.
A true definition of sustainable construction must put the occupant first. It should carefully consider the needs of those people using the building, of vulnerable people who could face being rehomed in the event of a major flood, or of schoolchildren who could lose exam work or miss out on education if their school suffered a major fire. Zurich’s own definition of sustainability shows how we aim to take a broad, holistic view. We define sustainability as doing business today in a way that safeguards the future of our company and our society.
Flood Risk
Accurately gauging future flood risk is certainly challenging but organisations should consider if they are as prepared as they could be for what lies ahead.
A key area of focus for Zurich in relation to property risk over the last few years has been to increase understanding and awareness of the changing risk landscape in the housing and construction sectors. Flooding is one of the property risks causing greatest concern. Too often, homes are built using design and materials that offer minimal flood resilience. When planning approval is granted to developments in areas at risk of flood, planners are relying on the proposed flood mitigation measures actually being done, being done properly and in a way that mitigates against both current and future flood risk, which isn’t always the case.
Future flood modelling lacks consistency and clarity
Considering the bigger picture, and planning ahead, is made more challenging by the unpredictability of future flood risk and the lack of consistency in future flood modelling. The nature of flood risk is changing rapidly. We are seeing an increase in storms as a result of climate change, but there are also significant increases in incidents of surface water flooding, which is hard to model because it can be affected by factors such as drain maintenance and capacity, which are dependent on inspection and clearing schedules and regimes.
Published flood frequencies can also sometimes be misleading, meaning many occupants of properties do not understand their flood risk. For example, a 1 in 20 flood risk is not just a 5% chance of flooding. Return period descriptions like this are not an exact science and can give the impression that flood events are cyclical and therefore predictable, which they are not. Organisations cannot be expected to build in flood resilience measures for every development, but for higher risk developments, they should be considered carefully. You should really be looking 50-100 years ahead, because areas that are not currently prone to flooding could be in the future.
Building in resilience now helps to futureproof developments and could provide protection for residents and occupants for decades to come
Practical flood mitigation measures
On an individual building level, this could include taking simple measures now to prevent much more significant costs further down the line:
- Raising electrical sockets (and cables)
- Orientating plasterboard horizontally, instead of vertically, so that only the lower level boarding needs to be removed in a flood
- Using appropriate insulation materials (within lower level walls and beneath floors) that are resistant to the effects of water
- Greater use of moisture-resisting materials in the construction of fitted furniture, including kitchen units
- Ensuring ground floor construction, materials and finishes can resist the effects of water ingress. It is also important that organisations consider the potential impact of a flood on the entire development site, not just the properties themselves.
Zurich is aware of situations on developments where the properties were unaffected because they were raised up, but the access points were not, so people could not actually live in them because they could not get in or out.
Zurich believes that Sustainable Drainage Systems (SuDs) can play a pivotal role in ensuring that new properties are built in a manner which helps to manage surface water flood risk at the local level. Increased hard landscaping adds to the pressure on traditional drainage systems during periods of extreme rainfall. This is then compounded by the natural deterioration of drainage systems. Whilst we acknowledge that land shortages, and values, are likely to dictate which sites are chosen for development, together with both national and local planning policies, it is essential that drainage is properly taken into account within the wider catchment area, both upstream and downstream, and not just as part of the local development.
Creating a holistic view of sustainable development requires close collaboration between local communities and the anchor institutions that work alongside them. It is important to build a greater understanding about community needs and priorities, as well as resolving pragmatic issues such as how specific flood mitigation measures will be planned, prioritised and resourced.
Flood resilience: key takeaways
- Flood risk is changing rapidly. In many areas, previous resilience measures may no longer be sufficient. Building in a way that satisfies current flood modelling analysis, but which does not account for future flood risk, is unsustainable
- Resilience measures designed to protect developments in areas of increased flood risk must be demonstrably future-proofed
- Renovations or property repairs post flood must also be undertaken with the aim of making assets resilient to future weather events
- Incorporating defences now will save costs and losses in the future
