Asset Adaptation to Changing Flood Risk

• Strategies for managing flood risks including land management, infrastructure modifications, and behavioral changes.

• Wetland restoration and strategic urban planning are examples of successful flood management.

• Asset managers can use flood data and modeling to guide decisions on how to mitigate flood-related damages and improve asset resilience.

River flooding, surface flooding, and coastal flooding bring similar physical risks.

The options available to asset managers for adapting and retrofitting assets cover all forms of flooding, helping to reduce damage and losses from storm including tropical cyclones, storm surge, and landslide.

Three broad, overlapping categories of actions exist: land management, infrastructure changes, and behaviour changes including economic incentives and disincentives.

One clear way to stop flood damage and losses is to keep assets away from water by not building in floodplains, nor in areas into where floodplains might expand, or in areas where water pools during a storm.

Where data show that properties are already sitting in flood-prone areas, and perhaps have been flooded on previous occasions, divestment remains an option.

Avoiding assets in flooding locations is not always straightforward or cheap.

Moving away from one physical risk could expose an asset closer to another, such as subsidence or wildfire. Decommissioning properties and moving people elsewhere has huge costs, which can be modelled to develop cost-benefit analyses.

Despite the difficulties, many locations have succeeded in removing properties from floodplains.

After more than 80 people died across Ontario during Hurricane Hazel in 1954, Toronto decided not to rebuild houses along its main rivers. The city now boasts nature areas with bike/walking pathways snaking along the rivers through the city. Those ravines flood during storms, but with limited property damage nearby. Urban expansion, though, has increased runoff, so basement flooding where water pools is common.

Land management helps to reduce losses.

In locations in eastern England and the eastern US, coastal areas have been restored as wetlands such as salt marshes. These zones buffer between storm surge flooding and assets while providing runoff areas for rainfall. Care is needed not to lead to other problems, such as a breeding ground for biting insects.

Cultivation practices, too, make a difference.

Farms with furrows that channel runoff downhill can cause property damage with muddy runoff. On the other hand, agricultural practices that capture and store excess rainfall can enhance food production and reduce flood damage.

Creating other water storage places adapts assets to physical risks from floods by channelling water away from properties. Urban parks, playgrounds, and nature areas can be created in low-lying areas where water pools naturally. Then, they store water in heavy rainfall until it can drain, keeping assets dry.

Rather than moving assets or altering land use, infrastructure can be retrofitted or adapted directly.

Individual assets such as houses and offices could avoid placing valuables or irreplaceable items on the ground floor, in basements, or in cellars. An office block might use a ground floor for an open reception area while residential dwellings could avoid bungalows, so that people have upper storeys for their possessions and for evacuating to – assuming that the building does not collapse in a flood. Flood data and modelling for the future indicate whether or not a building might be inundated above the ground floor.

Specific elements within any building, from electrics to doors and from plumbing to paints, can be made water-resistant or easily replaceable on the ground floor and in basements. Models calculate the costs and benefits of these specific, focused interventions. Swift cleaning and disinfection after floodwater subsides is key to re-occupation without adverse health impacts or continuing losses.

The placement and orientation of assets with respect to possible floods must be considered.

With flood-resistant outer walls, a building can be sited to direct water away rather than letting it infiltrate inside. Assets must be designed, built, and maintained to avoid collapse or undermining as floodwater and landslides flow around it. Wider planning can stop re-directed floodwater and mud from damaging other properties, instead running into waterways, bodies of water, or green spaces.

Wider planning could involve infrastructure changes through building flood defences. London, Rotterdam, Singapore, and Venice among other cities use massive barriers to tackle coastal flooding and river flooding. Long swathes of Belgium’s and the Netherlands’ North Sea coasts use shifting beaches and fixed dunes to avoid storm surge flooding assets inland. Roads, car parks, and pavements can be constructed from porous materials so that rainwater soaks into the ground underneath, rather than running straight to sewers or into properties.

Many anecdotes are told of people receiving a flood warning and moving their old furniture into the basement under the assumption that their insurance will buy them new-for-old.

People do change their behaviour according to the information that they receive.

Asset managers and insurance companies can support behaviour change in a fair and equitable manner, which helps themselves and their clients in saving money, time, and stress.

Refusing to insure can be tricky when a customer has lived in a place for a long time. A newly uninsurable property can be unsellable, trapping people in a flood-vulnerable location with no way out.

Conversely, when new assets are proposed in flood-prone areas, asset managers and insurers can take a proactive approach. They can clearly communicate that they will not provide any products or services to clients in these areas unless the assets are made flood-resistant. Additionally, they can focus on developing new products that offer affordable insurance without increasing the risk to existing assets.

One significant behaviour change for asset owners and managers to investigate through models is to accept that floods happen, rather than trying to stay entirely away from water.

Besides making changes to infrastructure to lessen damage, another option is to simply be prepared to pay for flood damage and disruption when it happens, especially if this is cheaper than making other changes. Being adaptable oneself means having the psychological fortitude, finances, and alternative accommodation all available to deal with changing flood risk.

Numerous options exist and can work in tandem, supporting decision-making by asset managers to adapt to and retrofit for changing flood risk.