FAQ: Flood Mitigation

12th May 2019

What do engineers, contractors and planners need to consider when working on a project that involves flood mitigation?

Why might contractors or engineers be increasingly concerned about flooding?

Minimising flood risk is one of the most urgent tasks facing today’s contractors and drainage engineers. Global climate is changing, rainfalls are increasing and the impacts are becoming more severe. Flooding is a global issue and both partners are under considerable pressure to provide effective, sustainable and cost-efficient solutions.

Regulation is becoming more stringent across regions, so any solutions put in place to mitigate the effects of flooding must consider these requirements, as well as environmental benefits and impacts. This isn’t the only requirement on contractors and engineers, however. They must recommend or design a solution that is within budget, delivered on time and sustainable.

Most importantly? They must deliver a solution that can mitigate today’s flooding and flooding possibilities of the future.

How can I ensure that my design stays within budget and is delivered on time?

Design engineers should start discussions with manufacturers of flood mitigation systems at the earliest stages of a project. They must scope out budget, capabilities and requirements as soon as possible so the compatibility of a potential solution is fully understood.

While preliminary talks are essential, it’s crucial that both engineers and contractors consider the whole-life cost of the project. Mitigating flooding doesn’t just stop after the solution is implemented. Costs of operation, maintenance and repairs should all be considered within the budget.

What can inform the success of a design and specification?

There are several critical factors to keep in mind when planning and specifying a solution for any flood mitigation scheme. The end goal, of course, is to mitigate the impacts of flooding, minimising likely risks and maximising returns. Whatever the solution, however complex, it will be expected to last for years, particularly within the decades region.

The design and specification stage needs to be driven by hard data. This data should be collected around the following areas:

  • The maximum capacity of the watercourse
  • Predicted storm flows for the required storm event
  • Ground and topographic data
  • Client and legal requirements for discharge quantity and quality

Acquiring this data will enable you to determine sizing, the required nature of the flood control solution and costs.

Why is sustainability crucial for flood mitigation projects, and how can it be achieved?

Flood mitigation projects need to be sustainable in terms of the environment, in terms of cost and in terms of longevity. In fact, sustainability has become the overriding objective in any project. This sustainability all comes down to how effectively the systems operate throughout its anticipated lifetime.

Whole-life costs, and successful optimisation of related ecosystem services, play a major role in determining the success or failure of a scheme. Other areas that will contribute to the sustainability of a project include ease of use and access.

Regulation is a serious requirement in flood mitigation, where can I find advice?

There are strict regulations in place around the world; we will focus on the UK, USA and Australia to provide representative examples. Each region has its own regulatory body and its own requirements; contractors and engineers should be aware of these requirements as they will shape any specifications made. They also have a responsibility to communicate these to the end user or site owner.


The regulatory framework for floodwater management in England and Wales is mainly set out in the Flood and Water Management Act 2010, the Flood Risk Regulations 2009, the Water Resources Act 1991, the Environment Act 1995 and the Land Drainage Act 1991.

In Scotland the relevant legislation is the Flood Risk Management Act (Scotland) 2009 and the Water Environment and Water Services (Scotland) Act 2003.

The environmental regulators (Environment Agency, Scottish Environment Protection Agency, Natural Resources Wales and Northern Ireland Environment Agency) have the strategic overview of all sources of flooding and will be supported by local authorities, water and sewerage companies, highways authorities and internal drainage boards among others.


In the USA, responsibility for flood risk management is shared between multiple Federal, state and local government agencies. At a Federal level, the lead flood control agency is the US Army Corps of Engineers (USACE) with the Federal Emergency Management Agency (FEMA) taking the main role in emergency situations.


The Australian Institute for Disaster Resilience publishes a guide to best practice in flood risk management that provides useful information on roles and responsibilities, while Australia’s National Climate Change Adaptation Research Facility’s Living with Floods report calls for full cost and benefit analysis for flood plans and recovery programs.

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