Options Development and Design

Too often, property owners are tempted to skip straight to construction, for example, asking a builder to install a flood wall. On the surface, this may seem like a sensible solution, but without proper design, walls can fail, drains can be overlooked, and in some cases the risk to neighbouring properties can actually increase.

Stage 3 is about preventing those issues. It ensures the options are based on necessary site information, plus being modelled, calculated or designed correctly so that the chosen measures deliver the right outcome, without creating new problems.

Depending on the property and type of risk, Stage 3 may include:

• CCTV Drainage Surveys
• Drainage authority searches (CON29DW)
• Floodwall designs
• Drainage design
• Site meeting with a Construction Project Consultant to assess buildability
• Floodplain Impact Calculations
• Soil analysis and foundation design
• Topographical surveys
• Structural calculations
• Environmental permits and planning permissions
• Design Risk Assessments (product choice, durability, long-term use)
• Hydraulic modelling, such as Micro Drainage, to test new systems
• Waterproofing options, repointing, tanking, and improving flood barrier performance through good masonry preparation.

In some cases, this may simply involve selecting the most appropriate barrier, non-return valve, or flood door. In others, it may require more advanced solutions, such as a new surface water drainage system or a flood wall with any necessary compensatory storage.

At a property in Nottinghamshire, our Flood Survey highlighted that traditional resistance measures alone would not provide the client’s desired outcome. By progressing to Stage 3, we analysed the existing drainage network, carried out detailed design work, including MicroDrainage modelling, and designed a new drainage system could protect the property up to a 1 in 100 year + climate change storm event.

This level of resilience would never have been achieved without Stage 3: Options Development & Design.
Read the Case Study here: PFR Survey and Drainage Design for Nottinghamshire Property

One area we are often asked to support with is flood walls. Interest in these has increased in recent years, particularly following high-profile examples such as Nick Lupton’s home on the River Severn, where a purpose-designed wall successfully held back flood water.

However, building a flood wall is not simply a case of constructing a barrier. Before a wall can be designed properly the wider site needs to be understood. Drainage arrangements, ground conditions, the nature of the flood risk, and how flood water interacts with the site all need to be considered. In many cases the displacement of flood water also needs to be assessed and an Environmental Permit may be required.

Structural engineering design is then required for both the wall and its foundation. Without this work a flood wall can create a false sense of security. In some situations it can even make flooding worse elsewhere.

This stage involves additional investigation and design work, but it ensures the solution is technically sound and avoids unintended consequences such as increasing flood displacement.

Building a Wall as a Flood Defence: Permits and Permissions