Flood Risk Jargon Buster: 20 Terms Explained in Plain English

Understanding flood risk should never feel like decoding a technical manual. Yet for many homeowners, buyers and even developers, the language used in planning documents, Flood Risk Assessments and environmental reports can feel overwhelming. At Ashfield Solutions, we put a lot of focus on making flood risk clear and easy for the end user to understand. 

Whether someone is buying a home, investing in land or progressing a planning application, clarity matters. 

That is why we have created this plain‑English flood risk jargon buster, focused on the terms that appear most often in planning and property‑level flood risk work.

Climate Change Allowances  

• Climate change allowances are future uplift percentages applied to flood modelling to show how rising rainfall and river flows could affect a site. They help set finished floor levels, assess safe access and ensure mitigation remains effective throughout the lifetime of the development.

Design Flood  

• A design flood is the specific flood event used as the benchmark for assessing risk and designing mitigation. It usually includes climate change allowances and defence conditions. Using a consistent design flood ensures finished floor levels, access routes and resilience measures are appropriately set.

EA Model Data  

• EA model data includes hydraulic modelling outputs showing predicted flood depths, velocities, hazard ratings and extents. These datasets simulate river flows, rainfall events and climate change scenarios. We compare EA model data with on‑site ground levels to understand how flooding may affect development.

Exception Test  

• The Exception Test is applied when development is proposed in higher flood risk areas. It requires evidence that the project will be safe for its lifetime, will not increase risk elsewhere and will deliver wider sustainability benefits. It is used only when the Sequential Test cannot be met.

Finished Floor Levels  

• Finished Floor Levels (FFLs) are the height of internal floors relative to predicted flood levels. Raising FFLs above the design flood level is one of the most effective ways to keep properties safe. We regularly recommend minimum FFLs to ensure long‑term resilience.

Flood Performance Certificate  

• A Flood Performance Certificate is an emerging standard showing how resilient a property is to flooding. It helps homeowners, insurers and lenders understand risk and the benefits of resilience measures. Pilot projects are underway and interest is growing across the industry, something we explored in more detail in our recent blog Five Trends Emerging From Flood and Coast 2026. 

Flood Risk Assessment  

• A Flood Risk Assessment (FRA) is a technical report evaluating flood risk to a site and outlining the mitigation needed for planning approval. It considers multiple flood sources, climate change, safe access and finished floor levels, providing clear recommendations to ensure development remains safe and compliant.

Flood Warning and Evacuation Plan  

• A Flood Warning and Evacuation Plan sets out how occupants should respond to flood alerts and how they can safely leave the site. It includes trigger levels, routes, responsibilities and communication steps. It is often required for developments in higher flood risk areas.

Flood Zone  

• Flood Zones are the Environment Agency’s categories showing how likely land is to flood. They guide planning decisions, influence where development should be located and help identify whether a Flood Risk Assessment is required. They are one of the first checks carried out when assessing a site’s suitability.

Fluvial Flooding  

• Fluvial flooding happens when rivers overflow their banks during high flows or prolonged rainfall. It can affect large areas and is influenced by catchment size, land use and upstream conditions. Planning assessments consider predicted river levels, climate change allowances and how the shape and height of the land might influence where water goes. 

Groundwater Flooding  

• Groundwater flooding occurs when water rises up through the ground due to high water tables, often after prolonged rainfall. It can affect basements, low‑lying land and permeable geology. It is slower to appear and recede than other flood types and requires specialist assessment.

Hazard Rating  

• Hazard rating combines flood depth and speed to show how dangerous a flood would be for people. It is used in planning to assess whether occupants can safely move through or away from floodwater. Higher hazard ratings require stronger mitigation and careful site layout design.

Property Flood Resilience  

• Property Flood Resilience (PFR) refers to measures that help buildings resist, recover or adapt to flooding. This includes flood doors, raised electrics, waterproof materials and rapid recovery design. PFR reduces damage, speeds up recovery and provides practical resistance where traditional defences are not feasible.

Residual Risk  

• Residual risk is the remaining flood risk after defences or mitigation are in place. It includes defence breach, overtopping and extreme events beyond design standards. Planning assessments must show that development remains safe even if these unlikely but serious scenarios occur.

Safe Access and Egress  

• Safe access and egress ensures people can safely enter and leave a site during a flood. Planning authorities require evidence that occupants can reach a safe location without encountering dangerous water depths or speeds. It is essential for residential and mixed‑use developments.

Sequential Test  

• The Sequential Test ensures new development is directed to areas with the lowest flood risk. Local planning authorities use it to compare alternative sites and confirm that higher risk locations are only considered when safer options are unavailable. Recent NPPF 2026 changes have updated how this test is applied, which you can read more about in our recent blog.

Strategic Flood Risk Assessment  

• A Strategic Flood Risk Assessment (SFRA) is produced by local authorities to map flood risk across their area. It informs Local Plans, guides development locations and supports the Sequential and Exception Tests. SFRAs provide the strategic context for site specific flood risk work.

Surface Water Flooding  

• Surface water flooding occurs when intense rainfall overwhelms drains or cannot soak into the ground. It often affects roads, gardens and low‑lying areas and is increasingly common due to climate change. It is now one of the most frequent constraints raised during planning applications.

Sustainable Drainage Systems  

• Sustainable Drainage Systems (SuDs) manage rainfall by slowing, storing or filtering water. Examples include permeable paving, swales, ponds and rain gardens. SuDS reduce surface water flooding, improve water quality and support climate resilience in both new and existing developments.

Tidal Flooding  

• Tidal flooding is caused by the sea, storm surges or exceptionally high tides. It affects coastal communities and estuaries and can combine with river flooding to create more severe conditions. Planning work assesses predicted tide levels, defence performance and long‑term sea level rise.

Here at Ashfield Solutions, we focus on strengthening the connection between flood risk understanding and practical resilience on the ground. Our team works closely with insurers, local authorities and homeowners to ensure resilience measures are realistic, standards led and deliverable. 

We carry out detailed technical assessments to provide simple, actionable advice that supports clarity and, where possible, planning approval. You can explore our successful outcomes in our case studies.

If you need flood risk explained in plain English, speak to our friendly team of Flood Risk experts today.