SC060062 - The Ecological Impacts of Flooding - Developing a Methodology

Theme:Modelling and Risk
Project status:Completed
Start date:01/07/2006
End date:01/10/2014
  • land quality,
  • Flood Defence,
  • conservation and ecology,
  • environmental management


When developing plans to manage flood risk, economic, social and environmental impacts are considered. There are many tools to estimate economic benefits of our work however there is no standard approach for evaluating the impacts on the natural environment. 

In 2006, Defra and the Environment Agency undertook a project to help assess the ecological impacts of flooding. This project undertook a desk-based review to understand how sensitive certain habitats are to flooding, and developed a tool to enable staff to understand the impacts of a range of flood regimes on ecology.

Floods can be both beneficial and harmful. They can create, maintain and even destroy habitats. They can bring both nutrients and pollution to the floodplain. Floods affect different species in different ways, and for many species, the impact is not direct. For some species it depends on what time of year flooding occurs.

This project brings together information from existing science to provide a framework for decision making. A methodology and tools were developed and provide an assessment of the ecological impacts of flooding, which could be applied at any scale.

The original tool, a series of spreadsheets, can be used to determine the ecological impacts of different, current and future, coastal and fluvial, flooding scenarios. For a range of flood scenarios, the tool enables you to look at the positive and negative impacts on the habitats listed below:

River - floodplain ecosystem impact
BAP priority habitats
In-stream ecology (, macrophytes, invertebrates)
Wetlands (for birds)
Coastal vegetated shingle
Sand dunes
Saline lagoons

For river systems the impacts of different flood scenarios and the seasonality of flooding can be assessed. For the coast, present day sea levels were compared to projected sea level rise estimates to assess the coastal flood impact at mean high/low water spring and neap tides.

This work will help the Environment Agency fulfil duties under the Habitats Directive, the Birds Directive and the Water Framework Directive. 

In 2014, we reviewed and assessed the usability of the tools developed and made recommendations for their future development.

It was recommended that:

• the methodology is improved to take account of new legislation and data sources
• tools are made more user-friendly by creating two-layers of interactivity:
- one for users with a technical working knowledge of GIS software 
- a set of GeoPDFs for users interested in the specific outputs

The outputs of the original project and 2014 review will be considered further when implementing future research and building future tools. For example, some of the recommendations could be used to support ecological impact assessments through further development of the Modelling and Decision Support Framework (MDSF2) and communities at risk project. Also to inform the development of Working with Natural Processes opportunity maps.

We are keen to hear more from others in the scientific community – the reports are available on request from: