Guidance on selecting mitigation measures


The purpose of this section of the website is to provide information to support the selection of appropriate mitigation measures for different flood risk management and land drainage activities. Different flood risk management and land drainage activities change the physical form and functioning of a water body (hydromorphology) quality elements in different ways. By linking each type of flood risk management activity to the potential hydromorphological changes, appropriate mitigation can be identified. For example, a weir can affect the movement of sediment through a river system, which in turn can impact on aquatic flora and fauna.

The information contained in these pages is intended to be high-level, generic guidance only.  In all instances, the site/scheme specific conditions should be considered and assessed. Advice from an experienced geomorphologist and ecologist may be required to ascertain which mitigation is appropriate for a specific site.  When applying measures it is important to remember that functioning systems are dynamic and taking an action to mitigate may also cause changes elsewhere in the system which need to be carefully assessed.  Click here for more information on geomorphological assessment and key guiding principles.

Step by step guidance

The above diagram illustrates the process used to help identify applicable mitigation measures for FCRM and land drainage activities. The process is not necessarily linear as in most cases more than one engineering activity will have been undertaken or proposed so some iteration may be needed but the process will help in defining most commonly appropriate measures.

Select a flood risk management or land drainage category
The first step of the process is to select a flood risk management or land drainage category from the list below. Separate lists are provided for the river and transitional/costal environments. Click on each category to progress to the following stage. For example, if you are looking for mitigation measures which could be appropriate for a weir, this would fall under the ‘on-line structures’ category.

Select a flood risk management or land drainage activity
Once a category has been selected, you will be presented with a table containing a list of more specific activities. A definition of the function of each activity is provided on this page. You can return to the main page at any time, by clicking the ‘back’ button on your browser or clicking the link 'Back to Engineering Types' at the bottom of each page.

Identify the potential hydromorphological change(s) associated to each activity
For each activity, a list of potential hydromorphological changes is provided. The list of the hydromorphological changes is presented in alphabetical order (i.e. the order from top to bottom does not correspond to importance of impact). Not all hydromorphogical changes may be expected from a particular scheme or project and the list is provided for guidance only. In addition, it is important to recognise that the cause of the change may be complex and may need assessment by a geomorphologist.

Applicable mitigation measures mitigation measure(s) based on hydromorphological change(s)
Having clicked on a hydromorphohical change, a new page opens. A definition is provided for each hydromorphological change. An overview of the causes and impacts of each hydromorphological change is also provided to help aid the selection of the appropriate mitigation measures. Finally a list of possible mitigation measures is provided at the bottom of the page. A short summary of each measure describes how the measure can help mitigate the hydromorphological change in question. In many instances, more than one mitigation measure may be appropriate for a specific scheme. For further information on each measure, click on the measures page.


Flood risk management and land drainage categories

Guidance on selecting mitigation measures