This document sets out the policy of The Inland Waterways Association (IWA) regarding the management of vegetation by navigation authorities on the inland waterways of England and Wales.
Vegetation, when properly managed, is an important and attractive feature of the waterway environment. It also fulfils a key role in the stabilisation of riverbanks, consolidating embankments and water table control. The uncontrolled establishment and growth of vegetation alongside a navigation can, however, cause personal injury, damage to craft, reduce amenity, and adversely affect the water environment.
IWA considers improved management of vegetation is essential in order to optimise benefits to all waterways users as well as to enhance good environmental practice. IWA considers that all navigation authorities should have policies in place in place that give proper priority and attention to the management of vegetation along the waterways for which they are responsible, and will encourage navigation authorities to comply with such policies.
The principal aims of IWA with regard to vegetation management on the waterways are:
IWA is cognisant of the constraints placed on navigation authorities by environmental controls and legislation regarding the time of year as well as the techniques to be employed to minimise disturbance to wildlife control of vegetation. However, vegetation management on a navigation should not result in any deterioration due to compliance and, where possible, should contribute to achievement of environmental targets. IWA would like to see a uniform approach adopted by all navigation authorities for the management of vegetation, especially when the control has been out-sourced.
Trees along most broad river navigations have a positive rather than negative impact on the navigation and are often the responsibility of the landowner. Therefore IWA recommends that action be taken only when a problem is identified.
It is considered that periodic audits (at least annually) should be carried out of vegetation along the various navigations to identify where work is required to implement a plan to achieve and maintain the satisfactory standards which are shown below:
This should be achieved by:
It is appreciated that aquatic vegetation provides valuable structural habitat for fish, invertebrate animals and other plants but excessive growth of emergent species can restrict the width of the navigation channel. Submerged and floating species can foul boat propellers if present in the main navigation channel. Excessive growth of filamentous algae such as blanket weed (Cladophora spp.) or invasive species such as floating pennywort (Hydrocotyle ranunculoides) can cause problems for navigation as well as oxygen depletion in the water.
Uncontrolled in-channel vegetation can adversely affect navigation, diversity, and flood risk management and IWA will encourage and support navigation authorities in controlling and removing these plants.
Invasive Non-Native Species
Where found invasive non-native species should, if practicable, be removed. If the growth is extensive then action should be taken to reduce its presence by restricting further growth pending action for eventual removal of the plant. IWA will encourage and support navigation authorities in controlling and removing these plants.
This policy should be read in conjunction with the IWA Towpaths Policy and the policy statement on Standards for Construction, Restoration and Maintenance of Inland waterways.