The fencing of watercourses is beneficial on many sites for a number of reasons:

• To facilitate planting of the riparian corridor and/or to increase

the vegetation cover

• To improve the river habitat through reduction of siltation

and agricultural diffuse pollution risk

• To improve the habitat and biodiversity value of the riverbank

• To assist agricultural management of the land

By thinking carefully about fencing on floodplain land, the risks canbe reduced and managed. The initial cost of floodplain specificationfencing is higher than that for ‘standard’ fencing work, due to theheavier specification materials and additional labour costs involved.

It is important to compare this against the reduced longer termrequirement and cost of repeated repair and replacement of fences.How do the costs stack up over the projected lifetime of a ‘normal’riparian fence?

Fencing of watercourses is often encouraged throughagri-environment provisions such as SRDP in Scotland, orEnvironmental Stewardship or Catchment Sensitive Farming Capital Grants in England. However, the capital costs supportthrough such schemes are paid at ‘standard item’ rates, which do not cover the increased costs of using a floodplain specificationfencing. This project aims to influence this issue going forward.

Further information on how floodplain specification fencing can be part of a larger project is available on the case studyentitled Sustainable Riparian Management.

Issue Date: November 2012

Contacts: Jennifer Hewitson. Northumberland National Park Authority | Tel: 01669 622 071Tracy Hall. Tweed Forum | Tel : 07824 197 016 www.cheviotfutures.co.uk | E-Mail: info@cheviotfutures.co.uk

Photos showing break and adjustment points in fence,they are designed to fail under excessive tension

Floodplain Fencing Specification

Approach case study

Fencing on a floodplain carries risk of damage, repair costs and total loss of fence lines as a result of flood events. These issues can be minimised throughenhanced specification.

The EuropeanAgricultural Fund forRural Development:Europe investing inrural areas.

The EuropeanAgricultural Fund forRural Development:Europe investing inrural areas.

Floodplain Fencing – Do’s and Don’ts

Do...

Choose the most suitable line, as far back from the actual river bank aspossible; parallel to river flow and make use of higher ridges of groundwherever possible.

Use good quality fencing materials (including appropriately treated timber), and suitably skilled persons to erect the fence.

Use plain wires, preferably high tensile for strength and durability.

Erect the fence in short discrete sections (20-75m lengths), with the ‘break points’ railed up.

Include plenty of re-tension points within the fence-line to facilitatere-tightening of wires within sections.

Include additional gripples on wires within sections to act as additional break points.

Position the break points within the fence-line at those points identified as being the most vulnerable to flood damage.

Check the fence thoroughly after each flood event to make any adjustments and repairs necessary.

Use a ‘running fit’ approach where staples are not driven all the way into the posts (not including strainers), to allow some ‘give’ in the wires tosupport weight of flood debris.

Keep the bottom wire high at known high risk sections – fill in below with rails or a small hinged watergate.

Do not...

Erect permanent fences unless necessary. Consider whether anelectric/temporary fence would be sufficient – this decision may depend on whether a mains electric connection would be feasible, and whetherthere is management capacity to check the connection regularly etc.

Fence immediately adjacent to the watercourse, or on unstable riverbanks.

Use sheep netting or similar – this increases the chances of debris becoming caught up in the fence during flood events, therefore increasing risk of damage and loss.

Fence across the line of flow unless totally unavoidable; where this is unavoidable, use a detachable water gate approach – chained at one end and tied at the other as a quick-release system.

Fence in one continuous line – although this is preferable from a fencingcontractor perspective, this means that if the fence becomes damaged by floods, the whole length, or a significant length, becomes damaged or torn out.

Over fence! Think about the lines that are needed and most efficientwithin a floodplain environment and remove redundant fences.

Wire or staple to natural features such as trees on the floodplain.

Cut post tops – this allows water to penetrate and reduces the lifespan of the posts.

.

• Locate fences at least 1.5m away from the bank top to allow

for riverbank re-growth

• Strainers – minimum specification of 2.3m length with a

18cm diameter

• Maximum spacing of 50m between strainers on a high flood

risk site; 50-100m in medium to low risk sites

• Posts – minimum specification of 1.7m length with a

9cm diameter

• Maximum spacing of 4-5m in high to medium flood risk

situations; 5-6m spacing on lower risk sites

• All posts and strainers should be driven in to full depth –

at least 1m for strainers and 80cm minimum for posts.

Floodplain Fencing Specification