The Importance of Fences in Floodplains

Building fences and building fences in floodplains has divided communities on many levels. Used to define what is “ours”, to prevent access to river systems, to prevent stock from entering other properties or even as a statement piece in a garden. As a result, we view our communities as individual pockets of land, a far cry from our natural heritage where the land was defined by valleys and gullies, with the rivers, streams and creeks dominating the landscape.

This is until it rains, and rains, and rains.

The flooding occurring in Victoria during 2010, 2011 and 2012 caused widespread damage, and in many cases the loss of fencing. The loss of fencing altered the course of what was previously assumed to be an inconsequential part of floodplain management. Specific types, designs, constructions and locations of fences in active floodplains were discussed in floodplain management meetings throughout the state. As such, guidelines were developed by the Department of Land, Water and Planning (DELWP) in collaboration with Catchment Management Authority’s (CMAs) and many other stakeholders to “help choose the best techniques for siting, designing and constructing fences in flood-prone areas”[1].

It is an offence to direct or outlet stormwater onto a neighbour’s property as it may result in damage. In the case of building a new fence in a floodplain, government agencies require flood modelling in order to prove there are no impacts on neighbouring properties or other public or private assets.

If you are planning on building a fence on your property or working for a client located within a floodplain, then read below to understand more about fencing requirements and flood prevention.

Building Fences in Floodplain Checks

There are two checks that will offer you the best support when trying to build a fence.

Check your local zones and overlays

If you are in a Land Subject to Inundation Overlay (LSIO) or Floodway Zone (FZ) you will have to contact the government organisation in charge of your region, generally Councils with specific contributions from CMAs or Melbourne Water in Victoria, Aus.

If you are rejoicing that you are not subject to either condition, just hold your horses. Many rural townships and areas do not have the appropriate modelling available and subsequently have no planning scheme for these specific zones. Therefore, you must contact the Councils and CMA to confirm.

Check if you are in a floodplain

There are two simple checks you can conduct.

1. The first is establish whether you are near a waterway, however this is not always a reliable method. If you are in a valley or know of recent flooding in the area, you could possibly be in a floodplain. Melbourne is built on swampland and much of the suburbs are subject to some sort of flooding. In rural areas floodplains are extensive from the Campaspe River, Loddon River, Murray River, Goulburn River, Glenelg River, Broken River, Yarra River, Avoca River and the Barwon River.

2. The second and easiest check is to call your local CMA and speak to the Flood Management Team.

You can request a letter stating the location of the flooding and the heights of the 100-year (1% AEP) event. Otherwise, call the Infrastructure Manager at your Local Council and discuss your query with them. Honestly, they will likely suggest contacting the CMA.

The contact details of the CMAs are below.

• North Central CMA – (03) 5448 7124

• Corangamite CMA – (03) 5232 9100

• Glenelg Hopkins CMA – (03) 5571 2526

• Wimmera CMA – (03) 5382 1544

• North East CMA – (02) 6043 7600

• West Gippsland CMA – 1300 094 262

• East Gippsland CMA – (03) 5152 0600

• Goulburn Broken CMA – (03) 5822 7700

• Mallee CMA – (03) 5051 4377

• Melbourne Water – 131 722

Guidelines for Building Fences

The guidelines for riparian fencing in flood‐prone areas, as mentioned in the introduction; click below:

Fact-sheet for Riparian Fencing in Flood-prone Areas

Guidelines for riparian fencing in flood‐prone areas

The technical assessment is generally down to the company installing the fences. However, as many fences in rural Victoria are largely completed by property owners a read through of the above-mentioned guidelines is a must. Prior to building any fencing in a floodplain, the owner must contact the CMA and provide drawings of the proposed fencing.

The North Central, North East and Glenelg Hopkins CMAs provide examples on potential fencing options.

FloodSafe Victoria provides ideas on structures and the general practise of understanding flooding.

Floodplain Fence Ideas

A few things to contemplate before heading to the CMA with your fencing plan:

• Fence further from waterways, in some cases at least 100 metres (where applicable), allowing for vegetation to grow along the banks. This preserves the riparian zone and will benefit landowners, discussed in more detail here

• Fence parallel to the likely floodpaths; this generally decreases damages incurred during a flood event

• Simple 1 to 2 wire fencing limits the impact of debris collecting

• Fence above the proposed flood level

• In urban areas leave a significant gap of 100-200 mm under the fencing

• Create a hinge system or cat flap at the bottom of the fence

• The taller the fence, the less steadfast it will be during a flood event

For further ideas on fencing solutions look here.

Innovation

A few companies are now selling fence posts and fencing alternatives to combat the issues caused by flooding. The ability for the fence to float may provide a viable alternative in the future, but contact Council and CMAs to confirm as many of these innovations have been unsuccessful in the past and may cost you a lot of money for the same outcome.

References

[1] DELWP Fencing Guidelines 2015