Vahryous Thoughts
As we head into the wetter months of the year, it is perhaps timely to consider the management of water on the routes that we use for four-wheeling. We know that our activities are being watched in relation to the movement of mud and silt by many agencies, such as local authorities and Waka Kotahi NZ Transport Agency.
There’s no question that the tyres of a 4x4 will disturb some soil in most circumstances. Once those soil particles are loosened, they are easily transported by moving water and the faster the water is moving, the more soil particles it will shift.
Standing water on a soil/clay based track will soften the ground and can create its own problems. On a ‘benched’ track cut along a hillside, the presence of standing water can cause that water to saturate the subsoils to the extent that they are weakened enough to simply slump away in the form of a ‘slip’. Such slips are costly and complex to repair and may simply just result in a complete closure and the loss of that route to vehicles.
Potholes can quickly form on almost any route when the ground is damp and again when more water is introduced, the outcome can be dramatic, with wheels being spun on wet soils and silt created instantly.
Risk management
Fortunately, there are ways to minimise the creation of silt in waterways which is something to be avoided, given the penalties imposed on four-wheeling by the Environment Court in Wellington back in 2019. Probably the most obvious is to not drive vehicles across soils when it is wet. That is not always practical, so we need to consider managing the risks.
One way is to reduce the amount of water and its speed across the ground. Strategically placed diversions can move water off a track, and it is important to avoid allowing water flows getting much speed, as again it will scour soil particles quickly. Using raised ‘bunds’ that are easy to drive over but are high enough divert water into drains will often work well.
Another technique is the rubber ‘water-bar’ where a strip of rubber conveyer belting is sandwiched between timber leaving a flexible ‘tongue’. The timber section is buried in the track at an angle so the exposed tongue then can ‘turn’ the water flows off the track. The rubber belting bends under the weight of even a mountain bike wheel.
Water holes and mud are often a favourite of some four wheelers, even though the consequences of water and a muddy grinding paste in moving machinery parts is usually expensive. Over many years of experimenting with ways to ‘harden’ wet areas to minimise the effects of tyres, one technique has often had good success.
This is the use of natural fibre sacks of Hessian/Jute containing rocks or gravel. The sacks make it easy to transport the rock and when placed in a wet area the silt particles tend to bind with the sack fibres and fill the gaps. Sourcing ‘hard fill’ material such as gravel can sometimes be resolved by locating those roadside gravel dumps where road repair sweepings are often left. Don’t raid those piles of clean road metal. River stones work well too. Because the sacks are manageable, we’ve often encouraged people on a trip to load one or two into their vehicle and then offload them when they identify a problem spot.
Bean bags are best!
The bags eventually rot away leaving little evidence of their presence. It used to be that we could buy ‘potato sacks’ at less than a dollar each, but those days have gone. However, the passion for coffee in New Zealand means hundreds of clean Hessian/Jute coffee bean sacks are discarded by various coffee roasters. Those sacks are bigger than needed but can just be filled accordingly to a manageable weight and then folded over… again the sack texture binds with the soil to help harden it. Just ask your local coffee roast company if they can provide you some sacks. Those woven plastic sacks used in agriculture etc. are not suitable, as the silt just washes off and as they decompose in sunlight, the plastic fibres then wash away, creating their own problems.
The reference earlier to Waka Kotahi NZ Transport Agency recognises that they do not like mud on their highways. The fines imposed for dropping mud off a vehicle could ruin an otherwise good day and the random lumps of mud are no fun to other road users, especially motorcyclists.
As a recreation we are going to need to be more aware of the sensitivities around how our activities affect the wider community. We are to a large extent being impacted by the growth in popularity of four-wheeling, which has happened without any equivalent increase in suitable venues. It is hard to visualise the current government and its associates being sympathetic, so it will be up to ourselves to present a better image and band together to identify that we are not a rabble, but good citizens who deserve more than we’ve been getting as a recreation.