Road Networks

Roads cause disturbance of the natural environment, because soil is compacted, water run-off increased and soil erosion promoted. On a game ranch roads should therefore be positioned with care, with the effect and primary goal of each road being considered carefully. Three types of roads considered in most instances on a game ranch (Du Toit and Van Rooyen 2002):

  • Tourist roads aim to provide the tourist with the opportunity for viewing and experiencing the scenery and other natural resources on the game ranch. These roads should never include long straight stretches but should preferably twist through the bush along a contour line or an ecotone. An ecotone is a transition between two types of vegetation. The ideal road for game viewing will follow an ecotone, be situated in open veld types and be about 100 meter from the border of more dense areas. Tourist roads usually links waterholes, traverse as many veld types as possible and are also used for patrolling and capturing animals.
  • Firebreak roads should be wide enough – at least 8 m – to prevent accidental fires from crossing them. They should be planned and built in such a way that they separate the major veld types on the farm. This will enable the wildlife rancher to combine veld management with a burning program. A firebreak road can also serve as a tourist road and vice versa, as long as the road complies with the necessary specifications.
  • Hunting roads are often twisting, dual-track roads. They should be easily negotiable while disturbing the veld as little as possible. Hunting roads should enable the hunter or cropped team to deliver any hunted or captured animal to the skinning or holding facilities with the minimum delay. Hunting roads are usually used mainly during the hunting season.

Ecological effect

Depending on their construction and location, roads can have various ecological effects on a wildlife ranch. The following are some examples (Du Toit and Van Rooyen 2002):

  • construction work destroys plants, especially trees, and small animals
  • poorly planned roads may create erosion problems and lead to habitat deterioration
  • firebreaks are escape routes for most animals during veld fires
  • roads are used by animals as routes between watering points and grazing areas
  • animals such as impala and blue wildebeest sleep on roads during rainy or moonless nights, especially in areas where predators occur
  • culverts or storm water drains serve as burrows for warthogs, jackals and spotted hyena’s
  • baboons and monkey’s learn to beg along roadsides when fed by tourists
  • pioneer plants along roads attract hares and steenbok
  • snakes bask in the sun on roads when the day time temperature is low
  • ground-nesting birds often breed next to the roads
  • tarred road surfaces become smooth in time and animals running across such a road much slip and injure themselves
  • nocturnal animals are blinded by vehicle headlights at night and may be run over
  • quarries near roads provide water for animals out of season, which can lead to over utilization of certain areas
  • roads affect the movement of skittish animals such as eland. This can prevent such animals from reaching vital feeding and breeding areas
  • excessive water run-off creates vegetation thicket galleries next to the road, which can reduce the available grazing and be detrimental to tourism owing to limited visibility

Road construction

All unwanted objects such as rocks, tree stumps and roots in a strip of at least 5 m wide on either side of the planned road, and to a depth of 75 mm along the planned road area should be initially removed from a previously established terrain plan. The removal of all vegetation is essential because decomposing vegetation can cause the structure of the road surface to weaken. The number of layers of material used in the road varies from two to four and depends on the kind of road that is to be constructed. The top or crown layer is followed by a supporting layer, an upper selected soil layer and a lower selected soil layer, up to and including the road base. The amount of topsoil that has to be removed depends on the quality of the topsoil and on the road design. Topsoil can be stored in separate piles to prevent it from mixing with the base soil. This topsoil can later be reused for stabilizing the road shoulders, repairing disturbed areas and re-establishing the indigenous vegetation (Du Toit and Van Rooyen 2002). The management of road impacts is an important consideration for isolated reserves, particularly those situated in the urban fringe. For wildlife, the key issue is how impacts are felt across the landscape. Roads are unlike most other causes of fragmentation in that they continue to remove individuals through collisions with vehicles. There is speculation that roads may form habitat sinks for wildlife, drawing animals from surrounding areas, ultimately to their doom (Du Toit and Van Rooyen 2002).

Drainage of roads

Roads have a twofold drainage problem, the one occurs above the ground level and the other below it. Surface drainage involves the channeling of all rainwater from the road surface and the surrounding areas. Surface water should be prevented from reaching the underground drainage system by the following means (Du Toit and Van Rooyen 2002):

  • the design of a convex road surface
  • the placement of drainage canals parallel to the slope
  • by allowing storm water to pass underneath the road

Adapting the road design to the contours of the environment will allow for easier drainage. Underground drainage deals with water that has filtered into the road foundation and the surrounding material. This water can enter the road foundation through cracks or holes in the paving, through adjacent porous material, or from under the ground. Underground drainage is essential in (Du Toit and Van Rooyen 2002):

  • Areas with a high water table
  • Seepage areas under the road foundation
  • Active springs
  • Surface water that enters the road foundation from a high median or from side channels through a porous road surface
  • Areas with dolomite

Compaction and erosion

Compaction is the process by which the density of material is increased artificially as the component materials are pressed closer to one another by the process of kneading, pounding or shaking. Thoroughly rolling or stamping the soil and gravel that is to be used for filling ensures that the road will maintain its driving comfort, shape and strength throughout its normal lifespan. A road that is not compacted thoroughly will soon lose its shape and strength. The strength of the foundation layers is influenced by the following factors (Du Toit and Van Rooyen 2002):

  • Soil type
  • Compaction of the layer, the denser the layer the greater its strength
  • Moisture content of the layer, the wetter the layer the less strength it has

The latter two factors can be controlled by compaction, while the first one is controlled by the choice of suitable material. In practice, different types of mechanical rollers are used to increase compaction (Du Toit and Van Rooyen 2002). Protection of the slopes next to a road prevents damage to the road shoulders by wind and water erosion. Light soil or sand with a low moisture content are more prone to water erosion. Topsoil contains enough organic material and seeds of pioneer plants for the establishment and growth of plants along the road verges. The recommended thickness of the topsoil layer is 75 to 100 mm. Slopes with a gradient greater than 1:4 cause the topsoil to wash away. Obstructions should therefore be placed along the road shoulders to limit the runoff of rainwater. Plant material such as hay or straw can be used as a cover on slopes where topsoil is not available. This plant material encourages the germination of seeds, but is less effective in areas subject to wind erosion. The slopes next to a road can be packed with stones to limit wind and water erosion further (Du Toit and Van Rooyen 2002).

Recommendations for Highlands Wilderness

Water run-off is severe during rainy season, on the steep roads. It is advisable to construct enough drainage trenches or pipes to convey water. This will prevent water from running along the road surface and eroding all the lose gravel and dirt from the road forming gullies and washing out rocks. Firebreak roads on the mountain along the fence line should be cleared and maintained to prevent accidental fires to escape and cause damage to neighbouring properties. All the roads should be well maintained and regularly checked on erosion, potholes and downward slopes.

The major roads (Figure 26) on Highlands Wilderness are well maintained and are often graded. Most of the roads on grassland area (management unit 1) are straight and some motorist tends to travel these roads exceeding the speed limit on the ranch, putting animals at risk. It is advisable to construct humps horizontally on the roads, made of soil, every 100 m to control speeding vehicles. Most of the roads on the mountains are very steep and only suitable for 4 x 4 vehicles. Some of these roads would therefore, risky for game viewing with vehicle full of tourists since the road is rocky and could cause vehicle to slipper.