Geoscience Reference
In-Depth Information
Table 5.6
Mitigation of aeolian hazards. (Summarized from Cooke et al. 1982.)
Method
Comments
Avoidance of problem areas
Removal of dunes
Vegetational
Best approach
Expensive, but successful for small dunes. Need to be maintained.
Protects the main area
Successful but expensive, and needs to be maintained. Careful plant
selection is required to survive the hydrological conditions
Needs to be maintained. In some instances mineral precipitation
associated with the evaporation of the water may enhance surface stability
Material greater than 2mm diameter used as an artificial pavement. Can
be costly to transport
Successful but unsightly
The chemical crust generated may be fragile and expensive
Sprayed as slurry with water fertilizer, grass seed and asphalt or emulsion.
Fragile but cheap
Can be living or artificial. Can be expensive
Set at an acute direction to the wind. Expensive and require maintenance
(removal of lee sand)
A series of fence increments, which extend the life of the barrier from
burial. Successful and relatively cheap
Minimizing the impact of housing on wind flow and sand accumulation
Natural recovery
stabilization
Artificial recovery
Surface
Water
stabilization
Lag
Oil
Chemical sprays
Wood cellulose fibres
Fences
Windbreaks
Diversion fences
Impounding fences
Architectural planning
such as pipelines, which are purposely exposed
for maintenance, can become inaccessible.
(surfaces more than 55° to the prevailing wind
direction) and fluting (surfaces less than 55°
to the prevailing wind direction) can occur on
buildings, and telegraph poles may suffer sand
blasting damage near their base. Glass becomes
frosted and paintwork may be damaged on
both buildings and vehicles. Air filters are also
affected. In addition, visibility can be impaired
by sand storms. Dust storms have been reported
to create many problems including the trans-
portation of pathogens, suffocation of cattle
and interference with reception on transmitting
and receiving devices.
5.6.1.2 Soil erosion
Loss of topsoil through deflation will inhibit
fertility, and can undermine structures through
scouring of footings. This can affect anything from
telegraph poles to pipelines, railway sleepers and
roads (Cooke et al. 1982). Typically once the
sand source has been depleted, and an armoured
surface has been reached, e.g. a gravel lag, or
where desert pavement predominates, then defla-
tion ceases to become a problem. It will only
remain a problem in areas where the sand supply
is continually renewed, e.g. in mobile dune fields
or along unpaved roads. The Arizona Depart-
ment of Transport (1975) reported an annual
loss of silt and clay by deflation at 5-50 kg per
vehicle per mile of unpaved track.
5.6.2 Water hazards
Despite the arid nature of drylands, water is
one of the main hazards in these regions.
From an engineering perspective ephemeral arid
streams provide a challenge. Peak sediment and
water yields are commonly associated with the
semi-arid environment, where drainage densities
are best developed (wetter areas have channel
development inhibited by plants and drier areas
have insufficient frequency of events to main-
tain channels). Some authors (e.g. Farquarson
et al. 1992) suggest strong similarities in flood
5.6.1.3 Sand abrasion
Transport of sand by aeolian processes leads
to the problems of abrasion. Typically, abrasion
is exacerbated over indurated surfaces such as
tarmac and concrete (Cooke et al. 1982). Pitting
