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3.3 Ecological Guidelines
GOAL
That structures do not cause undesirable changes to
terrestrial and marine ecosystems
3.3.1
Introduction
Whilst
the Guidelines are intended to primarily address site planning and visual
landscape matters, ecological impacts need to be considered.
The Ecological
Guidelines are designed, therefore, to deal with the impact of development
on coastal ecosystems. The assessment of ecological impact is particularly
important in coastal areas where the stability of natural systems is
often fragile and the restoration of disturbed systems difficult.
Generally, the
elements and processes within ecosystems are inter-related and the disturbance
of one process or the partial destruction of one element may affect
the whole system.
The major impacts
of development on coastal areas are:
(a) Soil erosion
resulting from the removal of vegetation and changes to drainage patterns.
The erosion of unstable exposed sand dunes by wind, after removal
of vegetation, is a particular problem.
(b) Loss of
animal habitat resulting from the removal of vegetation, farming,
urban activity, draining and filling of wetlands and estuaries and
water pollution.
(c) Depletion
of beach systems and siltation caused by interruption of marine sediment
supplies and the movement of marine sediment by walls, groynes and
breakwaters and changes in natural drainage patterns.
(d) Deterioration
of the quality of the water caused by the discharge of sewage fertilisers
and toxic chemicals and changes to water circulation patterns.
These impacts are
primarily due to alterations to land drainage patterns, vegetation,
soils and direct changes to sea water quality and circulation. It is
also important to anticipate the impacts of change, even on remote marine
ecosystems.
The geomorphology
of the area is an important consideration in understanding the suitability
of sites.
In all cases every
effort should be made to preserve natural systems. This is desirable
not only to maintain the quality of natural ecosystems, but also to
avoid expensive protection and reconstruction works such as those associated
with dune erosion, beach erosion and siltation. Changes to estuaries
and wetland systems by reclamation or drainage works can have significant
impacts on fish breeding in these areas, which is of great consequence
for the fishing industry.
In some circumstances,
it is necessary that structures do interfere with natural coastal systems,
either where natural processes threaten existing developments, or where
it is necessary to control the natural system and, in some instances,
completely change it in areas of intensive development, such as ports.
Where erosion threatens major roads or urban areas, it may be necessary
to erect protective structures such as sea walls or groynes. In these
instances, however, it is important that other alternatives, which may
be less disruptive of natural systems in the long term, are considered.
For example, sand pumping or moving threatened developments inland may
obviate the need for construction of protective walls.
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3.3.2
Land Drainage
(a) Siting, design
and construction of any structure should result in minimal change to
the natural drainage patterns of the area.
- Retain drainage ways and their associated vegetation in their natural
state. In particular, water flow in streams, creeks and natural drainage
swales should not be altered by changing the channel shape and surface
(e.g. by constructing a concrete culvert) or by damming.
- In developed areas, approved stormwater drainage disposal systems
may be required to improve natural drainage.
- The drainage pattern of an area is affected by changes to the stormwater
run-off volume and rate. To reduce run-off, impervious surfaces should
be limited to the minimum possible and the development planned to
utilise permeable surfaces wherever feasible. Where possible, run-off
should be detained, e.g. in catch basins, to achieve a flow rate simulating
the predevelopment state.
- Confine construction to the minimum area possible and provide temporary
water catchment until the stormwater drainage system is installed.
- Where connection to the local stormwater is not possible, run-off
should be diverted and dispersed (e.g. by using soakage pits).
- Do not fill or build over seasonally wet areas.
(b) Siting, design
and construction of any structure should result in minimal deterioration
in the quality of run-off water.
- To minimise the deterioration of run-off water quality: > control
soil erosion both during construction and in the finished development;
> minimise contamination (from manure and fertilisers) of drainage-ways
in rural areas; > eliminate discharge of toxic wastes into drainage-ways.
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3.3.3
Vegetation
(a)
Natural vegetation should be disturbed as little as possible.
- Structures should be sited and designed to have minimal impact on
existing vegetation.
- Where possible, disturbance to natural vegetation should be reduced
by grouping structures and providing common access points.
- Vegetation should be protected during construction to minimise unnecessary
loss.
(b) Natural
regeneration should be encouraged and extensive planting of indigenous
species should occur around development in urban, suburban and rural
areas.
- Where replanting of indigenous species is undertaken, the natural
hierarchy of trees, shrubs and ground covers should be restored.
- Topsoil should be stockpiled and re-used on-site to facilitate regeneration.
Re-use should take place as soon as possible, to ensure germination
of the maximum possible number of seeds.
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