Mitigation measures are more effective if they are designed as an integral part of the scheme. If consideration of mitigation measures is left until later in the scheme design, this can increase costs as early opportunities for avoidance are missed.
The 'Landscape Institute and Institute of Environmental Management and Assessment’s: Guidelines for Landscape and Visual Impact Assessment' includes principles on designing in mitigation to reduce impacts on landscape and visual amenity.
Mitigation may either be:
- Primary measures that intrinsically comprise the development design – i.e. buffer zones.
- Secondary measures designed to specifically address the remaining (residual) negative or adverse impacts – i.e. creating new landforms.
Mitigation measures can be reinforced by their adoption as conditions of approval, including as pre-commencement conditions (conditions that require compliance before development on site starts). Note: The long term protection of trees is best carried out by way of a TPO rather than by using a condition of a planning permission.
Limits of mitigation
Not all impacts can be mitigated and mitigation in itself can lead to problems with a development. Monitoring of a development is essential to overcome and identify unanticipated problems as they arise. Problems with mitigation include:
- Mitigation measures e.g. planting can take considerable time to become effective. Realistic growth rates must be applied. Semi-mature vegetation can be planted if screening needs to be effective immediately but must be carefully managed to avoid failure.
- Mitigation measures may only be effective on a seasonal basis e.g. planting with deciduous trees.
- Mitigation measures designed to overcome one adverse effect may give rise to other adverse effects e.g. planting can reduce openness or limit views to landmarks. This must be anticipated at the design stage.
- Mitigation measures can prove unfeasible to implement and the practicality of implementing these must be considered at the design stage through the identification of a suitable management plan. More information on this can be found in Stage 5 Design implementation and Management plans.
A standard hierarchy of mitigation measures is outlined below:
Avoidance is the preferred mitigation method and can be achieved through careful site selection, siting and innovative design
Reduction of impacts of development on the landscape can be achieved by setting the development into the ground and the implementation of sensitive design through the creation of new landforms
Remediation should only be used where either Avoidance or Reduction cannot be achieved. It can be achieved through cosmetic measures such as screening and re-planting of native species.
Compensation should only be considered as a last resort and only be used where impacts cannot be mitigated to an acceptable level.
A robust assessment of the nature, value and extent of the resource that would be lost is required at the outset of the planning process so that lost features can be replaced appropriately. In many cases, true compensation is unlikely to be possible, e.g. new woodland may replace mature woodland but is unlikely to compensate for the loss of established habitat.
Enhancement is always desirable and often used in conjunction with mitigation e.g. improved land management and the creation of new habitat areas.