Using DCE evidence in environmental impact assessment

Using DCE evidence in environmental impact assessment

Environmental impact assessment increasingly requires quantified evidence of the value of environmental goods affected by proposed developments. DCEs provide that evidence.

This article explains how to use DCE evidence in environmental impact assessments, what planners and regulators need from the evidence, and how to present WTP estimates in a format that supports planning decisions.

Knowledge Base -> Putting It All Together -> Environment

Why EIA needs DCE evidence

Environmental impact assessment (EIA) for major infrastructure projects - roads, power stations, housing developments, industrial facilities - must evaluate impacts on environmental goods: landscape, biodiversity, water quality, recreational amenity, air quality. Historically, these impacts were described qualitatively or assessed against regulatory thresholds.

Planning authorities and regulators increasingly require quantified economic evidence of environmental impacts, particularly for developments that trigger strategic environmental assessment (SEA) or for appeals where the planning balance is contested. DCE studies provide the monetary estimates of environmental value that can be entered into the planning balance alongside development benefits.

How DCE evidence is used in EIA and planning

WTP estimates from DCE studies can be used in several ways in EIA: as direct inputs to environmental cost-benefit analysis alongside infrastructure benefits; as evidence of the significance of environmental impacts when expressed relative to household income; and as evidence of the distributional impacts of development (whose amenity is affected and by how much).

For major infrastructure planning in the UK, environmental WTP evidence is expected under the National Planning Policy Framework (NPPF) and supporting guidance from the Department for Transport and DEFRA. For developments subject to Habitats Regulations Assessment, DCE evidence can support the 'imperative reasons of overriding public interest' test.

SurveyEngine has supported DCE studies for EIA purposes across highway schemes, renewable energy developments, flood defence programmes, and urban regeneration projects.


Preparing DCE evidence for EIA

Step 1: Identify the affected environmental goods. Working with the EIA team, identify the specific environmental attributes that will be impacted by the proposed development. These become the attributes of your DCE.

Step 2: Define the affected population. Who lives within the impact zone? Who visits the affected area for recreation? Who has existence values for the affected habitat? The affected population determines your sampling frame.

Step 3: Quantify the impact levels for the DCE. The levels in your DCE should reflect the range of environmental outcomes possible under different development scenarios - from worst case (no mitigation) to best case (maximum mitigation). The developer or EIA consultant should provide the modelled impact scenarios.

Step 4: Estimate WTP with appropriate scope and scale. Ensure your WTP estimates cover the specific scope of impact - not just the affected site in general but the specific attributes and the specific level of impact. Aggregate to the affected population using census-derived household counts.

Step 5: Present evidence in planning-authority-friendly format. Planning authorities are not DCE specialists. Present your WTP evidence as: annual WTP per household for the specific impact; total annual impact on affected population; and comparison against the monetary value of the development benefits.

Worked example - renewable energy development

A DCE is conducted to value the impact of a wind farm development on landscape amenity, recreational access, and bird populations in a rural area. WTP estimates for the three impacts are: landscape change (negative visual impact from 15 turbines) = -£42/household/year; recreational access (2km of footpath diverted) = -£8/household/year; bird population impact (no significant effect on red kite population) = £0.

Total annual impact: -£50/household/year × 12,400 affected households = -£620,000/year. Present value over 25-year operating life at 3.5% discount rate = -£10.4 million. The developer's economic benefit (energy output value, local employment) is estimated at £28 million NPV. Planning balance: +£17.6 million in favour of development, with all mitigation measures in place.


References


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