A third‑pass, or detailed, climate change risk assessment provides a deeper, site‑specific understanding of climate change risks. Because this level of assessment can require significant time, expertise, and resources, organisations should first consider whether it is necessary for their context.

Third‑pass assessments are particularly useful for complex or high‑value projects, such as engineering works (e.g. seawalls, groynes, or beach nourishment). In this situation, detailed information on the nature, rate, and extent of climate‑related change is required before progressing to implementation or investment decisions.

A first or second pass risk assessment is appropriate for developing organisation-wide adaptation plans. A third-pass assessment should be used where detailed modelling or hazard studies are required for a complex project (or site) before implementation or investment decision-making.

A third‑pass assessment follows a standard risk‑based framework, similar to a second‑pass assessment, but operates at a higher level of detail. It is not purely quantitative; still essential are qualitative inputs, such as stakeholder judgements on risk evaluation criteria and the relative importance of different risks.

However, for critical systems or where decision‑making demands high precision (e.g. engineering design), some components should be quantitative. For example, a third pass assessment of an at‑risk beach may involve detailed modelling to estimate erosion rates or inundation extents. These results can be used to identify assets at risk and to define trigger points that signal when management actions may be required.

Third‑pass risk assessments can be resource‑intensive, often requiring the commissioning of detailed datasets, specialist studies, and engagement with technical experts or consultants.

Although these assessments increase precision, they do not necessarily improve accuracy, due to ongoing uncertainties in climate projections and sea‑level rise estimates.

Many organisations, particularly smaller councils and businesses, may lack the internal expertise or capacity to undertake all aspects of a third‑pass assessment and will therefore need to engage external consultants. CoastAdapt provides guidance on engaging and working effectively with consultants.

Figure 1 shows the four steps to a third-pass assessment. The process may involve engaging with experts or consultants along with stakeholders from your organisation. Therefore, it’s worth reading some of the relevant content in CoastAdapt.