This report presents the results of a benefit cost analysis of various options for adapting West Cliff Drive (in the City of Santa Cruz, California) to sea level rise as identified through extensive technical analysis and community input. This report has built on previous work completed as part of the West Cliff Drive Adaptation and Management Plan project. The previous work products provided much of the information needed for this benefit cost analysis included an existing conditions inventory, future exposure and vulnerability assessment, and an adaptation alternatives analysis. Since most of the West Cliff Drive corridor is publicly owned by the City of Santa Cruz and California State Parks, results of the future exposure and vulnerability assessment showed that little private property and only small portions of public infrastructure is at risk in the future. Thus, the benefit cost analysis focuses primarily on changes to the recreational uses of the West Cliff Drive corridor.
One challenge to adaptation planning is the uncertainty associated with the rate and elevation of sea level rise at future points of time, critical to the question of what to do and when. To deal with this uncertainty, the benefit cost analysis uses a technique called Monte Carlo analysis, a technique to test many different possible scenarios of sea level rise; in this analysis, 100,000 different scenarios were examined in every run of the analysis. The underlying sea level rise data is the same as used by the State of California in its various sea level rise planning guidance documents. This approach to the benefit cost analysis allows an estimate not only of net benefits but also the probability of positive net benefits of each adaptation strategy.
The purpose of this benefit cost analysis is to compare the economic benefits and costs of the coastal adaptation options aimed at managing coastal erosion to a future in which no additional adaptation actions beyond those routinely taken by the City are taken. The benefit cost analysis is designed to support a choice between those different adaptation strategies which involve substantial new expenditures by the City the or “business as usual” strategy. The fundamental question is whether it is economically worthwhile for the City to invest substantial resources in adapting to sea level rise along West Cliff Drive compared with continuing as they have in the past? Economically worthwhile projects have benefits greater than costs, taking into account the differences in timing of spending and receipt of benefits. This concept is called the net present value.
Four scenarios are examined:
- Business as Usual – No actions are taken beyond routine maintenance and irregular emergency repairs
- Managed Retreat – Existing armoring structures are removed, and natural erosion and shoreline processes restored.
- Recreation Focused Strategy – A combination of sand management, reduction in coastal armoring footprints and sand retention structures along with structural adaptation in high hazard areas such as sea caves.
- Protection Focused Strategy – Projects that stabilize the shoreline such as revetments, seawalls, filling of sea caves, and construction of artificial bedrock.
Colgan, Charles S., King, Philip, Revell, David, "Benefits Cost Analysis: Options for Sea Level Rise Adaptation on West Cliff Drive," October 8, 2020, prepared for the City of Santa Cruz.