- Sea level rise adaptation planning is widespread (47/71) in US coastal cities.
- Expert knowledge is widely used (38/47 cities) in sea level rise adaptation planning.
- Neither planning nor the involvement of experts is related to vulnerability.
- Planners request more involvement from physical scientists.
- The most effective experts make scientific research accessible to planners.
Adaptation to sea level rise (SLR) is primarily taking place at the local level, with varied governments grappling with the diverse ways that SLR will affect cities. Interpreting SLR in the context of local planning requires integrating knowledge across many disciplines, and expert knowledge can help planners understand the potential ramifications of decisions. Little research has focused on the role that experts play in local adaptation planning. Understanding how and when local governments undertake adaptation planning, and how scientists and scientific information can be effectively incorporated into the planning process, is vital to guide scientists who wish to engage in the planning process. This study aimed to establish how experts are currently involved in SLR planning, identify any gaps between planners’ needs and expert involvement, and determine the characteristics of experts that are perceived as highly valuable to the planning process. We surveyed individuals involved with planning in a broad range of US coastal communities about SLR planning and the role that experts have played in the process. We found that SLR planning is widespread in cities across geographic regions, population sizes, and population characteristics and has increased rapidly since 2012. Contrary to our expectation, whether a SLR plan existed for each city was not related to the percentage of the population living on vulnerable lands or the property value of those lands. Almost all cities that have engaged in SLR planning involved experts in that process. Planners identify atmospheric scientists, oceanographers, economists and political scientists, and geologists as currently underutilized according to planners’ needs. Members of these expert disciplines, when involved in planning, were also unlikely to be affiliated with the local planning government, but rather came from other governmental and academic institutions. Highly effective experts were identified as making scientific research more accessible and bringing relevant research to the attention of planners. Results from our dataset suggest that planners perceive local SLR planning could benefit from increased involvement of experts, particularly atmospheric scientists, oceanographers, economists and political scientists, and geologists. Since experts in these disciplines were often not affiliated with local governments, increasing the exchange of information between local governments and academic and other (non-local) government organizations could help draw valued experts into the planning process.