The rock, wood and concrete protective walls that shield the east shore of Tomales Bay from rising seas are the subject of a new vulnerability report presented to Marshall residents last week. The Marin County Community Development Agency has completed a draft of the Tomales Bay Bulkhead Vulnerability Assessment, which analyzes sea barriers, from riprap buttresses to manmade earth embankments, along the five-mile section of shoreline from the Marconi Conference Center to Nick’s Cove.