San Francisco Bay Joint Venture (SFBJV) 'baseline' Transition Zone (for SF, San Pablo and Suisun bays)

The GIS dataset represents the ‘baseline’ distribution and acreage of estuarine-upland transition zone elevations that are both (a) exposed to tides; and (b) adjacent to a saline marsh. The baseline data can be used to track changes to transition zone distribution and acreage over time. The GIS dataset not only represents the current baseline distribution of transition zone, but also distinguishes between transition zone that is either in the ‘backshore’ (adjacent to both a tidal wetland and an upland) or in the ‘mid marsh’ (only adjacent to a tidal wetland).

The SFBJV baseline transition zone GIS dataset is derived from the ‘Bay Margin’ estuarine-upland transition zone decision support system (DSS) funded by the USFWS and California Coastal Conservancy. See http://climate.calcommons.org/dataset/san-francisco-bay-estuarine-terrestrial-transitional-zone-decision-support-system for more information on the DSS.

Included in the metadata is an overview of the steps taken to modify and improve the current transition zone distribution (and rankings) layer in order to establish a ‘baseline’ for transition zone acreage through the SFBJV area of responsibility. The SFBJV baseline transition zone GIS layer differs from the original dataset in that it contains only transition zone, that: (1) is exposed to tides (“actual” transition zone); and (2) is adjacent to a saline emergent wetland. The resulting SFBJV baseline transition zone GIS layer is considered to represent ‘actual’ existing transition zone distributions (ie transitional elevations exposed to tidal action and adjacent to saline marsh) in SF, San Pablo and Suisun bays.

Although the SFBJV 'baseline' transition zone is considered to represent "current conditions" (July, 2018) it utilizes GIS datasets from a wide range of dates. These datsets include: NOAA (C-CAP, 2010), CDFW (CalVeg, 2007/14), NOAA/USGS (2m BathyTopo Lidar, ~2010), NOAA (tides and currents), Point Blue (tidal/non-tidal mask, ~2010), and GreenInfo (CPAD). The distribution and quality of transition zone are based on GIS models that use best available (and the most recent) tidal and habitat datasets. As a result, the accuracy of the baseline transition zone layer produced from this process is only as good as the underlying datasets used in our model.