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Description: <DIV STYLE="text-align:Left;"><DIV><DIV>SLR Inundation MappingThe topographic data used for this analysis were derived from topographic light detection and ranging (LiDAR) data from NOAA. The SLR inundation mapping was completed on a 1-meter (3.28-feet) digital elevation model (DEM) derived from the bare-earth LiDAR data. The DEM was created by the Port of San Francisco PEC team for the Embarcadero Seawall Program, a component of the Port of San Francisco Waterfront Resilience Program. This data file was developed specifically for the Port of San Francisco planning level program-wide assessment and should not be interpreted as site-specific assessment. For additional details on the DEM development, including modifications to update elevations for piers and wharf structures - see metadata for DEM.The inundation mapping effort leveraged existing and readily available model output from a large-scale MIKE21 San Francisco Bay hydrodynamic modeling effort completed as part of FEMA’s San Francisco Bay Area Coastal Study (DHI 2013). The model takes into account water level variations associated with astronomical tides, storm surge, and El Nino effects. The FEMA model output was used to determine the daily and extreme tide levels throughout the study area for input to the SLR inundation mapping.Inundation maps were developed using the NOAA Coastal Services Center methods (Marcy et al. 2011). The initial step in creating the inundation maps was to create the inundated water surface DEM. Daily and extreme high tide elevations derived from the FEMA MIKE 21 model output points were used to define the water surface elevations for the existing and future conditions MHHW and 100-yr SWEL. The water surface elevations were then extended inland to project the water surface over the inundated topography. Depth of flooding raster files were created by subtracting the land-surface DEM from the water surface DEM. The resultant DEM provides both the inland extent and the depth of inundation in feet. The final step used in creating the depth and extent of flood maps relies on an assessment of hydraulic connectivity. The assessment of hydraulic connectivity removes areas from the inundation zone if they are protected by levees or other topographic features that are not overtopped. DEMThe topographic DEM was revised in 2020 by the POSF PEC to update the best available topographic data for the program area for use in the Multi-Hazard Risk Assessment (MHRA). No new surveying was undertaken as a part of the DEM update. The prior update involved the following:•Identifying recent construction projects which were not captured by the LiDAR Survey conducted in 2010•Utilizing plans provided by the Port of San Francisco (Port) to define the elevations of these projects•Editing the existing DEM based on the available plans•Conducting a general QA/QC of the DEM in the Project areaSummary of updates from the 2010 LiDAR to the AECOM 2016 maps: The existing topographic DEM that will be modified and used in the MHRA was developed based on a 2010 LiDAR survey of the San Francisco coastline. The DEM generated based on the LiDAR survey extended to the Embarcadero promenade and excluded the pier structures within the program area. That DEM, referred to here as the USGS 2010 DEM, was modified for the Port by AECOM (2016) to incorporate the pier structures from Heron’s Head Park to the Golden Gate. The source data for the 2016 update was the raw LiDAR data collected in the USGS 2010 study. AECOM (2016) provides detailed discussion on the methods used to incorporate the pier structures into the USGS 2010 DEM.Summary of updates from AECOM 2016 to MHRA DEM, only for the northern waterfront: The AECOM 2016 DEM was compared to aerial imagery to identify any new construction or demolition which had occurred since the 2010 LiDAR data collection. Based on this comparison several changes to the project area waterfront were identified. These included:•Demolition and reconstruction of the pile supported promenade between Pier 41 and the Franciscan restaurant•Demolition and reconstruction of the Downtown Ferry Terminal•Construction of the Brannan Street Wharf•DEM errors in the overwater areas around Pier ½ and in China Basin•Additionally, based on conversations with the Port, this included the promenade around Pier 1.5.•Increased elevation at footprints of a select few buildings that appeared artificially low and therefore resulting in artificially high damage estimatesBased on available as-built and construction plans the changes in the program area were incorporated in to the AECOM 2016 DEM. Some features along the program area waterfront were identified as a changed condition but not incorporated as it did not impact the potential flood pathways. These included the pedestrian landing and ramp at the Downtown Ferry Terminal and the Park areas at the Cruise Ship Terminal. These omissions were reviewed with the Port and agreed upon prior to completing the DEM updates.Summary of PEC 2021 updates to MHRA DEM:•Incorporated updated ground elevation data from the 2019 aerial photogrammetry survey of the northern waterfront by Chaudhary & Associates. This includes modifications to:•Piers 45, 41½ , 39, 31, 27, 15, 14, 22½, 30, 32, 40, 96•Ferry Building•Brannan Street Wharf•Giants Promenade•Incorporated elevations from the Pier 39 record drawings (1977), Pier 45 Earthquake Repair Project plans (1993), and Pier 96 (southern edge) LiDAR and survey elevations (2015-2016).</DIV></DIV></DIV>

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Copyright Text: Pathways Climate Institute (2022)

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Layer: SanFrancisco_inundation_poly_100yr_84in (ID: 10)