NORCAL_BIASVALUES - Northern California Shoreline Bias Values

In order to calculate the bias, as well as the bias uncertainty, for this regional shoreline change analysis, long-term best estimates and measures of uncertainty are derived for beach slope, wave height, wave length, and tide level. The best estimate for beach slope was derived by averaging individual lidar transect slope estimates within 1-km blocks along the coast. We take the long-term mean wave height and length to be the best estimate to use in the bias calculation. The long-term mean wave height is derived from USACOE Wave Information Studies (WIS) hindcasts while the long-term mean wave length is derived from long-term buoy records (NDBC and CDIP) along the California Coast. Finally, the best estimate of the tide level responsible for generating HWL shorelines is taken as the elevation of MHW. The measures of uncertainty for the beach slope, wave height, and wave length are estimated as the difference between the 95% exceedance statistic and the 50% exceedance statistic of the cumulative distributions. This gives a 90% confidence interval on each of the cumulative distributions. The uncertainty of assuming that the tide responsible for leaving HWL-type shorelines was at MHW is calculated simply by MHHW-MHW. The proxy-datum bias, and the associated uncertainty, is calculated at each of the 1-km blocks in which the average beach slope has been calculated. The nearest WIS station, wave buoy, and tide gage to each individual 1-km block were used in the application of Equation 1. Once the bias was calculated, it was incorporated into DSAS and applied on a transect-by-transect basis, so that the estimated bias is removed from the final long- and short-term shoreline change rates. The bias, averaged over 815 1-km sections of the California coast, was approximately 18 m with an average uncertainty of approximately 8.7m.
Please See Below References for More information about the procedure:
Ruggiero, P., Kaminsky, G.M., and Gelfenbaum, G., 2003, Linking proxy-based and datum-based shorelines on a high-energy coastline: Implications for shoreline change analyses: Journal of Coastal Research Special Issue 38, p. 57-82.
Moore, L.J., Ruggiero, P.R. and List, J., 2006. Comparing high water line and datum-based shorelines: Implications for shoreline change. Journal of Coastal Research, v.22, n.4, pp. 894-905. Process date is estimated.

Data were projected from UTM zone 10 to geographic with Datum shift from NAD27 to NAD83_6
Tool: ArcGIS > ArcToolbox > Toolboxes > Data Management Tools > Project
Command issued:
['GCS_North_American_1983',DATUM['D_North_American_1983', SPHEROID['GRS_1980',6378137.0,298.257222101]], PRIMEM['Greenwich',0.0],UNIT['Degree',0.0174532925199433]] NAD_1927_To_NAD_1983_6

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