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Layer: Tier 1: Historic Shoreforms (ID: 3)

Name: Tier 1: Historic Shoreforms

Display Field: SUBBASIN

Type: Feature Layer

Geometry Type: esriGeometryPolyline

Description: Shoreform is a term often used in Puget Sound to describe a coastal landform. The term is generally used to describe landscape features on the scale of hundreds to thousands of meters in scale, such as coastal bluffs, estuaries, barrier beaches, or river deltas.The shoreform change data are a compilation of current and historic shoreforms applied to the ShoreZone shoreline. Historic and current shoreforms in Puget Sound were independently delineated and combined onto a single shoreline (ShoreZone) to provide a comparison of historic to current conditions.Translation of Current Shoreform to Shipman TypeThe current ShoreZone shoreline was classified according to a geomorphic classification system developed by McBride et al. (2005) and applied by SSHIAP (Todd et al. 2009). Because the shoreform classification system chosen for the Change Analysis is Shipman (2008), the current shoreline types (GeoUnits) had to be cross‐walked to the corresponding Shipman types. Some of the SSHIAP types may correspond to more than one Shipman type, so a first‐cut, automated translation was performed. The Shipman type assigned during the automated translation was the class expected to be correct most of time. There is no SSHIAP GeoUnit that corresponds to Shipman’s Open Coastal Inlet (OCI) shoreform in the automated translation process.This automated translation was followed by a visual review of all current shoreforms to make any necessary modifications to the current shoreform type.Simultaneous Review of Current and Historic ShoreformsAfter translation of the current shoreline type into the Shipman type, both current and historic shoreforms were displayed using the same symbology and edited as necessary. This review was performed in order to:• Assign the correct type to the current shoreform for GeoUnit types that may correspond to more than one Shipman type.• QC current and historic shoreform types and modify values as necessary.• Split historic shoreform segments when necessary to correspond to a region of change from historic to current.The review of historic and current shoreforms was guided by a list of expected shoreform transitions. These expected transitions were based on Shipman’s Transition Narrative (7/31/2007) and review of results in Whidbey and South Puget Sound sub‐basins. Any shoreform change not specified on this list was subject to additional scrutiny.Because of the difference in approaches and classification methods, if there were ambiguities in classification, it was more important to determine whether a section of shoreline had changed than to try to determine the “correct” type. The following general rules were applied:• If there was clearly no shoreline change, but the two shoreform types differed, the historic shoreform type was used for both current and historic.• If there was a question about where to place breaks for shoreline change, (because only part of a contiguous shoreform type had changed), the current shoreline was used as a guide.• Unless there was a shoreform change or obvious error, segment end point locations, in both the current and historic shoreline, were not changed.Attribute Transfer from Historic to Current ShorelineAfter historic and current linework were reviewed, the attributes from the historic shoreform data were transferred to the corresponding segments of the current shoreline. Once this process was complete, and the final data were intersected with the GSUs, it was possible to query each segment of the current shoreform data and find the historic shoreform type and its full length, or the length that was included within a specific GSU.This process entailed the following:• Assignment of a unique identifier to each section of contiguous historic shoreform.• Assignment of a unique identifier to each section of historic shoreline that will correspond to a section of current. (A contiguous section of a single shoreform type may be split due modification of part of that shoreline in modern times.)• Assignment of a unique identifier to each section of current shoreform.• Transfer of the historic shoreform type and its length to attributes in the corresponding current shoreline segment.On-line and Off-line EmbaymentsThe current shoreline (ShoreZone) does not depict all of the current estuarine wetlands or embayments (BE, BL, CLM). To handle this discrepancy, an additional attribute in the current linework indicates the presence of these features as “off‐line” wetlands and identifies their shoreform type.If the current embayment was delineated by the shoreline linework, the corresponding historic embayment attributes were transferred to the primary (“on‐line”) historic shoreform fields. If the current embayment was not delineated by the shoreline linework, the corresponding historic embayment attributes were transferred to the embayment (“off‐line”) shoreform columns.The length of the current off‐line embayment was transferred from the University of Washington Puget Sound River History Project current wetlands data. The criteria for including a wetland boundary as part of the historic embayment were based on the same rules used for historic shoreform delineation.Off‐line embayment attributes were assigned to an entire homogeneous section of shoreline. The on‐line shoreform was not split to indicate exactly where the off‐line embayment occurs. It was adequate to know that there was (or is) an embayment associated with that stretch of beach.NST Review (Fly-Bys)Shoreform change data for each sub‐basin were reviewed during a half‐day meeting with a minimum of three NST members present, as well as participants from SSHIAP. The participants viewed current shoreforms, historic shoreforms, and the combined data with ancillary and source datasets, including historic T‐sheets, aerial photos, and historic and current wetlands data. The reviews, called “fly‐bys,” had the following objectives:• Provide the NST with an understanding of the historic and current shoreform data and the process used to develop shoreform change data.• Get input from the NST on question areas, either site‐specific or general methodological questions.• Review all areas of shoreform transition as a QC measure.• Review any other areas of interest specified by the NST.• Develop or refine rules for situations of ambiguity in shoreform classification or shoreform change data developmentOverall, the NST reviewed approximately 58 percent (2,250 km) of the total shoreline length. The discussions at these meetings were iterative, and sometimes a general rule developed at a previous meeting was reversed in a later meeting as participants became more familiar with the data, the process, and had more examples for consideration. The general rules and methods that came out of these fly‐bys are described below.Expected Transitions MatrixThe NST representatives reviewed a matrix of expected shoreform transitions at the first fly‐by. Transitions that were not in this matrix were flagged during the QC process, and were given particular attention during review. The NST approved this list and it was subsequently updated in later fly‐bys. Barrier Beach Merge or SplitFor barrier beaches that were discontinuous in one dataset (due to an on‐line embayment) and continuous in the other (due to an off‐line embayment), the NST representatives approved this general rule: if the drift is the same direction, merge the discontinuous segments into one; if the drift is in opposite directions, split the continuous segment into two.Created ShoreformIt was acceptable to have shoreline in the current shoreform that was not in the historic. These were assigned the Artificial (ART) shoreform. Examples in Whidbey sub‐basin include Jetty Island at the mouth of the Snohomish River and a small “island” (of dredge material) at the southern end of the Swinomish Slough.Current Shoreline PositionSometimes the current shoreline (ShoreZone) mapped the backshore area, and the on‐line and off‐line shoreforms were the opposite of how they were mapped in the historic. When this occurred, they were swapped so that the beach shoreform was assigned to the line, and any embayment shoreform was off‐line.Rocky Shoreline in Current, not HistoricOften there were small bedrock islands that were mapped in the current shoreform, but not in the historic. It was assumed that the rock existed previously, but was not mapped on the historic T‐sheets. Therefore, it was not a true transition. The NST requested that shoreforms stay the same to reflect the source data (rocky in current and none in historic), but that it should not show up as a transition.Artificial/Modified ShorelineThere was extensive discussion regarding the definition of an artificial or modified shoreline. It was decided that the term Artificial was preferred to Modified. The definition is not based on function, rather it is based on the extent of obvious modification, such as dredging and fill. This extent can be determined by use of ancillary layers showing fill, or by areas where the shape and location of the shoreline has changed significantly. (Significant change was not rigorously defined, so some subjectivity is involved in classification of Artificial shoreforms.) In the case of railroads, although there may have been some fill involved, in many cases, these shoreforms were not significantly changed in location, shape, or visible processes from the historic shoreform, and therefore were classified as a non‐artificial beach type (such as Bluff‐backed Beach). Road causeways that were commonly built along former spits across the mouths of embayments were mapped as Artificial (ART) along the outside and the inside of the causeway. If the rest of the embayment was not artificial, it was mapped as the appropriate embayment type.Data SynthesisAfter the review meeting, any changes requested during the fly‐by were implemented. The changes were documented in a notes field in the attribute table.Two fields were added to aid in the display of on‐and off‐line transitions.Once the historic and current shoreform typologies on the current shoreline were finalized, the data were intersected with the GSU data. Because the shoreform delineation was an independent process from the GSUs, the lengths of each feature split up by the GSUs was calculated after this intersection step using lengths stored in the attribute table prior to intersection. The proportional lengths apply to both current and historic shoreforms, both on and off the ShoreZone shoreline. To accomplish this, the following calculations were performed:• Current on‐line shoreform GSU lengths are equal to the Shape Length calculated by the geodatabase. (C_LenGSU = Shape_Length)• Current off‐line embayment shoreform lengths are equal to the pre‐intersection total embayment length multiplied by the pre‐and post‐intersection length ratio (C_LenEmbGSU = C_LenEmb * C_LenGSU / C_LenFull)• Historic on‐line shoreform GSU lengths are equal to the transferred continuous shoreform length multiplied by the pre‐and post‐intersection length ratio (H_LenGSU = H_LenFull * C_LenGSU / C_LenFull)• Historic off‐line embayment shoreform lengths are equal to the pre‐intersection total embayment length multiplied by the pre‐and post‐intersection length ratio (C_LenEmbGSU = C_LenEmb * C_LenGSU / C_LenFull)These GSU lengths are ultimately used to calculate historic and current shoreform lengths at multiple scales. During QC, these fields were also compared against the historic shoreform data in a series of tabular queries to verify that all historic shoreformsand their lengths were correctly transferred into the shoreform change attribute table.Fields representing the percent change in length for both on‐and off‐line features were calculated as follows:• Chg_PropLen_OnLine = (C_LenFull – H_LenFull)/H_LenFull• Chg_PropLen_OffLine = (C_LenEmb – H_LenEmb/H_LenEmbThese percent changes in length reflect complete losses of shoreforms as well as lost lengths in shoreform.The extensive review and QC applied to these data indicate that they are quite accurate and consistent between sub‐basins. The shoreform data were developed specifically for the Change Analysis, so will be appropriate for project‐specific analyses.

Copyright Text: Simenstad, C.A., M. Ramirez, J. Burke, M. Logsdon, H. Shipman, C. Tanner, J. Toft, B. Craig, C. Davis, J. Fung, P. Bloch, K. Fresh, S. Campbell, D. Myers, E. Iverson, A. Bailey, P. Schlenger, C. Kiblinger, P. Myre, W. Gerstel, and A. MacLennan. 2011. Historical Change of Puget Sound Shorelines: Puget Sound Nearshore Ecosystem Project Change Analysis. Puget Sound Nearshore Report No. 2011-01. Published by Washington Department of Fish and Wildlife, Olympia, Washington, and U.S. Army Corps of Engineers, Seattle, Washington.

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