Puget Sound Large River Delta Tidal Restriction and Wetland Mapping
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Cramer Fish Sciences has developed a consistent and comprehensive spatial database of tidal restriction features (e.g., culverts, tide gates, levees, and dikes), and current and potential tidal wetland habitat extents for Puget Sound’s major large river deltas. Although numerous spatial datasets for tidal restriction and wetland habitat currently exist, these have not been synthesized into a consistent regional dataset. In addition, many datasets are incomplete or have become outdated. CFS compiled regional datasets into a consistent spatial database and used remote sensing to update and correct regional data, digitize missing features, and classify feature types and potential connectivity impacts. The resulting spatial database was used to delineate current and potential tidal wetland habitat extents and integrate tidal restriction information. The products of this project are directly supporting salmon recovery planning and evaluation in the Puget Sound region (e.g., ESRP’s River Deltas Learning Objectives, PSP’s Estuaries Vital Sign and Common Chinook Indicators, NOAA’s Salmon Habitat Status and Trends Monitoring Program, and WDFW’s intertidal fish passage assessments) by providing spatial data that can be used to identify and evaluate restoration opportunities, inform development and evaluation of recovery targets at regional and system scales, and identify data gaps to guide future research needs.
Project Goals and Objectives
- Compile available regional tidal restriction datasets into a spatial database with a consistent Coordinate Reference System (CRS).
- Review compiled regional datasets and remote sensing of recent aerial imagery to create a standardized spatial database of tidal restriction features for Puget Sound’s large river deltas (Figure 1) that includes updated, corrected, and missing features based on aerial imagery interpretation.
- Classify tidal connectivity impacts for mapped tidal restriction features based on feature types and aerial imagery interpretation.
- Support the WDFW’s development of field assessment protocols for evaluating barriers to fish passage in intertidal habitats.
- Ground truth and validate the remote sensing approach for identifying missing tidal restriction features, and classifying feature types and connectivity.
- Update regional datasets for current and potential tidal wetland habitat based on the synthesized and updated spatial database of tidal restriction features that integrates classifications of connectivity impacts.
- Make datasets generated as part of this project readily available through online data repositories to support regional salmon recovery planning.
We targeted spatial datasets that contained habitat, infrastructure, and hydrology data for estuarine and delta habitats that include features that block or potentially mute tidal connectivity. Data discovery was focused on spatial datasets for the Puget Sound region and its large river deltas but many state-wide or larger geographical extent datasets were considered. We used two primary methods for data discovery:
- Online searches focused on web-based federal, state, county, tribal, university, and non-governmental sources, and
- Data requests targeting local area experts and regional data stewards.
Online data searches and information on data sources where relevant data were found as well as potential sources where no relevant data were found were documented in a data discovery log. This information will support future updates of the data by providing information on when and what sources were reviewed for relevant data. Contact information and responses were also logged for data request to track information on data acquired from off-line sources.
Additional reference data on stream courses, land cover, wetlands, elevation, and other relevant estuarine habitat information (e.g., not a tidal restriction dataset) were compiled, documented, and considered in the regional data synthesis. These reference data support the classification of tidal wetland extents and correction of alignment and segmentation of tidal restriction features.
Hexagon Imagery Program 0.3 m 4-band aerial imagery collected during summer leaf on conditions from August to September in 2017 were used as our primary reference data for reviewing, correcting, and digitizing missing features, and classifying feature types and connectivity impacts. Other reference datasets used include:
- Google aerial imagery - Provides time series of aerial imagery that can be used to evaluate changes for a feature or reveal attributes not seen in the primary reference image.
- Coastal Atlas oblique shoreline imagery (DOE 2014) - Provides an oblique aerial view for some portions of the nearshore Puget Sound that can provide evidence for feature types or presence.
- Hill shades of digital elevation models - Provides information on the presence and topology of elevated features and channel features where features are obscured by cover or shadows.
- LiDAR available from the Puget Sound LiDAR Consortium - Provides information on the presence and topology of elevated features and channel features where features are obscured by cover or shadows.
- PEMP tidal exceedance polygons (PMEP 2018)- Provides the expected range of tidal influence and informs the potential and current wetland extent based on current topography.
Online Data Sources
UW Washington State - GIS Data Spatial data from comprehensive change analysis for Puget Sound, restrictions, wetland and shoreline features
Initial examination of the compiled regional data found that tidal restriction data layers varied with respect to their extent, methods, geometries, measurements, units, and documentation. Some datasets only included location data for features, while others included attributes that describe physical measurements (e.g., lengths, widths, plunge pool depths, materials used), condition (e.g., present, abandoned, maintained), or fish passage documentation for tidal restrictions. Layers also varied in the geometry (lines versus points) used to depict tidal restrictions (e.g., culverts, levees, bridges) and the spatial accuracy of features. In addition, many features were captured or described by multiple data layers that had differing alignments within small spatial scales, creating problems for regional scale analysis and selection of appropriate data layers. Such variations in data structure, accuracy, and extent limit the usefulness and usability of available datasets at a regional scale and highlight the need for a consistent regional database structure and synthesis of tidal restriction features. Therefore, we created a new data structure that streamlined information, geometry, and attribution from available regional data sources into a uniform spatial framework with key attributes that describe feature types (primary and water crossing structure), tidal connectivity impacts, key physical information, and fish passage information into a consistent spatial database structure.
Standardized Database Structure
Water crossing features
The resulting current and potential tidal wetland network were classified by both their feature tidal connectivity and landscape (downstream) tidal connectivity and included unrestricted, partially restricted, significantly restricted, and completely restricted connectivity ratings similar to the tidal restriction feature connectivity ratings using a rules based classification system. Feature tidal connectivity describes the connectivity of an individual polygon based on only the tidal restriction features that immediately surround or define the polygon perimeter. Landscape (downstream) tidal connectivity considers the connectivity impacts of all of the surrounding and downstream tidal restriction features and wetlands that would impact tidal flow to the wetland feature. Downstream Landscape tidal connectivity was determined by the downstream restrictions or surrounding wetland features allowing tidal connectivity regardless of the presence of less restrictive tidal restrictions or wetlands that immediately surround tidal wetland features. The landscape tidal connectivity of a feature was determined by the connectivity rating of the downstream wetlands and the downstream tidal restriction features. If a restriction had a less restrictive connectivity rating than the downstream wetland, the feature was assigned the wetland connectivity rating. If a restriction had a more restrictive connectivity rating than the downstream wetland, than the wetland was assigned the more restrictive restriction rating.
Local Expert Review and Field Verification
We used a combination of field surveys and local area expert reviews to evaluate errors of omission (e.g., missed features) and commission (e.g., misclassified or misidentified features or impacts) for remotely sensed data (e.g., structure types and connectivity impacts).
Regional experts from county, state, local, and federal agencies were identified using web searches and public communications and outreach, with potential reviewers being asked to review and provide feedback on tidal restriction and wetland layers. Data were uploaded to an ESRI ArcGIS Online data portal that facilitated review and comment by multiple parties.
2. Data structure and utility
Reviews from local area experts increased the efficiency of validation and improve final layer accuracy by leveraging local area knowledge given that field validation surveys are costly and time consuming to implement at a regional scale.
Once field validation and local area expert reviews were completed, feature locations, types, and connectivity ratings were updated for the subset of reviewed features, and certainty ratings were updated to high where appropriate. Information on the source of the updates was also recorded (e.g., reviewer or field validation), as well as the feedback (e.g., feature missing from database, feature misclassified, feature restored), date, and the actions taken (e.g., re-classified in database, feature moved, further evaluation needed). We also used the regional review and field survey data to evaluate and report classification accuracy metrics and error rates (e.g., errors of omission and commission) to evaluate our aerial imagery based remote sensing approach.
Field validation focused primarily on unknown and aerial imagery identified water crossings, with a small subset aimed at verifying aerial imagery mapped dike/levee features. A total of 189 tidal restrictions, including 38 primary and 151 water crossing features were field verified.
Collectively, overall classification accuracy for features mapped to type (e.g., features that were not classified as unknowns or otherwise flagged for review after remote sensing and regional data synthesis) from using both the aerial imagery and regional data was 10% (38/372) for regional expert reviewed features and 50% (46/92) for field verified features. However, it should be noted that regional review was not conducted as a census of features and was performed based on the reviewer’s area of expertise and therefore reviews were largely targeted at features that were misidentified, as opposed to verified.
Mapping efforts for tidal restrictions and tidal wetlands for 17 large river deltas were completed using compiled regional data sets and 2017 aerial imagery. Therefore, the resulting layers reflect information and conditions up through 2017 and do not reflect restoration (e.g., reaches or dike setbacks), development (e.g., filling, development, or diking), or natural changes (e.g., avulsions or delta progradation) that have occurred since then, unless documented in the regional data or in the review.
Final Report and Data Access
Link to the WDFW hosted web maps and data download.
The tidal wetland data produced from this project are also being used to support the PSP Vital Signs Estuaries Indicator for the Estuary Area in Functional Condition. More information on the indicator status and Vital Signs program is available here and the full indicator report is available here.
Please contact Jason Hall (email@example.com) or Shelby Burgess (firstname.lastname@example.org) with any questions regarding this project.