Puget Sound Marine Riparian Mapping

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The primary goal of this project is to support regional salmon recovery planning and evaluation by developing regionally consistent and up to date spatial data layers for tidally influenced and marine riparian habitats at the regional scale. To achieve this goal, we will work with salmon recovery agencies to develop spatial data products that leverage and integrate with existing habitat status and trends monitoring programs and metrics, address regional data gaps, and are readily accessible through online mapping applications to support restoration planning and evaluation of progress towards recovery at a regional scale. This project will include two key objectives that are described in the project plan; (1) creating a consistent and up to date regional spatial database of tidal restriction and tidal wetland features, and (2) mapping marine riparian cover width for Puget Sound for two time steps. This page focuses on describing the efforts to map marine riparian habitat. More information about the tidal restriction mapping can be found on the Puget Sound Large River Delta Tidal Restriction and Wetland Mapping and the Puget Sound Tidal Restriction and Wetland Mapping pages.

Project Goals and Objectives[edit]

  • Summarize percent forested cover using a selected shoreline dataset to generate 0-100 ft and 0-200 ft buffers for 2013 and 2017.
  • Segment a corrected shoreline with breaks based on contiguous forested cover width classes and shoreform types for 2009 and 2017.
  • Conduct regional review and ground truthing to update and evaluate data accuracy.
  • Summarize marine riparian extent and percent forested cover metrics by geographical areas (e.g., marine basin, Lead Entity (LE) and Chinook Recovery Watershed (CRW) boundaries), shoreform, and width classes for two time periods, evaluate trends, and compare methods to support regional habitat status and trends monitoring reporting.

Background[edit]

The extent and condition of marine riparian habitat influences its function (e.g., sediment/erosion, shading, nutrient flux, prey inputs) and represents an important indicator for species that rely on nearshore habitats (e.g., juvenile salmonids, forage fish) (Shreffler et al. 1994; Brennan & Culverwell 2004; Brennan et al. 2009). Marine riparian functions are attenuated with distance from intact marine forests and can be impaired by discontinuities (Desbonnet et al. 1995, Brennan et al. 2009).

For the purposes of describing marine riparian habitat, we will consider riparian zones of influence or contiguous widths that describe a functional area of a riparian habitat as opposed to a regulatory boundary (e.g., buffer or critical area). The width, seral stage, and composition of riparian systems in nearshore marine systems can influence the function of riparian habitats much like that which is observed in freshwater systems (e.g., sediment, bank stability/erosion, shading/thermal, nutrient flux, terrestrial invertebrate inputs) (Desbonnet et al. 1995; Brennan et al. 2009). The degree to which these functions are supported by riparian habitats generally attenuates with distance from the shoreline or bank, such that most functions of a riparian system are maintained by the zones closest to the shoreline and/or bank.

The riparian zone of influence includes the band or zone of riparian habitats that would provide most of the desired riparian functions along a shoreline if fully intact. Most ecological functions of a riparian system are maintained within 0–100 ft of the shoreline, assuming the riparian system is intact, but width of riparian habitat recommended by the PSEMP NSWG (2019) for undeveloped shoreline is 200-ft.

We worked with the Marine Riparian TAG to determine the riparian zones of influence and datasets to use to derive percent and contiguous marine riparian cover metrics, to determine which shoreline data to use, and to discuss how the marine riparian spatial data can be linked to the ESRP Beach Strategies NGF layers that are being used to support other regional salmon recovery planning activities.

Methods[edit]

Metrics describing the functional condition of marine riparian habitat have been developed for regional habitat status and trends monitoring programs (including National Oceanic and Atmospheric Administration (NOAA)'s Salmon Habitat Status and Trends Monitoring (SHSTMP) , Puget Sound Partnership (PSP)'s Common Indicator and Vital Signs), and protocols and preliminary regional data were developed in a previous project in coordination with NOAA, PSP, and Puget Sound Ecosystem Monitoring Program (PSEMP) (Hall et al. 2019; PSEMP NSWG 2019).

As part of this project, we will refine and implement protocol recommendations from the PSEMP NSWG workshop on marine riparian habitats (2019) to map percent and contiguous forested riparian cover for two time steps. This will allow comparison of protocols and reporting of habitat status and trends metrics for marine riparian function at a regional scale.

Width of contiguous forested cover

Example of forest width class measurement along No Appreciable Drift - Bedrock shoreform in oblique imagery (DOE 2018). Shoreline sections marked in red are classified as no forest due to the height at which forested cover begins. Shoreline sections marked in blue and purple are classified as 30-60 and 100-150 ft width classes, respectively, as a natural break in forested cover is present. The orange shoreline sections represent measurements of forested cover widths greater than 200 ft.

The contiguous marine forested cover metric is being developed by NOAA NWFSC. The contiguous marine forested cover layer will be generated by segmenting and attributing an up-to-date shoreline layer with the binned width of forested cover at that segment, determined by interpreting aerial (e.g., National Agriculture Imagery Program (NAIP), Google Earth) and oblique shoreline imagery (e.g., Department of Ecology (DOE), EarthViews), and LiDAR-derived DTMs and digital surface models (DSM) to determine the extent of forested cover from the shoreline. This includes both coniferous and deciduous species, but height criteria would not be used as the delineation would be based on aerial imagery interpretation. The objective is to map cover for trees within a similar range of heights, which may include a mix of species (e.g., deciduous and coniferous), forms (e.g., tall shrubs and trees), and seral stages and would assume equal functional condition for mixed stands.

Currently, two geospatial datasets are available that describe shoreline in the Puget Sound: The National Oceanic and Atmospheric Administration Continuously Updated Shoreline Product (NOAA CUSP) and the Washington Department of Natural Resources (WDNR) ShoreZone (WDNR, 2001; NOAA 2021). While many regional data products rely on these shoreline layers, both are unsuitable for measurement of marine riparian forested cover due to age, known alignment errors, or inappropriate tidal datum reference. As a result, the first step of our approach is the development of an updated shoreline layer describing the Ordinary High Water Mark (OHWM), by following the methods described in Anderson et al. (2016) and using LiDAR-derived hillshade digital terrain models (DTM) and aerial and oblique imagery for reference.

The shoreline will be segmented by the the width of contiguous forested cover and classified by width class (no forest- developed, no forest within 200 ft, 0-30 ft, 30-60 ft, 60-100 ft, 100-150 ft, 150-200 ft, and 200+ ft). Shoreform will also be identified and will inform the seaward extent of forest mapping.

Two years were identified to evaluate trends in the contiguous forested cover within Puget Sound, 2009 and 2017. We selected 2009 because it is the earliest year of NAIP imagery with 4-bands, including near-infrared. We selected the 2017 aerial imagery to match the imagery year of a parallel effort to map the percent of forested cover. The layer for 2017 aerial imagery will be developed first, as coverage of higher quality lidar is more extensive for that time period, ranging from 2014 to 2020. Subsequently, we will adjust the 2017 data to the 2009 aerial imagery, with sources of shoreline change between years identified in the attribute table.

The draft monitoring protocol developed by the NWFSC are available here.

Percent forested cover

The percent forested cover dataset will be generated by Cramer Fish Sciences. This metric calculates the percent and total area of forested cover within riparian zones of influence for the entire Puget Sound shoreline based on the extent of forested cover classes derived from high-resolution land cover (HRLC) datasets (Pierce 2019). The HRLC datasets map forested cover based on classification of cover types and height differences from bare earth elevation models. In the HRLC datasets, forested cover includes classifications of coarse, medium, and low trees, and tree cover types, and does not differentiate species or seral stage. In general, these data allow us to represent the percent coverage of vegetation that is approximately 10 ft or taller and represents medium and large coniferous and deciduous trees. Similar to the contiguous approach, this approach will assume equal riparian function for mixed stands but the functional threshold required for percent forested cover has not been defined.

The preliminary protocol and regional data were developed using the Washington Department of Natural Resources (WDNR) ShoreZone shoreline (2001), 2011 High Resolution Land Cover (HRLC) data (Pierce 2015), and the ESRP Beach Strategies for Nearshore Restoration and Protection in Puget Sound 100-ft and 200-ft shoreline buffers to quantify percent forested cover by shoreform and Lead Entity boundaries. This provided a single snapshot of marine riparian condition for the region and this was generated from datasets that rely on the Washington Department of National Resources (WDNR) ShoreZone shoreline that has known alignment errors. Therefore, protocol recommendations developed through the PSEMP Nearshore Spatial Data Work Group (NSWG) (2019) and described in Hall et al. 2019 included developing a corrected shoreline and segmenting the shoreline based on contiguous forested cover rather than percent forested cover within riparian zones of influence.

The processing workflow described for the percent forested cover metric relies on GIS to attribute the 2017 HRLC data (Pierce 2015, 2019) with the counts of classified raster land cover, derived through zonal statistics analysis, for each of the shoreforms within the ESRP Beach Strategies NGF polygons (0–100 ft, 0–200 ft, and 100–200 ft riparian zones of influence).

Based on the input from the TAG and recommendations in the previously developed protocol, mapping for this project will use the shoreline developed for mapping the width of contiguous forested, but will use the same buffers (0-100 ft, 0-200 ft, and 100-200 ft) used in the previous protocol.

Percent forested cover for 2017 was mapped in Hall et al. (2019). This mapping effort will re-calculate the 2017 data using the updated shoreline, as well as map percent forested cover within the shoreline buffers using the 2013 HRLC. This will allow us to compare changes between years, as well as compare our results to the WDFW high-resolution change detection dataset (HRCD), which also evaluated between 2013 and 2017 (Pierce 2019).

Mapping status[edit]

Mapping of the updated shoreline and contiguous marine riparian cover is currently underway by NWFSC, mapping of percent forested cover will begin once the marine riparian shoreline is completed for a given Chinook Recovery Watershed.

Notes[edit]

  • This project was funded as part of an ESRP/Learning Program (PRISM Project #20-1941).
  • The project was contracted in 2021 and a final report will be delivered in the early winter of 2024.
  • Data products developed as part of this project will be made available through WDFW hosting and will be linked to on this page.
  • PRISM Project #20-1941 contract and documents

Please contact Jason Hall (jason.hall@fishsciences.net) with any questions regarding this project.

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