Evaluating methods to obtain high resolution nearshore bathymetry and coastal topography for Puget Sound

The Washington State Department of Ecology Coastal Monitoring & Analysis Program performed a coastal topographic and bathymetric survey of Port Gamble Bay between March 9 and March 28, 2014. Boat-based topographic lidar was collected along the shoreline of the bay and multibeam bathymetric sonar was collected throughout the bay to obtain a seamless topographic-bathymetric surface with complete coverage of Port Gamble Bay. The survey was performed with a R2Sonic 2022 multibeam echosounder, an Optech ILRIS-HD-ER mobile laser scanner, and an Applanix POS MV 320 v5 receiving real-time kinematic positioning corrections. The Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX) performed a topographic and bathymetric lidar survey of Port Gamble Bay on September 4, 2014. The Coastal Zone Mapping and Imaging Lidar (CZMIL) system was used to obtain seamless coastal topographic-bathymetric coastal intertidal and nearshore coverage of Port Gamble Bay. The bathymetric depth coverage is limited to laser extinction, which is determined by water clarity. The availability of these two datasets provides the unique opportunity to compare data between high-resolution boat-based lidar and multibeam systems and the state-of-the-art airborne topo-bathy lidar system and also assess detection and resolution of specific features throughout a range of water depths across the nearshore important to habitat and restoration efforts. This effort provides a detailed comparison of coverage and resolution of nearshore features and will help clarify differences between these capabilities to aid in planning complementary efforts in coastal zone mapping and monitoring

High resolution mapping of Puget Sound shorelines

In an effort to collect high-resolution baseline coastal topographic data of beaches and bluffs around the Puget Sound and Strait of Juan de Fuca, the Washington State Department of Ecology Coastal Monitoring & Analysis Program (CMAP) conducted a series of boat-based lidar surveys in October 2013, May through September 2015, and May 2016 at a total of 16 sites spanning 220 km of shoreline and over two dozen drift cells. The drift cells were selected based on a rigorous and systematic geospatial analysis of bluff-backed beaches for their potential for significant bluff sediment supply to intact shorelines identified as having a relative abundance of habitat for forage fish, eelgrass, herring, shellfish, and geoduck, as well as having previous investments in beach restoration projects, and potential for future shoreline armoring and habitat loss based on population growth scenarios. As such, the surveyed drift cells are top candidates for implementing drift cell-scale protection and restoration strategies. The boat-based lidar and GPS topography data were used to produce 0.5-m digital elevation models (DEMs) for the beaches and bluffs at each of the survey sites. These DEMs provide the opportunity to inventory and characterize the shoreline landscape that affects nearshore ecosystem services such as feeder bluff activity, beach slope and width, and the position, length, and elevation of armoring relative to the backshore. Boat-based lidar provides an advantageous point of view of the bluff face, resulting in high resolution data which is needed to gain insight into bluff failure and erosion mechanisms and corresponding sediment transport processes. In addition, it successfully collects data under overhanging vegetation and overwater structures. Repeat surveys in the future would enable change analyses for quantifying bluff sediment supply, changes in marine riparian vegetation, and a better understanding of the linkages between physical and ecological processes

Assessing bulkhead removal and shoreline restoration using boat-based lidar

The Washington State Department of Ecology performed before and after boat-based lidar surveys of a shoreline restoration project involving the removal of ~800 feet of armoring from the base of a historic feeder bluff at Edgewater Beach, along Eld Inlet in South Puget Sound. As part of the restoration project, 700 feet of bulkheads, two rock revetments, a large wood and rock groin, and several large boulders were removed or realigned from the site in fall 2016. Removal of the armoring is expected to reconnect the historic feeder bluff at the updrift end of the project site with the adjacent beaches, restoring nearshore habitat and sediment supply to the drift cell. This poster will present an assessment of geomorphological changes to the beach and bluff associated with the bulkhead removal, and the opportunity to utilize this monitoring technology for documenting the physical processes and habitat functions restored through projects of this type

Historical evolution of the Columbia River littoral cell

This paper details the historical coastal evolution of the Columbia River littoral cell in the Pacific Northwest of the United States. Geological data from A.D. 1700 and records leading up to the late 1800s provide insights to the natural system dynamics prior to significant human intervention, most notably jetty construction between 1885 and 1917. All reliable surveys, charts, and aerial photos are used to quantify decadal-scale changes at the three estuary entrances and four sub-cells of the littoral cell. Shoreline, bathymetric, and topographic change over three historical intervals—1870s–1920s, 1920s–1950s, and 1950s–1990s—are integrated to provide an understanding of sediment-sharing relationships among the littoral cell components. Regional morphological change data are developed for alongshore segments of approximately 5 km, enabling comparisons of shoreline change to upper-shoreface and barrier volume change within common compartments. The construction of entrance jetties at the Columbia River (1885–1917) and Grays Harbor (1898–1916) has profoundly affected the evolution of the littoral cell, and has accentuated the morphological coupling between the inlets, ebb-tidal deltas, shorefaces, and barriers. The jetties induced erosion of the inlets and offshore migration of ebb-tidal deltas. The change in boundary conditions at the entrances enabled waves to rework the flanks of ebb-tidal deltas and supply enormous quantities of sand to the adjacent coasts. Over several decades the initial sand pulses have been dispersed alongshore up to tens of kilometers from the estuary entrances. Winter waves and coastal currents produce net northward sediment transport across the shoreface while summer conditions tend to induce onshore sediment transport and accumulation of the upper shoreface and barriers at relatively high rates. Historical shoreline progradation rates since jetty construction are approximately double the late prehistoric rates between Kaminsky et al., MGSI 3 of 107 9/15/2009 1700 and the 1870s. Erosion rates of the mid- to lower shoreface to the south of the jettied estuary entrances have typically been greater than the accumulation rates of the upper shoreface and barrier, suggesting that the lower shoreface has been an important source of littoral sediments over decadal and longer time scales. Until recent decades, sediment supply from the ebb-tidal delta flanks and lower shoreface has largely masked the decline in Columbia River sediment supply due to flow regulation and dredging disposal practices. With the contemporary onset and expansion of coastal erosion adjacent to the jettied estuary entrances, proper management of dredged sediment is imperative to mitigate the effects of a declining sediment budget.Keywords: Washington State, Columbia River littoral cell, coastal evolution, sediment budget, shoreline change, large-scale coastal behavior, Oregon Stat

Extreme oceanographic forcing and coastal response due to the 2015-2016 El Nino

The El Niño-Southern Oscillation is the dominant mode of interannual climate variability across the Pacific Ocean basin, with influence on the global climate. The two end members of the cycle, El Niño and La Niña, force anomalous oceanographic conditions and coastal response along the Pacific margin, exposing many heavily populated regions to increased coastal flooding and erosion hazards. However, a quantitative record of coastal impacts is spatially limited and temporally restricted to only the most recent events. Here we report on the oceanographic forcing and coastal response of the 2015–2016 El Niño, one of the strongest of the last 145 years. We show that winter wave energy equalled or exceeded measured historical maxima across the US West Coast, corresponding to anomalously large beach erosion across the region. Shorelines in many areas retreated beyond previously measured landward extremes, particularly along the sediment-starved California coast

A geospatial approach to prioritizing drift cells for strategic protection, restoration, and enhancement

The Washington Department of Ecology Coastal Monitoring & Analysis Program has developed an objective, systematic, and data-based approach to identifying and prioritizing intact shorelines (drift cells) that offer a high potential for learning, protection, and restoration, combined with a convergence of stakeholder interest and institutional capacity for collaborative nearshore ecosystem management. The approach and current criteria used identifies highest-priority drift cells with feeder bluffs that actively provide sediment to the nearshore and sustain an unusually high level of ecosystem services. The approach is intended to serve as a model for determining where in the landscape to strategically invest capital and social inputs for protection and restoration efforts. Spatial analysis of widely available physical, ecological, and social data and the use of multiple criteria, metrics, and their relative weighting provide initial assessment of high-value locations, while site monitoring, characterization, and geomorphic change analysis can provide refined information to guide the specific approach to ecosystem management for each site. With over 1000 drift cells in Puget Sound, the current project identified 17 ‘top-tier’ and 24 ‘second-tier’ drift cells as well as 105 ‘third-tier’ drift cells that represent 163, 143, and 406 km of shoreline, respectively. The drift cells within the ‘top-tier’ category are predominantly located in north Puget Sound; only one site is located in south central or south Puget Sound sub-basins, whereas 8 of the 24 ‘second-tier’ sites are located in these southern basins. The current criteria used emphasizes drift cells that offer the greatest potential return on ecosystem services per quantity of capital and social investment, thus there is an inherent bias toward projects involving protection over restoration. However, given the anthropogenic overlay and influence on the landscape, opportunities for restoration are essentially ubiquitous

Initial characterization and comparison of beach sediment throughout Puget Sound

An understanding of the sediment grain size distribution of a beach provides important information about its physical properties and ecological functions. Forage fish are a diverse assemblage of species that serve as an essential component to the marine food web. The ability of forage fish to produce viable spawn is dependent on the grain size present. Surf smelt Hypomesus pretiosus and Pacific sand lance Ammodytes hexapterus utilize sediment within a unique grain size range as a spawning substrate. Pacific herring Clupea pallasii are known to utilize native eelgrass Zostera marina as a spawning substrate, which grows in fine sediment-supported nearshore environments. Sediment grain size data can also provide information related to shoreline armoring impacts, feeder bluff activity, and the sediment budget of a littoral drift cell, which can help to inform land-use and resource management decisions. The Washington Department of Ecology Coastal Monitoring & Analysis Program employed a photogrammetric method to characterize sediment grain size along 10 drift cells throughout Puget Sound that have active feeder bluffs and are rich in high-value natural resources. Previously, grain size distributions were obtained using a laborious and time consuming sieve analysis technique, which requires the collection of sediment samples for lab analysis. The sieve technique cannot incorporate coarse gravel and cobbles, which are a significant constituent of Puget Sound beaches. By employing Daniel Buscombe’s digital grain-size analysis algorithm on photos taken using a “Cobble Cam” technique, we were able to perform in-situ grain size characterization of sediments. Photos of sediment were taken along cross-shore beach profiles to enable both cross-shore and longshore comparisons of grain size distributions. At each profile, sediment grain size was obtained at increments of 0.5m elevation, extending from the backshore to the shoreline, with the locations of samples recorded using real-time kinematic GPS equipment

Coastal Zone Mapping along the Elwha Drift Cell, Central Strait of Juan de Fuca

During the summer of 2015, the Washington State Department of Ecology Coastal Monitoring & Analysis Program (CMAP) conducted two surveys to map the beaches, bluffs, and nearshore region of the Elwha Bluffs and Ediz Hook coastline in the central Strait of Juan de Fuca near Port Angeles, Washington. This work, funded by the US Army Corps of Engineers, provides the ability to assess shoreline change within one season over a 4-month timespan. High-resolution topographic and bathymetric data was collected using boat-based lidar and dual-head multibeam sonars aboard the R/V George Davidson, with additional topographic data collected by foot using GPS on backpacks to fill in shadows from the lidar and walk cross-shore transects. By employing these methods, seamless coastal zone mapping from bluff top to over 10-m water depth was achieved. These data sets represent the first ever drift-cell scale comprehensive and detailed mapping of both coastal bluffs and the nearshore. Together, the surveys enable assessment of bluff sediment supply to beaches and the dispersal of sediment through the nearshore zone. While the interval between surveys was relatively short, significant human-induced and natural erosion of the Elwha bluffs was observed between June and October. In particular, the massive reshaping of the bluff face and uplands at the Port Angeles landfill (still in progress) provides snapshots of prior conditions of the bluff, beach, and associated seawall along a portion of the project site. These data also provide an essential baseline for assessment of anticipated increased littoral sediment supply resulting from the removal of the Elwha dams and can be used in conjunction with previous nearshore and beach profile data collected by the US Geological Survey and CMAP before and after dam removal. The change analysis to date suggests sediment from the delta is beginning to make an imprint in the nearshore fronting the Elwha bluffs, with sand blanketing lower intertidal cobbles and initiating the choking of kelp beds

Baseline mapping of beaches and bluffs with boat-based lidar

In 2015, the Washington State Department of Ecology Coastal Monitoring & Analysis Program (CMAP) collected high-resolution baseline beach and bluff topographic data using boat-based lidar along nearly two dozen drift cells spanning \u3e200 km of Puget Sound shoreline. The lidar data was complemented by the concurrent collection of shoreline photographs, ground-based GPS surveys, and beach sediment grain-size. The drift cells were selected based on a rigorous and systematic geospatial analysis of bluff-backed beaches for their potential for significant bluff sediment supply to intact shorelines identified as having a relative abundance of habitat for forage fish, eelgrass, herring, shellfish, and geoduck, as well as having previous investments in beach restoration projects. As such, the surveyed drift cells are top candidates for implementing drift cell-scale protection and restoration strategies. The data set provides the opportunity to inventory and characterize the shoreline landscape that affects nearshore ecosystem services such as feeder bluff activity, beach slope and width, the position, length, and elevation of armoring relative to the backshore, and quantities of large woody debris and overhanging riparian vegetation. Compared to airborne lidar, boat-based lidar provides a more advantageous point of view of the bluff face, resulting in much higher resolution data which is needed to gain insight into bluff failure and erosion mechanisms and corresponding sediment transport processes. In addition, the near-horizontal look angle of the laser enables high density data of vertically oriented features such as bluffs and shoreline armoring, and successfully collects data under overhanging vegetation and overwater structures. Repeat surveys in the future would enable change analyses for quantifying bluff sediment supply, changes in marine riparian vegetation, and a better understanding of the linkages between physical and ecological processes