Coastal erosion as a sediment source – implications for shoreline management

Puget Sound Feeder Bluffs: Coastal erosion as a sediment source and its implications for shoreline management Shipman et al 2014 .
See the PDF: pugetsoundhardening1406016

feederbluffreport

This report examines the role of eroding bluffs as a source of sediment for Puget Sound beaches and includes a review of related geology and coastal processes. It summarizes recent mapping of feeder bluffs and examines ways in which this information can be used to improve shoreline management.

This report is one part of a larger project on Puget Sound feeder bluffs that also includes maps and a series of web pages that cover much of the material in this report. The project was funded by EPA and the WA Department of Fish and Wildlife. Hugh Shipman and colleagues  published this  important report on feeder bluffs processes and management. Coastal Watershed Index of Port Angeles has been working on the complex and critical topic of feeder bluff management for over a decade. One of their biggest challenges is imparting the critical and unique elements of feeder bluff function and management (including the reality that there are no ‘soft armoring’ techniques appropriate for this land form ). This report provides scientific and management focus specifically to feeder bluffs of the Salish Sea- it’s long overdue.

 

feederbluffmaps

 

Part 2 is of the maps of feeder bluffs of Puget sound:

 

 

 

Accessed Nov 4, 2014 at :
https://fortress.wa.gov/ecy/publications/SummaryPages
Maps:
https://fortress.wa.gov/ecy/publications/publications/1406016part2.pdf/1406016.html.

See More on Feeder Bluff mapping:

 

 

 

 

 

Forage Fish in Metchosin

All articles and posts on the MetchosinCoastal website under the title Forage Fish may be found here:

In 2008 and in  2013, Ramona de Graaf, a biologist with the Public Education Program at the Bamfield Marine Station gave presentations on Forage Fish on our beaches  and the need to Document their occurrence. In 2008 on the Saturday after the presentation, we rejoined for a walk and a session on the process involved in sampling for Forage Fish on Taylor Beach. Ramona is also the principal and founding marine scientist of Emerald Sea Research and Consulting.

Our thanks from the Blue-Green Spaces committee to Ramona and Wen-Ling for this informative session on the importance of monitoring and preserving forage fish habitat.

See also the post: Overhanging Vegetation, Invertebrates and Forage fish

See also Forage Fish of Metchosin and Beyond by Moralea Milne with an article by Briony Penn : The herring, the Chinook and the Orca…At the Brink.  Moralea also documents a second training session by Ramona on Taylor Beach in March of 2009. Inclued is an article she wrote for the January Issue of The Metchosin Muse.

Throughout the Strait of Georgia, fish stocks have dramatically declined. Lingcod, rockfish and some Pacific salmon species are only some of the major commercial fish species in decline. Seabird populations throughout British Columbia and Washington State are also decreasing. As well, marine species such as the southern resident killer whale, dependent on salmon runs, have been listed as endangered. Many of these species depend on bait or ?forage? fishes as prey. Spawning habitat of forage fishes is located in nearshore marine environments, an environment heavily impacted by human development.

            Documenting and protecting forage fish spawning habitats must be a priority for the Metchosin Coastline.

There is little information on the current extent and health of the spawning habitats of herring and no information on the spawning habitat of surf smelt and Pacific sand lance. Surf smelt and sand lance spawn in gravel/sand beach habitats in the upper one third of the intertidal zone (Figure 1). Current spawning habitats of surf smelt and sand lance have been documented throughout the US coasts of the Juan de Fuca Strait, San Juan Islands, and Puget Sound (Penttila 2000, 2001). In Canada, eelgrass beds are protected as critical fish habitat under Fisheries and Oceans Canada ?no-net? loss policy (Federal Fisheries Act). Protecting forage fish spawning and rearing habitats will have positive benefits by protecting a vital food source for numerous marine predators. Fisheries and Oceans Canada recognizes the need to obtain information on the habitat requirements of forage fishes in Coastal areas.

intertidalzone

Intertidal zone spawning locations.
WHAT ARE WE CONCERNED ABOUT WITH METCHOSIN’S BEACHES?Diversion of sediment-bearing streams through culverts, and the backshore and intertidal placement of seawalls, outfall pipes and riprap armouring interrupt natural coastal processes (such as erosion) that supply terrestrially-borne gravel sediments to beaches crucial to spawning surf smelt and Pacific sand lance. Seawalls are physical barriers that block the seaward transport of eroding gravels from feeder bluffs. Impediment of the long-shore transport of sediments by groins, outflow pipes, piers, boat ramps and docks have all contributed to the sediment-starved state of some beach faces. In general, the placement of seawalls and riprap armouring in the backshore and in the intertidal continues the process of sediment deprivation due to the action of wave scouring. Wave scouring can result in the loss of fine sands and gravels (appropriate for spawning) and the dominance of coarser (larger) gravels and cobble beaches inappropriate for use as spawning gravels for both surf smelt and Pacific sand lance. Seawalls such as those on Albert Head and Tower Point are often placed in the backshore, supralittoral and high intertidal zones (the uppermost portion of the high tide range) which can result in the loss of spawning habitat area, a decrease in beach elevation, an increase in beach slope, interruption of the sediment-transport drift cell, and the loss of sediment retaining logs. Not only are these ?hard? approaches to storm protection negatively impacting forage fish populations, but they can fail to deliver the protection intended. Around the world and locally, there are growing incidences of seawalls and other armouring failing to protect land owners. Modern engineering approaches, or ?soft? approaches work with coastal processes to provide safety for human populations and industries as well as maintaining marine ecological functions. While this report will not address this topic in detail, several informative websites and consultants include http://www.greenshores.ca, http://www.coastalgeo.com, http://www.herrarainc.ca and http:// www.sanjuans.org.
The presence of overhanging vegetation in marine riparian zones is important for the ecological function of nearshore marine habitats (Levings and Jamieson 2001; Brennan and Culverwell 2004) including having a positive effect on surf smelt spawn survival (Penttila 2001). The loss of overhanging vegetation (due to shoreline hardening measures) in the marine riparian zone has several ecological implications not only for marine fish and invertebrates, but the loss of shade cover increases the mortality of incubating surf smelt eggs (Penttila 2001, Rice 2006). Summer beach sediment temperatures are moderated by overhanging vegetation. Surf smelt eggs are typically anchored to surface gravels but are also buried between interstitial spaces within sediments layers (Penttila 2001). Surf smelt eggs deposited in summer months likely encounter high mortalities on the surface but eggs buried deeper in spawning substrates can avoid extreme surface temperatures and drying resulting in an increased survival rate (Penttila 2001). The loss of shading, however, increases thermal stress and desiccation to incubating eggs as temperatures within the sediments rise resulting in increased mortality of even buried eggs (Penttila 2001, Rice 2006). Vegetation buffers the drying effect of winds, and where beaches have lost riparian zones, eggs can also suffer a higher mortality than ?natural? due to wind-induced desiccation effects.
In Washington State, sand lance, surf smelt and other forage fish species such as anchovy are protected due to their importance to upper trophic levels of the food chain to support commercial fisheries (such as salmon, rockfish, ling god) and for ecosystem function (as advocated in WDFW principles of ecosystem management).
In general, surf smelt and Pacific sand lance depend on healthy nearshore and beach habitat, and they are vulnerable to impacts from shoreline development. Beaches with natural erosion processes supplying appropriate sized gravels and extant riparian zones are an optimal state for spawning surf smelt and sand lance. Winter spawning stocks of surf smelt may avoid desiccation stress and may have evolved to exploit beaches lacking overhanging vegetation (D. Penttila, pers. comm. 2007). Of primary importance for spawning is the mixture of gravels with a sand base. Cobbling beaches for heavy equipment operation, bulkheads, seawalls, outflow pipes and structures impeding sediment-transport drift cells are threats to maintaining these crucial spawning beaches.
The content of this report summarizes the data acquired from July 2006 to June 2007 (with mention of spawning results to September 07).The above was ADAPTED FROM RAMONA de GRAAF’S reference materials and the Forage Fish Report The photos above come from the Power Point presentation of Emerald Sea Research and Consulting. FORAGE FISH REPORT see www.birdsonthebay.ca The Boundary Bay intertidal forage fish spawning habitat report. Please contact Ramona and Wen-Ling of Forage Fish Matter! at emeraldsearesearch(use the at sign)hotmail.com or rdegraaf(use the at sign)bms.bc.ca for more information, talks or training!

 

Ramona has also supplied the following manual available here as a .pdf file:SURF SMELT AND PACIFIC SAND LANCE INTERTIDAL SPAWNING HABITAT ASSESSMENT
This manual is to guide surveys after training is provided by a biologist experienced in
monitoring for beach spawning forage fish (see page 6 for contact information). Sampling for
surf smelt and Pacific sand lance eggs consists of: Site selection (Section 1); obtaining a bulk
sample of mixed sand and gravel from the upper intertidal region of an appropriate beach
(Section 2); condensing the bulk sample to a manageable volume (Section 3); and examining
the condensed sample under a dissecting microscope to determine the presence or absence
of eggs (Section 4). Sections 1 -3 are supplied in this field guide as are field data codes and
data sheet. Pages 2 – 6 of this document can be laminated for use in the field.
Technical Report 2006-05
Nearshore Birds in Puget Sound Joseph B. Buchanan
Washington Department of Fish and Wildlife
Protecting Nearshore Habitat and Functions in Puget Sound
Technical Report 2006-06 Kurtl. Fresh, Noaa
Juvenile Pacific Salmon and the Nearshore Ecosystem in Puget Sound

Hardening of the Shorelines: Principles

The following is from :
Shorelines Modification , by the State of Washington Dept of Ecology

(ii) Principles. Shorelines are by nature unstable, although in varying degrees. Erosion and accretion are natural processes that provide ecological functions and thereby contribute to sustaining the natural resource and ecology of the shoreline. Human use of the shoreline has typically led to hardening of the shoreline for various reasons including reduction of erosion or providing useful space at the shore or providing access to docks and piers. The impacts of hardening any one property may be minimal but cumulatively the impact of this shoreline modification is significant.

Shoreline hardening typically results in adverse impacts to shoreline ecological functions such as:

  • Beach starvation. Sediment supply to nearby beaches is cut off, leading to “starvation” of the beaches for the gravel, sand, and other fine-grained materials that typically constitute a beach.
  • Habitat degradation. Vegetation that shades the upper beach or bank is eliminated, thus degrading the value of the shoreline for many ecological functions, including spawning habitat for salmonids and forage fish.
  • Sediment impoundment. As a result of shoreline hardening, the sources of sediment on beaches (eroding “feeder” bluffs) are progressively lost and longshore transport is diminished. This leads to lowering of down-drift beaches, the narrowing of the high tide beach, and the coarsening of beach sediment. As beaches become more coarse, less prey for juvenile fish is produced. Sediment starvation may lead to accelerated erosion in down-drift areas.
  • Exacerbation of erosion. The hard face of shoreline armoring, particularly concrete bulkheads, reflects wave energy back onto the beach, exacerbating erosion.
  • Ground water impacts. Erosion control structures often raise the water table on the landward side, which leads to higher pore pressures in the beach itself. In some cases, this may lead to accelerated erosion of sand-sized material from the beach.
  • Hydraulic impacts. Shoreline armoring generally increases the reflectivity of the shoreline and redirects wave energy back onto the beach. This leads to scouring and lowering of the beach, to coarsening of the beach, and to ultimate failure of the structure.
  • Loss of shoreline vegetation. Vegetation provides important “softer” erosion control functions. Vegetation is also critical in maintaining ecological functions.
  • Loss of large woody debris. Changed hydraulic regimes and the loss of the high tide beach, along with the prevention of natural erosion of vegetated shorelines, lead to the loss of beached organic material. This material can increase biological diversity, can serve as a stabilizing influence on natural shorelines, and is habitat for many aquatic-based organisms, which are, in turn, important prey for larger organisms.
  • Restriction of channel movement and creation of side channels. Hardened shorelines along rivers slow the movement of channels, which, in turn, prevents the input of larger woody debris, gravels for spawning, and the creation of side channels important for juvenile salmon rearing, and can result in increased floods and scour.

Additionally, hard structures, especially vertical walls, often create conditions that lead to failure of the structure. In time, the substrate of the beach coarsens and scours down to bedrock or a hard clay. The footings of bulkheads are exposed, leading to undermining and failure. This process is exacerbated when the original cause of the erosion and “need” for the bulkhead was from upland water drainage problems. Failed bulkheads and walls adversely impact beach aesthetics, may be a safety or navigational hazard, and may adversely impact shoreline ecological functions.

Hard” structural stabilization measures refer to those with solid, hard surfaces, such as concrete bulkheads, while “soft” structural measures rely on less rigid materials, such as biotechnical vegetation measures or beach enhancement. There is a range of measures varying from soft to hard that include:

  • Vegetation enhancement;
  • Upland drainage control;
  • Biotechnical measures;
  • Beach enhancement;
  • Anchor trees;
  • Gravel placement;
  • Rock revetments;
  • Gabions;
  • Concrete groins;
  • Retaining walls and bluff walls;
  • Bulkheads; and
  • Seawalls.

Generally, the harder the construction measure, the greater the impact on shoreline processes, including sediment transport, geomorphology, and biological functions.