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Bluff Recession in the Elwha and Dungeness Littoral Cells, Washington, USA

Authors:
  • Washington Department of Ecology

Abstract and Figures

The spatial distribution and temporal variability of retreat rates of coastal bluffs composed of unconsolidated glacial deposits are of interest to landowners who occupy bluff-top properties as well as coastal resource managers who are responsible for protecting marine habitats such as forage fish spawning beaches that are dependent on bluff-derived sediments. Assessment of bluff retreat and associated sediment volumes contributed to the nearshore over time is the first step toward development of a coastal sediment budget for bluff-backed beaches using data sources including aerial photography (1939, 2001), GPS-based beach profile data (2010–2013), and airborne LiDAR (2001, 2012). These data are analyzed in context to determine alongshore rates of bluff retreat and associated volume change for the Elwha and Dungeness littoral cells in Clallam County, WA. Recession rates from 2001 to 2012 range from 0 to 1.88 m/yr in both drift cells, with mean values of 0.26 ± 0.23 m/yr (N = 152) in Elwha and 0.36 ± 0.24 m/yr (N = 433) in Dungeness. Armored sections show bluff recession rates reduced by 50 percent in Elwha and 80 percent in Dungeness, relative to their respective unarmored sections. Dungeness bluffs produce twice as much sediment per alongshore distance as do the Elwha bluffs (average, 7.5 m 3 /m/yr vs. 4.1 m 3 /m/ yr, respectively). Historical bluff recession rates (1939– 2001) were comparable to those from 2001–2012. Rates derived from short timescales should not be used directly for predicting decadal-scale bluff recession rates for management purposes, as they tend to represent short-term localized events rather than long-term sustained bluff retreat.
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Bluff Recession in the Elwha and Dungeness Littoral
Cells, Washington, USA
DAVID S. PARKS
1
Washington State Department of Natural Resources, 311 McCarver Road,
Port Angeles, WA 98362
Key Terms: Environmental Geology, Land-Use Plan-
ning, Erosion, Landslides
ABSTRACT
The spatial distribution and temporal variability of
retreat rates of coastal bluffs composed of unconsolidated
glacial deposits are of interest to landowners who occupy
bluff-top properties as well as coastal resource managers
who are responsible for protecting marine habitats such
as forage fish spawning beaches that are dependent on
bluff-derived sediments. Assessment of bluff retreat and
associated sediment volumes contributed to the nearshore
over time is the first step toward development of a coastal
sediment budget for bluff-backed beaches using data
sources including aerial photography (1939, 2001), GPS-
based beach profile data (2010–2013), and airborne
LiDAR (2001, 2012). These data are analyzed in context
to determine alongshore rates of bluff retreat and
associated volume change for the Elwha and Dungeness
littoral cells in Clallam County, WA. Recession rates
from 2001 to 2012 range from 0 to 1.88 m/yr in both drift
cells, with mean values of 0.26 ±0.23 m/yr (N =152) in
Elwha and 0.36 ±0.24 m/yr (N =433) in Dungeness.
Armored sections show bluff recession rates reduced by
50 percent in Elwha and 80 percent in Dungeness, relative
to their respective unarmored sections. Dungeness bluffs
produce twice as much sediment per alongshore distance
as do the Elwha bluffs(average, 7.5 m
3
/m/yr vs. 4.1 m
3
/m/
yr, respectively). Historical bluff recession rates (1939–
2001) were comparable to those from 2001–2012. Rates
derived from short timescales should not be used directly
for predicting decadal-scale bluff recession rates for
management purposes, as they tend to represent short-
term localized events rather than long-term sustained
bluff retreat.
INTRODUCTION
Coastal bluffs are a dominant geomorphic feature
of the shorelines of the Strait of Juan de Fuca,
Washington State, USA, and are the primary source
of sediment contributed to mixed sand and gravel
beaches in the region (Schwartz et al., 1987;
Shipman, 2004; Finlayson, 2006; and Johannessen
and MacLennan, 2007). The spatial and temporal
distribution of bluff recession from wave-, wind-,
precipitation-, and groundwater-induced erosion is
poorly understood and documented for the southern
shore of the Strait of Juan de Fuca and has led to
underestimating the potential hazards to infrastruc-
ture (e.g., roads, houses) posed by eroding bluffs
over time (Figures 1 and 2). Efforts to protect
infrastructure and limit the rates of bluff erosion
by constructing shoreline revetments have historical-
ly ignored the physical and ecological effects of
sediment starvation of beaches caused by shoreline
hardening (Shipman et al., 2010). The disruption of
sediment movement from bluffs to beaches has
caused the loss of suitable habitats for critical marine
species, including forage fish and juvenile salmonids
(Rice, 2006; Shipman et al., 2010; Shaffer et al., 2012;
and Parks et al., 2013). The importance of under-
standing the long-term littoral sediment budget has
been underscored by the recent removal of two dams
on the Elwha River and the subsequent introduction
of approximately 6.4 310
6
m
3
of sediment into the
nearshore environment within the first 2 years
(between September 2011 and September 2013) (East
et al., 2014; Gelfenbaum et al., in review; and
Warrick et al., in review).
Relatively few studies of coastal bluff recession
have been completed for the shoreline areas of the
Strait of Juan de Fuca, and the studies that have been
completed have used a variety of methods, leading to
difficulty in comparing results. In the Elwha littoral
cell (herein referred to as ‘‘drift cell’’), the U.S. Army
Corps of Engineers (USACE) completed an evalua-
tion of bluff recession rates and sediment volume
supply to the nearshore environment as part of an
environmental assessment for a shoreline armoring
and beach nourishment project on Ediz Hook in Port
Angeles (USACE, 1971). Using Government Land
Office and National Geodetic Survey shoreline maps,
the USACE estimated a gradual reduction in bluff
recession rates from 1.5 m/yr (1850–1885) to 1.3 m/yr
1
Corresponding author email: david.parks@dnr.wa.gov.
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 129
(1885–1926), decreasing to 1.1 m/yr (1926–1948) and
then to 0.2 m/yr (1948–1970). Each successive
reduction in bluff recession rates since 1930 has been
attributed to construction and maintenance of a
multitude of shoreline armoring projects at the base
of the Elwha bluffs (USACE, 1971).
The USACE (1971) study also shows a reduction in
sediment volumes provided by the Elwha bluffs over
Figure 1. (A) Homes threatened by receding bluffs, Dungeness drift cell. (B) Seawall installed at bluff toe to protect Port Angeles City
Landfill from bluff retreat, Elwha drift cell.
Parks
130 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
time. Prior to the construction of the Elwha Dam in
1911, the estimated sediment supply from the bluffs
was 2.22 310
5
m
3
/yr. After construction of the Elwha
Dam and prior to construction of shoreline armoring
along the Elwha bluffs in 1929, the estimated
sediment supply from the bluffs was nearly the same,
measuring 2.06 310
5
m
3
/yr. Between 1929 and 1961,
when substantial shoreline armoring along the bluffs
was installed and maintained, the bluff sediment
supply decreased to 0.73 310
5
m
3
/yr. Following the
completion of a major shoreline armoring project
along the bluffs in 1961, bluff sediment supply was
estimated to have further declined to 0.31 310
5
m
3
/
yr. The reduction of bluff-supplied sediment over this
entire time period, 1.91 310
5
m
3
/yr, represents an 85
percent reduction in the coastal sediment supply to
Ediz Hook (Galster, 1989), which is essentially
equivalent to the pre-dam fluvial sediment supply
estimated by Randle et al. (1996).
Bluff erosion rates to the east of the Dungeness
drift cell along the Strait of Juan de Fuca were
evaluated through land-parcel surveys by Keuler
(1988). Bluff recession rates of up to 0.30 m/yr and
sediment production rates of 1–5 m
3
/m/yr were
observed in areas exposed to wave attack associated
with long fetches. On the west side of Whidbey Island,
at the eastern limit of the Strait of Juan de Fuca,
Rogers et al. (2012) determined long-term bluff
erosion rates of 0–0.08 m/yr using cosmogenic
10
Be
concentrations in lag boulders to date shoreline
positions over time scales of 10
3
–10
4
years.
In this study, estimates of short- and long-term
bluff recession rates and associated sediment volumes
contributed to the Elwha and Dungeness drift cells
along the Central Strait of Juan de Fuca between
1939 and 2012 are derived from historical aerial
photography, GPS beach profiles, and airborne
LiDAR, and the relative contribution of bluff-derived
sediment supply to the nearshore, in the context of a
coastal sediment budget recently rejuvenated by the
removal of two dams on the Elwha River, is
presented.
STUDY AREA
The study area is located on the southern shore of
the Central Strait of Juan de Fuca near the city of
Port Angeles, WA (Figure 2). The study area is
divided into two distinct shoreline segments that
encompass separate but adjacent littoral cells with
bluff-backed beaches: the Elwha bluffs extend along
the central portion of the Elwha drift cell, and the
Dungeness bluffs extend along the western portion of
the Dungeness drift cell (Figure 3). Each drift cell
contains an updrift segment of eroding coastal bluffs
to the west that supply sediment via longshore littoral
Figure 2. Map of the study area showing direction of net alongshore sediment transport within the Elwha and Dungeness drift cells in
Clallam County, WA.
Coastal Bluff Recession
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 131
transport to long spits at the down-drift end to the
east.
The Elwha bluff segment is 4.9 km long and
supplies sediment to Ediz Hook. The Dungeness bluff
segment is 13.6 km long and supplies sediment to
Dungeness Spit. A fundamental difference between
the two drift cells is that the Elwha River discharges
into the Strait of Juan de Fuca updrift of the Elwha
bluffs, while the Dungeness River empties into the
Strait of Juan de Fuca on the lee side of Dungeness
Figure 3. (A) Photograph of the Dungeness bluffs looking west from Dungeness Spit. (B) Photograph of the Elwha bluffs west from Ediz
Hook. Note the armoring placed mid-beach in front of the bluffs in photograph B.
Parks
132 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
Spit (Figure 2). Therefore, the Elwha drift cell is
composed of both river- and bluff-derived sediments,
while the Dungeness drift cell is composed of only
bluff-derived sediments.
The Strait of Juan de Fuca is a wind-dominated
marine system that exhibits net easterly longshore
sediment transport within the intertidal zone of the
study area (Galster and Schwartz, 1989; Schwartz et
al., 1989; Warrick et al., 2009; and Miller et al., 2011).
Winds in the Central Strait of Juan de Fuca are
dominantly west and northwesterly, with a minor
component of north and northeasterly winds (Miller
et al., 2011). Therefore, both the Elwha and Dunge-
ness drift cells exhibit net easterly littoral sediment
transport (USACE, 1971; Galster and Schwartz,
1989; and Schwartz et al., 1989).
The wave climate of the Central Strait of Juan de
Fuca is similarly dominated by west to northwest
wind waves and west to northwest swells from the
Pacific Ocean. Maximum wave heights within the
study area range up to 3 m, whereas average heights
are 0.5 m (USACE, 1971; Gelfenbaum et al., 2009;
Warrick et al., 2009; and Miller et al., 2011).
Gelfenbaum et al. (2009) have modeled the distribu-
tion of significant wave heights within the Central
Strait of Juan de Fuca, and given a 2-m swell at the
entrance to the Strait of Juan de Fuca, nearshore
wave heights of 1 m are shown throughout the study
area, but with significant alongshore variability in
wave height due to wave focusing or sheltering and in
wave direction due to refraction.
Tides within the Strait of Juan de Fuca are mixed-
diurnal, with two high and low tides per day. Tidal
elevations range between 21.0 m and +3.7 m in
elevation (NAVD 88) (Zilkoski et al., 1992; NOAA,
2013).
A precipitation gradient exists from west to east
within the study area as the result of a rain-shadow
effect of the Olympic Mountains. Average annual
precipitation (1971–2000) in the Elwha drift cell is
660 mm vs. 406 mm in the Dungeness drift cell
(Drost, 1986; NCDC, 2014). Maximum rainfall
intensities within the Elwha drift cell are 117 mm/hr
vs. 71 mm/hr in the Dungeness (Drost, 1986; NCDC,
2014). Precipitation occurs primarily as rain, with the
wettest months between October and April and a
seasonal dry period between May and September.
Freezing temperatures occur within the study area
between October and May, and snowfall intermit-
tently occurs in the period between November and
April.
The surficial geology of the study area is domi-
nantly composed of Pleistocene continental glacial
deposits overlying pre-Fraser non-glacial sediments
associated with an Elwha River source (Schasse et al.,
2000; Polenz et al., 2004) and Eocene marine
sedimentary rocks (Schasse et al., 2000; Schasse and
Polenz, 2002; Schasse, 2003; and Polenz et al., 2004).
Pleistocene glacial deposits occurring within the study
area include recessional outwash, glaciomarine drift,
and glacial till.
Groundwater recharge occurs along the Olympic
Mountains and discharges into the Strait of Juan de
Fuca. Local groundwater recharge occurs within low-
elevation glacial landforms adjacent to the coastal
bluffs and discharges at varying elevations on the
bluffs controlled by local aquitards (i.e., beds of low-
permeability materials composed of dense silt, clay,
and till) (Drost, 1986; Jones, 1996).
The shoreline within the study area exhibits steeply
sloping to vertical and overhanging coastal bluffs up
to 80 m high created by changes in relative sea level
from post-glacial rebound following Cordilleran
glacial retreat; erosion of the shoreline in the study
area began around 5,400 years before the present time
(Downing, 1983; Dethier et al., 1995; Booth et al.,
2003; Schasse, 2003; Mosher and Hewitt, 2004; and
Polenz et al., 2004).
Bluff recession within the study area is dominated
by shallow landsliding in the form of topples, debris
avalanches, flows, and slides (Varnes, 1978). Other
types of gravitational failures are also present,
including stress release fracturing (Bradley, 1963),
cantilever, and Culmann-type (near-vertical planar)
failures (Carson and Kirkby, 1972). These types of
shallow mass wasting processes are common in sea
cliffs composed of weakly lithified sediments (Hamp-
ton, 2002). Aeolian erosion during dry periods (in the
form of ravel) is also observed. Aerial-, boat-, and
ground-based surveys of the study area have deter-
mined the absence of deep-seated (Varnes, 1978)
landslides consistent with existing geologic mapping
(Schasse et al., 2000; Schasse and Polenz, 2002;
Schasse, 2003; and Polenz et al., 2004). Processes
driving shallow landsliding include over-steepening
and subsequent failure of bluffs from wave-induced
erosion at the bluff-base and the development of high
pore-water pressures within hillslopes during storms.
Land use above the bluffs varies throughout the
study area from dense urban development in the
Elwha drift cell within the City of Port Angeles to
native second-growth forest within the Dungeness
drift cell. Vegetation within the study area ranges
from dense stands of mature second- and third-
growth Douglas fir forest to open grass associated
with urban lawn-scapes.
The sediment budget of the Elwha drift cell has
substantially declined as a result of human-induced
changes. The construction of coastal revetments
began in the Elwha drift cell shortly after the
Coastal Bluff Recession
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 133
construction of two dams on the Elwha River in the
early 20th century (Galster, 1989). In 1929, a coastal
revetment was installed between Dry Creek and Ediz
Hook to protect an industrial waterline that supplied
water from the Elwha River to paper mills on Ediz
Hook. Within 6 years of the placement of coastal
defense works, Ediz Hook began to erode as a result of
the reduction in sediment supply from bluffs (Galster,
1989). Galster (1989) estimated that in the Elwha drift
cell, 15 percent of the sediment supplying Ediz Hook
originated from the Elwha River, and 85 percent was
supplied from coastal bluff erosion prior to construc-
tion of Elwha River Dams and coastal revetments.
Galster (1989) estimated that coastal armoring in the
Elwha drift cell resulted in an 89 percent reduction of
sediment volume supplied to Ediz Hook. In 1975, the
USACE and the City of Port Angeles armored the
shoreline of Ediz Hook and began a program of beach
nourishment that continues to the current time. In
2005, the City of Port Angeles constructed a 122 m–
long concrete, steel, and rock seawall at the Port
Angeles Landfill. Currently, 68 percent of the Elwha
bluffs are armored with rip-rap or constructed
seawalls. In contrast, less than 1 percent of the length
of the Dungeness bluffs is armored.
In 2012, the Elwha Dam on the Elwha River was
completely removed, and, as of 2014, the Glines
Canyon Dam has also been completely removed,
resulting in the delivery of 6.4 310
6
m
3
of
predominantly fine sediment to the nearshore of the
Elwha littoral cell within the first 2 years since dam
removal began in September 2011 (East et al., 2014;
Gelfenbaum et al., in review; and Warrick et al., in
review). This sediment volume represents approxi-
mately 30 percent of the total sediment stored in both
reservoirs. It is estimated that within 7–10 years
following the complete removal of both Elwha River
Dams, the long-term annual sediment contribution
from the Elwha River to the nearshore will be
approximately 2.5 310
5
m
3
/yr (Gilbert and Link,
1995; Bountry et al., 2010).
Understanding the relative contribution of bluff
erosion to the overall sediment budget of the Elwha
drift cell will help with efforts to manage the long-
term coastal environment once the reservoir sedi-
ments released by dam removal have been transport-
ed out of the fluvial network and into the Strait of
Juan de Fuca.
METHODS
Bluff-Face Change Mapping
Short- and long-term coastal bluff recession rates
for the Elwha and Dungeness drift cells were
determined by analyzing data from historical aerial
photographs and existing airborne LiDAR data. In
order to make comparisons of the bluffs between the
two data types, two-dimensional cross-shore transects
were established in each drift cell at 30-m intervals,
except where interrupted by coastal streams or
ravines (Figure 4). Transects extend across the beach
and up the bluff face, to at least the bluff crest, along
which retreat distances could be calculated. Bluff
retreat was measured between consecutive surveys at
the bluff crest for aerial photos and at selected
elevations across the bluff face for LiDAR data.
Long-Term Bluff Change
Bluff recession rates for 1939–2001 were deter-
mined by calculating the distance between bluff crest
positions on geo-referenced historical aerial photo-
graphs. Prior to analysis, aerial photographs were
scanned, geo-referenced, and imported into ArcGIS
v. 10.1 (ESRI, Redlands, CA), and bluff crest
positions were digitized for study segment areas
unobstructed by vegetation. Distances between the
1939 and 2001 bluff crest positions were measured at
each transect location.
Recession rates for 2001–2012 were determined
from the differences in horizontal position of selected
elevations on bluff-face profiles extracted from digital
elevation models (DEMs) available from recent
airborne LiDAR data sets using methods outlined
in Hapke (2004), Young and Ashford (2009) and
Young et al. (2009, 2010, 2011). For this analysis, we
used a 2001 bare earth DEM (2-m grid) from the
Puget Sound LiDAR Consortium (PSLC, 2001) that
covered the entire survey area, 2012 Clallam County
LiDAR (1-m grid; Yotter-Brown and Faux, 2012) for
the Dungeness drift cell, and 2012 LiDAR data (0.5-
m grid) from the U.S. Geological Survey (Woolpert,
2013) for the Elwha drift cell. DEMs were imported
into ArcGIS and evaluated using the 3D Analyst
toolset. At each transect location a two-dimensional
topographic profile from the mid-beach to the bluff
crest was extracted from each DEM. The net
horizontal distance between the two profiles was
measured at 6-m vertical intervals between the
bottom and top of the bluff face. The difference in
total cross-sectional area between the 2001 and 2012
topographic profiles was measured and multiplied by
a unit width to estimate a volume of sediment lost
between the two DEMs.
Statistical evaluation of the data for bluff recession
and sediment volume contributions from the airborne
LiDAR DEMs was performed using exploratory data
analysis methods (Schuenemeyer and Drew, 2011).
Bluff recession distance values were tested for spatial
Parks
134 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
Figure 4. Map showing bluff and beach transect locations for the Elwha bluffs (A) and Dungeness bluffs (B5west, C5east).
Coastal Bluff Recession
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 135
trend and normalized using a lognormal transforma-
tion. Summary statistics were then computed using
the de-trended values. Sources of error include
internal error in the LiDAR data acquisition and
processing technique as well as differences in grid size
of the LiDAR-derived DEMs.
Beach Profile Change Monitoring
To assess general trends in beach elevation change
(m/yr) and to estimate rates of sediment flux on the
beaches (m
3
/m/yr), two-dimensional, cross-shore to-
pographic beach profiles at 12 locations, eight along
the Dungeness bluffs and four along the Elwha bluffs,
were surveyed between 2010 and 2013 with a Pro-
Mark 800 and 200 Real-Time Kinematic Global
Positioning System (RTK-GPS). Elwha and Dunge-
ness drift cell beach profiles were collected in all
seasons. Profiles were oriented normal to the slope of
the beach, extending from the base of coastal bluffs to
the low water limit. Elevation measurements were
recorded along each transect at horizontal intervals of
approximately 1.5 m. RTK-GPS measurement accu-
racy ranged from 1 to 5 cm based on repeat
measurements of fixed control points across the study
area.
Sediment volume changes were calculated using the
upper 20 m of each profile, which was the extent of
overlap between all surveys. The elevation difference
between each pair of profiles was calculated every
0.5 m, with a linear interpolation between the original
1.5-m data point spacing. The difference values along
the entire transect were averaged to yield a single
value of average elevation change per transect. The
average elevation change was multiplied by the 20-m
length of the profile and an alongshore unit width of
1 m to yield a volume change per alongshore meter
(m
3
/m) for the 20 m of upland beach.
RESULTS
Bluff-Face Change
Long-Term Bluff Change
Observed rates of coastal bluff recession are highly
variable across both drift cells (Figures 5–7). Table 1
provides data results from sections of each drift cell
with unobstructed views of the bluff edge in aerial
photography from 1939 and 2001 and includes
identical shoreline reaches used for a comparison of
rates derived from airborne LiDAR from 2001 and
2012. The data show a recent decrease in mean
recession rates in the Elwha drift cell (20.22 m/yr)
and a slight increase in mean recession rates in recent
years in the Dungeness drift cell (+0.1 m/yr).
Table 2 provides data results that extend along
the full length of the bluffs in each drift cell. The
maximum observed rate of recession between 2001
and 2012 in both drift cells was 1.88 m/yr, associated
with housing development in the Dungeness drift cell
(Figure 1A) and erosional hotspots along the Port
Figure 5. Maximum observed bluff recession rates (m/yr) in the Dungeness drift cell for the time periods 1939–2001 (derived from aerial
photography) and 2001–2012 (derived from airborne LiDAR).
Parks
136 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
Figure 6. Maximum observed bluff recession rates (m/yr) in the Elwha drift cell for the time periods of 1939–2001 (derived from aerial
photography) and 2001–2012 (derived from airborne LiDAR).
Figure 7. Box plot of recession rates (m/yr) by drift cell and shoreline type (created in ABOXPLOT; Bikfalvi, 2012). The central line within
the box represents the sample median, while the circle represents the sample mean. The upper and lower limits of the box represent the 50th
percentile of the population and the whiskers the 75th percentile. Dots beyond the upper and lower whiskers represent outliers of
the population.
Coastal Bluff Recession
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 137
Angeles landfill revetment in the Elwha drift cell
(Figure 1B). The mean recession rate in the Dunge-
ness was 0.36 m/yr vs. 0.26 m/yr for the Elwha drift
cell (Table 2) for the 2001–2012 period.
In both drift cells, armored sections of bluffs
showed significantly lower rates of recession than
did unarmored sections: 80 percent less in the
Dungeness drift cell and 50 percent less in the Elwha
drift cell (Table 2 and Figure 7). Unarmored bluff
sections demonstrated very similar mean rates of
recession between drift cells: 0.37 m/yr for Dungeness
and 0.40 m/yr for Elwha (Table 2 and Figure 7).
Unarmored sections of bluffs directly down-drift and
adjacent to armored sections experienced the highest
rates of bluff recession in the Elwha drift cell (1.88 m/
yr) and higher than mean rates (1.0 m/yr) in the
Dungeness drift cell (Figure 7).
Sediment volumes eroded from bluffs in the Dunge-
ness drift cell were almost double those observed in the
Elwha drift cell per transect (Table 3 and Figures 8–
10). The mean sediment production rate in the
Dungeness drift cell was 25.4 m
3
per transect vs.
13.8 m
3
per transect in the Elwha drift cell. Rates of
sediment production from unarmored sections of
bluffs were similar between drift cells. Mean values
for sediment production from unarmored sections of
bluffs in the Dungeness drift cell were 25.8 m
3
per
transect vs. 22.0 m
3
per transect for the Elwha drift cell
(Table 3). Sediment production rates for armored
sections of bluffs were twice as high in the Elwha drift
cell (11.9 m
3
per transect) compared to the Dungeness
drift cell (5.8 m
3
per transect) (Table 3 and Figure 10).
At the drift cell scale, the Dungeness bluffs
produced approximately five times the volume of
sediment of the Elwha bluffs, on average (1.03 3
10
5
m
3
/yr vs. 2.0 310
4
m
3
/yr, respectively), on an
annual basis over the 2001–2012 period (Table 4).
When normalized for length, the Dungeness bluffs
contributed approximately 55 percent more sediment
than did the Elwha bluffs to the nearshore (7.5 m
3
/m/
yr vs. 4.1 m
3
/m/yr, respectively) on an annual basis
for the 2001–2012 period (Table 5).
Beach Sediment Volume Changes
Annual beach sediment volume changes as well as
the net 3-year change at the 12 transect locations
(eight along the Dungeness bluffs; four along the
Elwha bluffs) are shown in Figure 11 and Tables 6
and 7. With the exception of transect EB-1 (where the
effects of sediment supply from the Elwha River are
evident), the general trend in beach sediment volume
has been one of net loss over the 3-year period
occurring between 2010 and 2013.
In the Elwha drift cell, annual beach transect
elevation changes ranged from 20.72 (net loss) to
+1.19 m/yr (net gain) (mean 520.13 60.52 m/yr). The
greatest loss at all Elwha transects occurred during the
2010–2011 period. In the Dungeness drift cell, annual
beach transect elevation changes ranged from 21.05 m/
yr to +0.22 m/yr (mean 520.19 60.29 m/yr).
DISCUSSION
Bluff Recession Rates
Rates of bluff recession observed in this study in
the Elwha drift cell generally agree with rates
Table 1. Recession rates (m/yr) from aerial photography (1939–2001) and airborne LiDAR (2001–2012) for unobstructed bluff-edge reaches
of each drift cell.
Drift Cell Period
Minimum
(m/yr)
Mean
(m/yr)
Maximum
(m/yr)
Standard Deviation
(m/yr)
No. of
Transects Length (m)
Dungeness 1939–2001 0.0 0.40 1.00 0.20 181 5,639
2001–2012 0.1 0.50 0.90 0.17 181 5,639
Elwha 1939–2001 0.2 0.42 0.60 0.10 75 2,469
2001–2012 0.0 0.20 0.55 0.10 75 2,469
Table 2. Recession rates (m/yr) by drift cell and shoreline type, 2001–2012.
Drift Cell Shoreline Type
Minimum
(m/yr)
Mean
(m/yr)
Maximum
(m/yr)
Standard Deviation
(m/yr)
No. of
Transects Length (m)
Dungeness Unarmored 0.0 0.37 1.88 0.79 423 13,320
Armored 0.0 0.08 0.46 0.40 10 305
All 0.0 0.36 1.88 0.24 433 13,625
Elwha Unarmored 0.0 0.40 1.88 1.30 60 1,829
Armored 0.0 0.21 0.58 0.40 92 3,048
All 0.0 0.26 1.88 0.23 152 4,877
Parks
138 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
measured by the USACE (USACE, 1971) in the
Elwha drift cell in the decade between 1960 and1971,
but they are elevated over those observed by Keuler
(1988) in the Dungeness drift cell and are substan-
tially higher than the long-term rates observed by
Rogers et al. (2012) for Eastern Strait of Juan de Fuca
shorelines. Rates of bluff erosion documented in this
study are also consistent with rates observed along the
west coast of the United States exposed to open-ocean
wave climates (Collins and Sitar, 2008; Pettit et al.,
2014). Rates of bluff recession observed between 2001
and 2012 may represent higher-than-average erosion
rates due to high storm frequency and intensity
occurring during this period: two time intervals, the
winters of 2007 and 2009, represent two of the wettest
and windiest periods on record for this location
(NCDC, 2014). Additionally, the 2001–2011 period
experienced four high-tide events that exceeded the
50-year recurrence interval for extreme high water
levels in the Central Strait of Juan de Fuca (NOAA,
2013).
Bluff recession rates observed in the Dungeness and
Elwha drift cells in this study have immediate
application to land-use planning for residential and
commercial construction activities adjacent to the
coastal bluffs. Given a typical design life of a single
family home of 100 years, applying the observed
mean bluff recession rates (Table 1) provides a
minimum setback distance between a structure and
the edge of the bluff of 42 m in the Elwha drift cell
and of 40 m in the Dungeness drift cell, based on
mean long-term (1939–2001) recession rates. It should
be noted that these rates of observed bluff recession
fall closely in line with estimates of 0.47 m/yr
published for the Elwha drift cell by Polenz et al.
(2004) and likely represent the long-term post-glacial
average bluff recession rate for glacial deposits on the
south shore of the Central Strait of Juan de Fuca.
Extending past observed bluff recession rates into
the future is likely a simplistic and inaccurate method
to determine future bluff recession (Hapke and Plant,
2010). Probabilistic methods of predicting bluff
erosion (Lee et al., 2001; Walkden and Hall, 2005;
and Hapke and Plant, 2010) that accommodate
spatial and temporal variability could be applied to
the Dungeness and Elwha drift cells and would likely
be more accurate than using hindcast observations
of bluff recession to predict future erosion rates.
Table 3. Sediment volume contribution per transect (m
3
) by drift cell and shoreline type, 2001–2012.
Drift Cell Shoreline Type Minimum (m
3
) Mean (m
3
) Maximum (m
3
)
Standard
Deviation (m
3
) No. of Transects Length (m)
Dungeness Unarmored 0.0 25.8 163.3 24.3 423 13,320
Armored 0.0 5.8 9.6 3.8 10 305
All 0.0 25.4 124.8 31.7 433 13,625
Elwha Unarmored 0.0 22.0 143.6 30.1 60 1,829
Armored 0.0 11.9 41.2 7.9 92 3,048
All 0.0 13.8 159.9 35.9 152 4,877
Figure 8. Sediment volume (m
3
) per transect in the Dungeness drift cell (2001–2012).
Coastal Bluff Recession
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 139
Figure 9. Sediment volume (m
3
) per transect in the Elwha drift cell (2001–2012).
Figure 10. Box plot of sediment volume contributions (m
3
/transect) by drift cell and shoreline type (created in ABOXPLOT; Bikfalvi,
2012). The central line within the box represents the sample median, while the circle represents the sample mean. The upper and lower limits
of the box represent the 50th percentile of the population and the whiskers the 75th percentile. Dots beyond the upper and lower whiskers
represent outliers of the population.
Parks
140 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
However, the data necessary to employ these proce-
dures (e.g., wave and tidal height distributions along
the bluffs) are not currently available.
Sediment Volume Change
Annual sediment volume contributions within the
Elwha drift cell from this study (2.0 310
4
m
3
/yr;
Table 4) are consistent with the flux of 3.1 310
4
m
3
/
yr determined by USACE (1971). The calculated
length-normalized rate of 4.1 m
3
/m/yr for the Elwha
drift cell is substantially less (255 percent) than the
rate observed (7.5 m
3
/m/yr) for the Dungeness drift
cell, which is consistent with a previous study by
Keuler (1988) that measured sediment contribution
rates for the exposed areas of the Strait of Juan de
Fuca ranging between 6.0 and 12.0 m
3
/m/yr.
Bluff-supplied sediment volume estimates for the
Elwha drift cell from this study can help refine the
coastal sediment budget post–dam removal. Since
shore-protection works in the Elwha drift cell will
remain after the Elwha Dams have been removed, a
significant component of the Elwha drift cell sediment
budget will remain impaired after the sediment supply
from the Elwha River has been restored.
Randle et al. (1996) estimates that the pre-dam
fluvial sediment contribution to the Strait of Juan de
Fuca was about 1.9 310
5
m
3
/yr. In the Elwha drift
cell, the current upper estimate of annual sediment
volume contribution to the nearshore from bluff
erosion is approximately 2.0 310
4
m
3
/yr–4.9 3
10
4
m
3
/yr (Table 4), or about 11–26 percent of the
pre-dam annual sediment contribution from the
Elwha River. The current annual sediment volume
contribution from bluff erosion in the Elwha drift cell
represents a 90 percent reduction from the 1911 pre-
armoring estimate (2.2 310
5
m
3
/yr; USACE, 1971)
but is roughly approximate to the 1960 post-armoring
estimate (3.1 310
4
m
3
/yr; Galster, 1989).
Comparing the sediment production rates between
the Dungeness and Elwha bluffs demonstrates the
level of impairment within the Elwha drift cell. When
normalized for drift cell length, the Elwha bluffs
produce 56 percent less sediment volume than do the
Dungeness bluffs on an annual basis. Comparing the
measured rates of sediment production from bluffs
(Table 5) versus sediment volume change in beach
transects (Tables 6 and 7 and Figure 11) demon-
strates the imbalance in the sediment supply relative
to available sediment transport. In most years, the
amount of available sediment volume contributed
from bluffs to the beach is substantially less than the
average rate of sediment loss, leading to beach
lowering and resulting in accelerated bluff erosion.
Management Implications
Bluff recession rates were shown to vary depending
on the time of measurement and length of time
observed. It is not appropriate to extrapolate short-
term measurements into long-term rates, especially if
the length of measurement is less than the time span
of the rate being reported (e.g., producing an annual
rate from ,1 year of observation). For instance, a
measurement taken over a month when there was a
large bluff failure could result in large overestimates
of bluff recession on an annual basis if there was no
further change for the remainder of the year.
Moreover, using the maximum measured recession
distance to calculate an annual recession rate will
result in an even-greater overestimate and could give
a false impression of how much the bluff is actually
retreating. The maximum recession distance is mea-
sured for a specific point along the bluff and may not
represent the trends observed over the larger area. It
would be more correct to calculate a mean bluff
recession distance for a given area measured over a
long period of time (i.e., years to decades). The long-
term rates should then be qualified with the amount
of recession that may occur during a given event (e.g.,
the average maximum recession distance). As an
example, for land-use management, it would be more
appropriate to use a long-term mean recession rate
over the horizon of interest to obtain a setback
distance, with an added buffer based on event-scale
recession.
Table 4. Annual sediment volume contribution (m
3
/yr) by drift
cell, 2001–2012.
Drift Cell
Mean
(m
3
/yr)
Mean +1 Standard
Deviation (m
3
/yr)
No. of
Transects Length (m)
Dungeness 103,000 232,000 433 13,625
Elwha 20,000 49,000 152 4,877
Table 5. Annual length-normalized sediment contribution (m
3
/m/yr) by drift cell, 2001–2012.
Drift Cell Mean (m
3
/m/yr)
Mean +1 Standard
Deviation (m
3
/m/yr) Maximum (m
3
/m/yr) No. of Transects Length (m)
Dungeness 7.5 17.0 11.3 433 13,625
Elwha 4.1 10.0 14.5 152 4,877
Coastal Bluff Recession
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 141
It should be emphasized that the bluff recession
distances reported in this study are derived from
selected elevations across the bluff-face profile,
which may not be seen by the homeowner at the
bluff top. While the trends are not likely to
significantly change, results will differ according to
the methods used to analyze bluff-face change.
Other methods of calculating bluff recession dis-
tances (e.g., contour change analysis, volume change
analysis) are expected to provide different results
than the profile-based methods used herein, and the
potential to produce alongshore averaging of bluff
recession rates over appropriate alongshore length
scales may result in less spatially variable rates that
are more conducive to land-use zoning, buffers, and
development setbacks. The bluff-face profile method
has the potential to accentuate the localized erosion
signals due to a lack of continuity along the bluff to
enable alongshore averaging commensurate with the
observed signals of change obtained at finer scale
along the bluff face.
While land-use planners and coastal managers are
in need of long-term erosion rates for prudent
resource management, property owners experience
localized erosion and tend to be most interested in
and concerned about the magnitude of bluff recession
occurring along relatively small increments of space
along their bluff-top property boundary.
Figure 11. Length-normalized sediment volume change (m
3
/m) in the highest 20 m of each beach topographic profile during four winter-to-
winter time intervals. EB-1 through BL-1 were winter surveys; BL-2 through DB-4 were summer surveys. Note that intervals 1–3 are annual,
whereas interval 4 spans 3 years.
Table 6. Beach topographic profile sediment volume changes for the Elwha drift cell. Note that the right-most column is net change between
2010 and 2013, while all others are annual intervals.
2010–2011 2011–2012 2012–2013 2010–2013
Profile
Volume Change
(m
3
/m)
Change Rate
(m/yr)
Volume Change
(m
3
/m)
Change Rate
(m/yr)
Volume Change
(m
3
/m)
Change Rate
(m/yr)
Volume Change
(m
3
/m)
Change Rate
(m/yr)
EB-1 213.54 20.69 2.42 0.12 24.89 1.19 13.77 0.23
EB-2 27.77 20.40 20.17 20.01 5.82 20.28 213.77 20.23
EB-3 212.33 20.66 1.87 0.09 22.06 20.11 212.66 20.22
EB-4 211.88 20.72 0.41 0.02 21.52 20.08 212.98 20.23
Average 211.38 20.62 1.13 0.06 3.87 0.18 26.41 20.11
Parks
142 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
Chronic sediment supply deficits in the Elwha drift
cell due to shoreline armoring have resulted in
significant habitat impairment on intertidal beaches
for forage fish and juvenile salmonids (Shaffer et al.,
2012; Parks et al., 2013). The removal of the two
Elwha River Dams will restore a significant compo-
nent of the Elwha littoral cell sediment supply. It is
currently unknown to what degree and over what
timescale Elwha River sediments will be stored on
intertidal beaches within the Elwha drift cell. Local
shoreline managers have an unprecedented opportu-
nity to optimize storage of Elwha River sediments on
intertidal beaches through implementation of selected
shoreline armoring removal and large-woody debris
placement strategies prior to the complete delivery of
Elwha River reservoir sediments into the intertidal
environment over the next 5–7 years.
In contrast to the impaired habitat function of
Elwha drift cell due to sediment starvation from
shoreline armoring and Elwha River Dams, the
Dungeness drift cell exhibits less than 1 percent by
length armored shoreline and highly functioning
forage fish spawning habitat (Shaffer et al., 2012;
Parks et al., 2013). The intact littoral sediment
supply processes from coastal bluff erosion within
the Dungeness drift cell are maintaining suitable
forage fish habitat (Parks et al., 2013) and expanding
the Dungeness Spit through sediment deposition
(Schwartz et al., 1987).
CONCLUSIONS
Rates of coastal bluff recession in the Dungeness
and Elwha drift cells over the 1939–2012 period were
highly variable in space and time and ranged between
0.31 m/yr and 1.88 m/yr. Differences between
maximum near-term bluff erosion rates observed
from 2001–2012 LiDAR and long-term (1939–2001)
observations from digitized historical photography
were the result of individual medium-scale landslides.
The presence of shoreline armoring is a controlling
factor on the rate of bluff recession, with armored
bluffs showing a reduced recession rate compared
with unarmored bluffs. The volume of sediment
produced by a unit length of unarmored bluff
shoreline is greater than that of armored bluffs by
factors of two (Elwha) and five (Dungeness), respec-
tively.
Sediment volumes contributed by bluffs in the
Elwha drift cell between 2001 and 2012 represent 11–
29 percent of the estimated fluvial sediment contri-
bution to the nearshore from the Elwha River prior to
dam construction in 1911. Annual sediment volumes
contributed by bluffs in the Elwha drift cell between
2001 and 2012 represent approximately 8–20 percent
of the current estimate (Gilbert and Link, 1995;
Bountry et al., 2010) of the long-term, post-dam
removal annual fluvial sediment contribution to the
nearshore from the Elwha River of about 2.5 3
10
5
m
3
/yr.
This study confirms that alteration to bluffs, in this
case armoring, drastically affects bluff recession rates
and sediment volume contributions to the nearshore.
Armored sections of bluffs showed significantly lower
rates (280 percent, Dungeness; 253 percent, Elwha)
of recession than did unarmored sections. Unarmored
sections of bluffs directly down-drift and adjacent to
armored sections experienced the highest rates of
bluff recession in the Elwha drift cell (1.88 m/yr) and
higher than mean rates (1.0 m/yr) in the Dungeness
drift cell.
It was beyond the scope of this study to determine
why there was a difference in sediment production
rates between the Elwha and Dungeness drift cells.
Geology, groundwater effects, wave-approach angle,
wave energy, and land use are all possible factors
explaining the observed differences, and these should
be further investigated in future studies.
Table 7. Beach topographic profile sediment volume changes for the Dungeness drift cell. Note that the right-most column is net change
between 2010 and 2013, whereas all others are annual intervals.
2010–2011 2011–2012 2012–2013 2010–2013
Profile
Volume Change
(m
3
/m)
Change Rate
(m/yr)
Volume Change
(m
3
/m)
Change Rate
(m/yr)
Volume Change
(m
3
/m)
Change Rate
(m/yr)
Volume
Change (m
3
/m)
Change Rate
(m/yr)
BC-1 23.87 20.20 25.37 20.24 22.63 20.16 211.86 20.20
BC-2 2.83 0.15 27.85 20.34 1.02 0.06 24.01 20.07
BL-1 210.47 20.43 28.57 20.38 23.67 20.23 222.72 20.36
BL-2 24.38 20.22 25.22 20.29 4.73 0.20 24.88 20.08
DB-1 28.56 20.43 22.07 20.12 21.22 20.05 211.84 20.20
DB-2 1.11 0.06 24.30 20.24 0.76 0.03 22.42 20.04
DB-3 212.23 20.79 0.48 0.03 2.02 0.08 29.73 20.17
DB-4 219.44 21.05 21.67 20.09 3.10 0.14 218.01 20.31
Average 26.88 20.36 24.32 20.21 0.51 0.01 210.68 20.18
Coastal Bluff Recession
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 143
While wave run-up and erosion at the base of
coastal bluffs is a dominant driving factor of erosion
throughout both drift cells, portions of each drift cell
also exhibited erosion in the upper one-third of the
bluff profile driven by a combination of precipitation,
local groundwater discharge, and relatively permeable
glacial strata overlying impermeable glacial strata.
The observed upper-bluff erosion driven by ground-
water and precipitation appears to be spatially and
temporally isolated from wave erosion, especially
where shore protection works are in place, and this
trend will continue whether the shoreline is armored
or not.
At present, it remains challenging to make reliable
projections of bluff recession that may guide devel-
opment setback distances for the future, given the
coarse resolution of a multi-decadal interval (aerial
photos for 1939–2001) and only one higher-resolution
decadal interval (airborne LiDAR data for 2001–
2012). The combination of chronic recession rates and
event-based erosion magnitudes is important for
decision makers, and the most reliable rates will
come from a longer-term high-resolution data set that
must be developed over time.
The results of this study provide estimates for
minimum setback distances between structures and
bluff edges based on long-term mean recession rates
measured over the scale of an entire drift cell. This
type of information provides the scientific basis that
land-use planners and government regulators need
in order to develop sound long-term management
policies for bluff development.
Recession distances measured for a specific point
along the bluff may not represent the trends observed
over the larger drift-cell area and over a longer period
of time. It would be more correct to calculate a mean
bluff recession distance for a given area measured
over a long period of time (i.e., years to decades). The
long-term rates should then be qualified with the
amount of recession that may occur during a given
event (e.g., the average maximum recession distance).
As an example, for land-use management, it would be
more appropriate to use a long-term mean recession
rate over the horizon of interest to obtain a setback
distance with an added buffer based on event-scale
recession.
Repeat surveys performed at relatively short
intervals would enable a better determination of the
relative importance of a variety of mechanisms
contributing to bluff erosion, such as surface runoff
(and associated land-clearing and development prac-
tices), wind, precipitation, groundwater discharge,
soil saturation, wave height and direction, total water
level, beach width and elevation, and littoral sediment
supply. All of these factors play a role in bluff retreat
dynamics, and measurement of these parameters
combined with high-resolution bluff-face topography
and differences over time will enable the development
of improved process-based bluff erosion models (Lee
et al., 2001; Castedo et al., 2012).
ACKNOWLEDGMENTS
This study benefited from discussions with Anne
Shaffer (Coastal Watershed Institute), Jon Warrick
(USGS), and Hugh Shipman (WDOE) on coastal
processes and sediment budgets along the Central
Strait of Juan de Fuca. Jesse Wagner and Wade
Raynes (Western Washington University) and Clinton
Stipek (University of Washington) provided field and
technical support. Western Washington University
and Peninsula College provided field equipment and
student interns. Anne Shaffer (Coastal Watershed
Institute) provided vital overall support, coordination,
and integration with other project components.
Diana McCandless, Washington Department of
Ecology Coastal Mapping Program, provided analy-
sis of beach erosion data. Heather Baron, Matt
Brunengo, Kerry Cato, Wendy Gerstel, Amanda
Hacking, Michael W. Hart, George Kaminsky, and
Keith Loague provided helpful reviews.
We want to sincerely thank Ruth Jenkins, John
Warrick, Chris Saari, Paul Opionuk, Pam Lowry,
Connie and Pat Schoen, Hearst Cohen, Malcolm
Dudley, Nippon Paper, and the Lower Elwha
S’Klallam Tribe for access across private property.
Dungeness National Wildlife Refuge personnel and
volunteers provided access and transportation.
Student interns were funded by the U.S. Environ-
mental Protection Agency under grant number PC-
00J29801-0 awarded to the Washington Department
of Fish and Wildlife (contract number 10-1744) and
managed by the Coastal Watershed Institute. Fund-
ing for student interns and GPS equipment used to
collect beach profiles were provided by the Clallam
County Marine Resources Committee and by the
Environmental Protection Agency grant listed above.
Any opinions, findings and conclusions, or recom-
mendations expressed in this material are those of the
author and do not necessarily reflect the views of the
Environmental Protection Agency or the Washington
Department of Natural Resources.
REFERENCES
BIKFALVI, 2012, ABOXPLOT, Advanced Boxplot Routine for
MATLAB: Electronic document, available at http://alex.
bikfalvi.com/research/advanced_matlab_boxplot/
BOOTH, D. B.; TROOST, K. G.; CLAGUE, J. J.; AND WAITT, R. B.,
2003, The Cordilleran ice sheet: Development Quaternary
Science, Vol. 1, pp. 17–43.
Parks
144 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
BOUNTRY, J. A.; FERRARI, R.; WILLE, K.; AND RANDLE, T. J., 2010,
2010 Survey Report and Area-Capacity Tables for Lake Mills
and Lake Aldwell on the Elwha River, Washington: U.S.
Department of Interior, Bureau of Reclamation, Technical
Service Center, Report No. SRH-2010-23, 66 p.
BRADLEY, W. C., 1963, Large-scale exfoliation in massive
sandstones of the Colorado Plateau: Geological Society
America Bulletin, Vol. 74, pp. 519–528.
CARSON,M.A.AND KIRKBY, M. J., 1972, Hillslope Form and
Processes: Cambridge University Press, Cambridge, MA,
475 p.
CASTEDO, R.; MURPHY, W.; LAWRENCE, J.; AND PAREDES, C., 2012,
A new process-response coastal recession model of soft rock
cliffs: Geomorphology, Vol. 177–178, pp. 128–143.
COLLINS,B.D.AND SITAR, N., 2008, Processes of coastal bluff
erosion in weakly lithified sands, Pacifica, California, USA:
Geomorphology, Vol. 97, No. 3–4, pp. 483–501.
DETHIER, D. P.; PESSL, F., JR.; KEULER, R. F.; BALZARINI, M. A.;
AND PEVEAR, D. R., 1995, Late Wisconsinan glaciomarine
deposition and isostatic rebound, northern Puget Lowland,
Washington: Geological Society America Bulletin, Vol. 107,
No. 11, pp. 1288–1303.
DOWNING, J., 1983, The Coast of Puget Sound: Its Processes and
Development: University of Washington Press, Seattle, WA,
126 p.
DROST, B. W., 1986, Water Resources of Clallam County,
Washington: U.S. Geological Survey Water Resources
Investigations Report 83-4227, 263 p.
EAST, A. E.; PESS, G. R.; BOUNTRY, J. A.; MAGIRL, C. S.; RITCHIE,
A. C.; LOGAN, J. B.; RANDLE, T. J.; MASTIN, M. C.; MINEAR,
J. T.; DUDA, J. J.; LIERMANN, M. C.; MCHENRY, M. L.;
BEECHIE, T. J.; AND SHAFROTH, P. B., 2014, Large-scale dam
removal on the Elwha River, Washington, USA: River
channel and floodplain geomorphic change: Geomorphology:
In Press, doi:0.1016/j.geomorph.2014.08.028
FINLAYSON, D., 2006, The Geomorphology of Puget Sound Beaches:
Puget Sound Nearshore Partnership Report No. 2006-02,
Washington Sea Grant Program, University of Washington,
Seattle, WA, 45 p.
GALSTER, R. W., 1989, Ediz Hook—A Case History of Coastal
Erosion and Mitigation. Engineering Geology in Washington,
Vol. 2: Washington Division of Geology and Earth
Resources Bulletin 78, Washington Department of Natural
Resources, Olympia, WA, pp. 1177–1186.
GALSTER,R.W.AND SCHWARTZ, M. L., 1989, Ediz Hook—A case
history of coastal erosion and rehabilitation. In Schwartz,
M. L. and Bird, E. C. F. (Editors), Artificial beaches: Journal
Coastal Research, Special Issue 6, pp. 103–113.
GELFENBAUM, G.; STEVENS, A.; ELIAS, E.; AND WARRICK, J., 2009,
Modeling sediment transport and delta morphology on the
dammed Elwha River, Washington State, USA: Coastal
Dynamics: Paper No. 109, 15 p.
GELFENBAUM, G. R.; STEVENS, A.; MILLER, I.; AND WARRICK, J. A.,
2014, Large-scale dam removal on the Elwha River,
Washington, USA: Coastal geomorphic change: Geomor-
phology: in review.
GILBERT,J.AND LINK, R. A., 1995, Alluvium Distribution in Lake
Mills, Glines Canyon Project and Lake Aldwell, Elwha Project,
Washington: U.S. Department of Interior, Elwha Technical
Series PN-95-4, 60 p.
HAMPTON, M. A., 2002, Gravitational failure of sea cliffs in weakly
lithified sediment: Environmental Engineering Geoscience,
Vol. 8, No. 3, pp. 175–191.
HAPKE, C., 2004, The measurement and interpretation of coastal
cliff and bluff retreat. In Hampton, M. and Griggs, G.
(Editors), Formation, Evolution, and Stability of Coastal
Cliffs—Status and Trends: U.S. Geological Survey Profes-
sional Paper 1693, pp. 39–50.
HAPKE,C.J.AND PLANT, N., 2010, Predicting coastal cliff erosion
using a Bayesian probabilistic model: Marine Geology,
Vol. 278, pp. 140–149.
JOHANNESSEN,J.AND MACLENNAN, A., 2007, Beaches and Bluffs of
Puget Sound: Puget Sound Nearshore Partnership Report
No. 2007-04, Seattle District, U.S. Army Corps of Engineers,
Seattle, WA, 34 p.
JONES, M. A., 1996, Delineation of Hydrogeologic Units in the
Lower Dungeness River Basin, Clallam County, Washington:
U.S. Geological Survey, Water Resources Investigation
Report 95-4008, 11 p.
KEULER, R. F., 1988, Map Showing Coastal Erosion, Sediment
Supply, and Longshore Transport in the Port Townsend 30-by-
60-Minute Quadrangle, Puget Sound Region, Washington:
U.S. Geologic Survey Miscellaneous Investigation Map I-
1198-E, scale 1:100,000.
LEE, E. M.; HALL, J. W.; AND MEADOWCROFT, I. C., 2001, Coastal
cliff recession: The use of probabilistic prediction methods:
Geomorphology, Vol. 40, pp. 253–269.
MILLER, I. M.; WARRICK, J. A.; AND MORGAN, C., 2011,
Observations of coarse sediment movements on the mixed
beach of the Elwha Delta, Washington: Marine Geology,
Vol. 282, No. 3–4, pp. 201–214.
MOSHER,D.C.AND HEWITT, A. T., 2004, Late Quaternary
deglaciation and sea-level history of eastern Juan de Fuca
Strait, Cascadia: Quaternary International, Vol. 121, pp. 23–
39.
NATIONAL CLIMATE DATA CENTER (NCDC), 2014, Climate
Summaries for Port Angeles and Sequim, Washington:
Electronic document available at http://www.ncdc.noaa.gov/
NATIONAL OCEANIC and ATMOSPHERIC ADMINISTRATION (NOAA),
2013, Tidal Data for Port Angeles, Washington, Station 9444090;
Electronic document available at http://tidesandcurrents.noaa.
gov/stationhome.html?id59444090
PARKS, D.; SHAFFER, A.; AND BARRY, D., 2013, Nearshore drift-cell
sediment processes and ecological function for forage fish:
Implications for ecological restoration of impaired Pacific
Northwest marine ecosystems: Journal Coastal Research,
Vol. 29, No. 4, pp. 984–997.
PETTIT, M. M.; THOMAS, M. A.; AND LOAGUE, K., 2014, Retreat of
a coastal bluff in Pacifica, California: Environmental Engi-
neering Geoscience, Vol. 20, No. 2, pp. 153–162.
POLENZ, M.; WEGMANN, K. W.; AND SCHASSE, H. W., 2004,
Geologic Map of the Elwha and Angeles Point 7.5-Minute
Quadrangles, Clallam County, Washington: Washington
Division of Geology and Earth Resources, Open File Report
2004-14.
PUGET SOUND LIDAR CONSORTIUM (PSLC), 2001, Topographic
LiDAR: PSLC, Clallam County, WA.
RANDLE, T. J.; YOUNG, C. A.; MELENA, J. T.; AND OUELLETTE,
E. M., 1996, Sediment Analysis and Modeling of the River
Erosion Alternative: U.S. Bureau of Reclamation, Pacific
Northwest Region, Elwha Technical Series PN-95-9, 138 p.
RICE, C. A., 2006, Effects of shoreline modification on a northern
Puget Sound beach: Microclimate and embryo mortality in
surf smelt (Hypomesus pretiosus): Estuaries Coasts, Vol. 29,
No. 1, pp. 63–71.
ROGERS, H. E.; SWANSON, T. W.; AND STONE, J. O., 2012, Long-
term shoreline retreat rates on Whidbey Island, Washington,
USA: Quarternary Research: doi:10.1016/j.yqres.2012.06.001
SCHASSE, H. W., 2003, Geologic Map of the Washington Portion of
the Port Angeles 1:100,000 Quadrangle: Washington Division
of Geology and Earth Resources, Open File Report 2003-6,
Coastal Bluff Recession
Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146 145
Washington Department of Natural Resources, Olympia,
WA.
SCHASSE,H.W.AND POLENZ, M., 2002, Geologic Map of the Morse
Creek 7.5-Minute Quadrangle, Clallam County, Washington:
Washington Division of Geology and Earth Resources, Open
File Report 2002-8, Washington Department of Natural
Resources, Olympia, WA.
SCHASSE, H. W.; POLENZ, M.; AND WEGMANN, K. W., 2000,
Geologic Map of the Carlsborg 7.5-Minute Quadrangle,
Clallam County, Washington: Washington Division of Geol-
ogy and Earth Resources, Open File Report 2000-7,
Washington Department of Natural Resources, Olympia,
WA.
SCHUENEMEYER,J.H.AND DREW, L. J., 2011, Statistics for Earth
and Environmental Scientists: John Wiley & Sons, Inc.,
Hoboken, NJ, 407 p.
SCHWARTZ, M. L.; FABBRI, P.; AND WALLACE, R. S., 1987,
Geomorphology of Dungeness Spit, Washington, USA:
Journal Coastal Research, Vol. 3, No. 4, pp. 451–455.
SCHWARTZ, M. L.; WALLACE, R. S.; AND JACOBSEN, E. E., 1989, Net
shore-drift in Puget Sound, Engineering Geology in Wash-
ington, Vol. 2, Olympia, WA: Washington Division Geology
Earth Resources Bulletin 78: Washington Department of
Natural Resources, pp. 1137–1146.
SHAFFER, J. A.; CRAIN, P.; KASSLER, T.; PENTTILA, D.; AND BARRY,
D., 2012, Geomorphic habitat type, drift cell, forage fish and
juvenile salmon; are they linked? Journal Environmental
Science Engineering, Vol. 1, No. 5a, pp. 688–703.
SHIPMAN, H., 2004, Coastal bluffs and sea cliffs on Puget Sound,
Washington. In Hampton, M. A. and Griggs, G. B. (Editors),
Formation, Evolution and Stability of Coastal Cliffs—Status
and Trends: U.S. Geological Survey Professional Paper 1693,
123 p.
SHIPMAN, H.; DETHIER, M. N.; GELFENBAUM, G.; FRESH, K. L.; AND
DINICOLA, R. S. (Editors), 2010, Puget Sound shorelines and
the impacts of armoring: Proceedings of the State of the
Science Workshop, May 2009, Menlo Park, CA: U.S.
Geological Survey Scientific Investigations Report 2010-
5254, 262 p.
U.S. ARMY CORPS OF ENGINEERS (USACE), 1971, Report on Survey
of Ediz Hook for Beach Erosion and Related Purposes. Port
Angeles, Washington: Department of the Army, Seattle
District, Corps of Engineers, 96 p.
VARNES, D. J., 1978, Slope movement types and processes. In
Clark, M. (Editor), Landslide Analysis and Control: Special
Report 176, Transportation Research Board, National
Academy of Sciences, National Research Council, Washing-
ton, DC, pp. 11–33.
WALKDEN,M.J.A.AND HALL, J. W., 2005, A predictive Mesoscale
model of the erosion and profile development of soft rock
shores: Coastal Engineering, Vol. 52, pp. 535–563.
WARRICK, J. A.; BOUNTRY, J. A.; EAST, A. E.; MAGIRL, C. S.;
RANDLE, T. J.; GELFENBAUM, G. R.; RITCHIE, A. C.; PESS,
G. R.; LEUNG, V.; AND DUDA, J. J., 2014, Large-scale dam
removal on the Elwha River, Washington, USA: Source to
sink sediment budget and synthesis. Geomorphology:in
review.
WARRICK, J. A.; GEORGE, D. A.; GELFENBAUM, G.; RUGGIERO, P.;
KAMINSKY, G. M.; AND BEIRNE, M., 2009, Beach morphology
and change along the mixed grain-size delta of the dammed
Elwha River, Washington: Geomorphology, Vol. 111, pp. 136–
148.
WOOLPERT,INC., 2013, Elwha River, WA LiDAR, United States
Geological Survey (USGS). Contract No.: G10PC00057.
Woolpert, Inc.)Englewood, CO, 11 p.
YOTTER-BROWN,C.W.AND FAUX, R., 2012, LiDAR Remote
Sensing, Jefferson and Clallam Counties, Washington: Puget
Sound LiDAR Consortium, Seattle, WA, 29 p.
YOUNG,A.P.AND ASHFORD, S. A., 2007, Quantifying sub-regional
seacliff erosion using mobile terrestrial LiDAR: Shore Beach,
Vol. 75, No. 3, pp. 38–43.
YOUNG, A. P.; GUZA, R. T.; O’REILLY, W. C.; FLICK, R. E.; AND
GUTIERREZ, R., 2011, Short-term retreat statistics of a slowly
eroding coastal cliff: Natural Hazards Earth System Sciences,
Vol. 11, pp. 205–217.
YOUNG, A. P.; OLSEN, M. J.; DRISCOLL, N.; GUTIERREZ, R.; GUZA,
R. T.; FLICK, R. E.; JOHNSTONE, E.; AND KUESTER, F., 2009,
Comparison of airborne and terrestrial LiDAR estimates of
seacliff erosion in Southern California: Photogrammetric
Engineering Remote Sensing, Vol. 76, No. 4, pp. 421–426.
YOUNG, A. P.; RAYMOND, J. H.; SORENSON, J.; JOHNSTONE, E. A.;
DRISCOLL, N. W.; FLICK, R. E.; AND GUZA, R. T., 2010,
Coarse sediment yields from seacliff erosion in the Oceanside
Littoral Cell: Journal Coastal Research, Vol. 26, No. 3,
pp. 580–585.
ZILKOSKI, D. B.; RICHARDS, J. H.; AND YOUNG, G. M., 1992,
Results of the general adjustment of the North American
vertical datum of 1988, (NAVD 88): American Congress
Surveying Mapping, Surveying Land Information Systems,
Vol. 52, No. 3, pp. 133–149.
Parks
146 Environmental & Engineering Geoscience, Vol. XXI, No. 2, May 2015, pp. 129–146
... Much of the physical process monitoring and modeling work informative but not designed to address specific nearshore restoration planning questions (sediment trajectory and fate specific to shoreline and lower river alterations). Norris et al. 2007, Shaffer et al. 2009, Shaffer et al. 2012, Quinn et al. 2013aand b, Parks et al. 2013, Flores et al. 2014, Rich et al. 2014, Weifferling 2014, Parks 2015 • 91 Shaffer et al. 2009, 2012, Rich et al. 2014, Weifferling 2014 Post dam removal assessment of nearshore restoration and next steps. ...
... Major impacts to the Elwha nearshore ecosystem directly related to the dam removals include ongoing shoreline armoring, lower river alterations, and in-river dams (Shaffer et al. 2008). As a result, the Elwha bluff and spit beaches are steep, with coarsened substrate and more variable grain size than comparable intact drift cells , Parks 2015. Furthermore, dikes and shoreline-armoring remain after dam removal, resulting in only a partial restoration in the Elwha nearshore. ...
... This includes identifying and resolving important additional nearshore disrupting features within the dam removal drift cell. Nearshore habitat restoration from dam removals can be disrupted by dikes and shoreline armoring remaining in the nearshore during and after dam removal (Parks 2015). These features should therefore be clearly identified and incorporated as important components of large-scale dam removal restoration. ...
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Large dam removals are emerging as an important ecosystem restoration tool, and they often have direct influence on the marine nearshore zone, but dam removal plans give little consideration to nearshore restoration. We provide an overview of the relationship between large-scale dam removals and nearshore restoration, using the Elwha dam removal project, in Washington State, United States, as a basis. The following steps are essential for incorporating nearshore restoration planning into future dam removals: 1) Conceptual and technical modeling of nearshore physical and ecological processes at the drift cell scale to define nearshore priorities and geographic areas to be conserved or restored; 2) Acquiring seasonal field data to inform models, including: water quality; sediment delivery volumes, timing, trajectory and composition; and basic fish community data such as abundance, size, species composition, and trophic components; 3) Mapping nearshore habitat areal extent and ecological function prior to, during, and after dam removal, including vegetation composition and invertebrate community composition; 4) Defining and addressing the implications of habitat barriers and fish management actions for nearshore ecosystem function prior to dam removal. Structures and hatchery practices that conflict with nearshore ecosystem function for wild species prior to, during, and after dam removal should be identified and eliminated; 5) Anticipating nearshore invasive species colonization as a result of dam removal; 6) Developing and implementing long-term adaptive management plans to ensure nearshore restoration goals are identified and met. These steps must begin as early as possible in the planning process.
... As of September 2015, approximately 2.6x106 m3 of sediment material has resulted in over 35 ha of new delta habitat, and increased the total area of the Elwha delta to over 150 ha (Shaffer et al., 2017a;Fig. 3); 3. Along the delta and lower river, there was an almost immediate shift in original habitats from tidally influenced to non-tidally influenced Dam removal as a management strategy for fisheries recovery: lessons from the Elwha River nearshore and implications for Formosa landlocked salmon habitats, resulting in changes in resident fish communities (Shaffer et al., 2017b, Foley et al., 2017; 4. Despite being a sediment-starved system, restoration along most of the Elwha nearshore was only partially due to remaining impediments including lower river dikes and shoreline armoring (Parks et al., 2013;Parks, 2015;Shaffer et al., 2009;Shaffer et al., 2017a). ...
... Along the Elwha drift cell, surf smelt (Hypomesus pretiosus) and Pacific sand lance (Ammodytes personatus) are two species of forage fish that spawn along intertidal reaches of very specific grain size beaches. This function is disrupted due to sediment starvation associated with a combination of large-scale dams and armoring of feeder bluffs (Parks et al., 2013;Parks, 2015;Wefferling, 2015). Forage fish spawning response to dam removal appears to be complex and may be related to multiple factors including high inter-annual variability in physical habitat conditions, geographic factors and complex life histories of forage fish (Shaffer et al. in prep). ...
... Le marnage moyen ressortégalement ressortégalement dans l'analyse random forest commequatrì eme variable explicative. Ce type de marnage est présent dans la base de données au Royaume Uni ( Brown et al., 2012;Bray et Hooke, 1997;Lee, 2005Lee, , 2008 ; en Californie ( Parks, 2015;Moore et al., 1999;Moore et Griggs, 2002) ; au Portugal ( Correia et al.;Teixeira, 2006;Regnauld et al., 1995;Dias et Neal, 1992;Cruz de Oliveira et al., 2008) ; en Espagne (Del Río et Gracia, 2009;Anfuso et al., 2007) ; en France ( ; en Corée du Sud ( ) et enfin en Nouvelle Zélande ). ...
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Cette thèse a pour but de comprendre quels processus contrôlent l'érosion des falaises côtières à deux échelles spatiales. Nous avons d'abord réalisé une étude locale de la falaise de flysch de Socoa (Pays Basque), dont la spécificité est un fort contrôle structural. Elle a été suivie annuellement par photogrammétrie pendant 6 ans. Cette falaise résistante recule lentement, à 3,4 mm/an. Son erosion est le fait de départ de blocs, majoritairement au niveau des arêtes libres. Ensuite, afin d'aborder l'échelle globale, une base de données (GlobR2C2, Global Recession Rates of Coastal Cliffs) a été créée. Elle est la première à recenser les taux d'érosion publiés et à les comparer à des forçages météo-marins issus de grilles mondiales. Nous l'avons traitée par analyse statistique exploratoire et par random forest. La résistance de la roche parait être le premier facteur contrôlant le taux d'érosion. Au second ordre, apparaissent le nombre de jours de gel par an et le marnage.
... Between the river delta plain and the base of Ediz Hook, glacial-till bluffs rise landward of the beach. Their erosion is an additional source of littoral-grade (sand and gravel) sediment to the shoreline, although the rate of this sediment input has been reduced owing to ~4 km of armoring along the eastern portion of the bluffs 38 (Fig. 1c). (d) Directional histograms of significant wave heights of swell and seas characterized by 4 years of wave spectra measured at two sites offshore of the river mouth. ...
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... This source-to-sink approach oversimplifies the development of depositional environments located away from the main axis (Fig. 1). Longshore drift, for example, transports sediments towards off-axis systems, such as in the case of the northern shores of Washington State (Parks, 2015). However, in most cases local rivers along the course of the drift obscure its sedimentary contribution to the off-axis system. ...
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