ASBPA 2012 – San Diego, CA
Proposed Abstract for Oral Presentation
Working with Nature
Working with Nature to Implement Regional Sediment Management
at the Mouth of the Columbia River – A Nearshore Perspective
Katharine Groth1, Hans Moritz1, Jarod Norton1, Michael Ott1
The proposed presentation will discuss how dredged material is to be placed within a nearshore location
adjacent to the Mouth of the Columbia River (MCR), to address a chronic coastal sediment deficit while
minimizing impacts to the site’s benthic ecology. The South Jetty Site (SJS) is a new nearshore site to be
permitted under Section 404 of the Clean Water Act. The dredged sediment to be placed within the SJS
originates from the MCR federal navigation channel and is classified as fine-medium sand (average D50
= 0.2 mm), having less than 3% fines content. The areal extent of the SJS is approximately 7,000 ft x
7,000 ft and the site is located 1 mile south of the MCR inlet in water depth of 40 to 60 ft. The SJS is
expected to be used operationally for the first time during late summer 2012. The permitting action and
development of an operational use plan for the SJS was the result of active collaboration with regional
stakeholders, based on the need to implement Regional Sediment Management at the MCR inlet.
Featured elements of the presentation will describe: A) the operational use for the proposed nearhore site,
B) the metrics used to assess disposal site performance, and C) an integrated monitoring program for
evaluating the physical and biological effects of dredged placement within the nearshore.
The nearshore morphology along the south side of the MCR inlet has been receding for many
decades. In additional to compromising the stability of the jetties and the MCR inlet & navigation
channel, progressive loss of shoreface morphology at the MCR degrades the benthic substrate for
nearshore ecology. Regional sediment management (RSM) is being implemented at MCR to maximize
the beneficial use of dredged sediment to sustain the littoral budget of the inlet and adjacent coastal zone.
Use of SJS is an RSM-based initiative which is expected to re-introduce sand dredged from the MCR,
into the littoral area south of the inlet. Realized benefits of the SJS will address an ongoing sediment
deficit affecting the nearshore & foreshore areas along the south jetty, the foundation stability of the south
jetty, and locations further south of the MCR inlet.
Placement of 300,000 cy of dredged sand within the SJS is to commence after 15 Aug 2012,
which is the when crab season is closed along Oregon coastal waters. The objective for dredged material
placement within the SJS is to supplement the deficient littoral sediment budget south of MCR with
dredged sand, while minimizing impacts to benthic infauna and epibenthic community of the SJS. To
promote dispersal of dredged material on the seabed of the SJS (and minimize benthic impacts), a method
of thin-layer dredged material placement will be used, such that maximum deposition thickness per load
placed is less than 0.25 ft. Additionally, the overlapping of disposal events (dump tracks) will be
minimized to avoid overlapping of successive disposal events within a given 72 hour period. The
seasonal distribution of dredged material placement within the overall SJS will be executed such that the
total season accumulation within the SJS (at the conclusion of the 2012 dredging season) will be 1 ft or
less. A cell-based utilization plan (similar for the SWS) will be used to guide dredged material placement
within the SJS, to achieve the SJS use objectives described above. Within the SJS, each hopper dredge
load of dredged sand will be distributed along a placement track no less than 5,000 feet, and no more than
10% of a hopper dredge load shall be placed within any 500-ft transit distance. A variety of collaborative
monitoring techniques will be used to verify that the above operational (dredged material placement)
metrics are realized.
1=U.S.
Army
Corps
of
Engineers-Portland
District,
503.808.4864,
PO
Box
2946,
Portland,
OR
97208
hans.r.moritz@usace.army.mil. jarod.k.norton@usace.army.mil. michael.e.ott@usace.army.mil Katharine.c.groth@usace.army.mil
ASBPA 2012 – San Diego, CA
Proposed Abstract for Oral Presentation
Working with Nature
Katharine Groth
Ms. Groth has worked at the Portland District Corps of Engineers for 4 years as a Project
Manager and for the Norfolk District Corps of Engineers for 3 years as an economist. Ms. Groth
currently manages the twelve shallow and deep draft coastal navigation projects on the Oregon
coast, south of the Columbia River. She obtained a Master of Science degree in Natural Resource
Economics from Oregon State University in 2000.
1=U.S.
Army
Corps
of
Engineers-Portland
District,
503.808.4864,
PO
Box
2946,
Portland,
OR
97208
hans.r.moritz@usace.army.mil. jarod.k.norton@usace.army.mil. michael.e.ott@usace.army.mil Katharine.c.groth@usace.army.mil