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Monterey Bay Seawalls
page last modified on
10 / 4 / 2014

__________________________

Technical Reports:
Stable Shorelines & Broad Beaches in Southern Monterey Bay (2.8 Mb)
Coastal Erosion & Armoring in Southern Monterey Bay (2.3 Mb)

Fort Ord Dunes State Park

Click on the thumbnails below to see a larger images.

CSU Monterey Bay students of Science & Environmental Policy benefit from learning in classrooms where active tectonics, dynamic ocean systems, and diverse ecosystems compose the modern blackboard. We use that context for an open dialogue on environmental policy issues.

One issue presenting itself to the local community is the policy of constructing seawalls to protect buildings that have been constructed too close to the dynamic ocean-land interface.

This web page will be updated on occasion, as new information becomes available about the interface of our cultural infrastructure and the sea.

Geomorphic Systems students watch 15-20 foot swells rearrange the Monterey Bay beaches...
...during the first storm of the 2002-2003 season.

Seawall at Monterey Beach Hotel on 11/8/02.

Note that the seawall precludes safe foot-traffic along the beach during these conditions.

Seawalls tend to reflect energy back to the shoreface, focusing, rather than reducing, erosive forces.
This is the seawall on 11/08/02.
This is the same view as above on 11/11/02, 3 days later. Note net sand loss. Compare this with photos taken one month later, after the sidewall collapsed and large riprap was used to fortify the base.

Each summer, weak but consistent wave energy gradually builds a broad flat beach as sand is slowly moved from off-shore sandbars up to the shoreface.

Each winter, the mixture of wave energy and wave frequencies erodes the summer beaches, moving the sand to be stored in off-shore bars.

This is the seawall on about 12/21/02 soon after the parking lot was undercut. Large riprap was placed on the sides and front of the seawall to protect the hotel.

This is the same day as above.

Note that the seawall precludes safe foot-traffic along the beach during these conditions. This is the "Peninsula Effect" that blocks people and sand migration.

Same day as above. Note that much more sand is eroded from right next to the seawall than from where the picture was taken. This is evidence that the structure accelerates sand erosion from the beach.
By March 5, 2003, after most of the hard winter storms had passed, the sand berm had built back up to cover the base of wall. Seasonal beach replenishment is a natural part of the annual cycle.
This is a closer view the same day as above.
This is a closer view on the same day as above.
Feb 29, 2004 shows the summer beach replaced by the winter beach. Note the deep shoreward indentation in the beach near the hotel. The coastline is retreating 0.7 m/yr here, so the seawall is left sticking out in the surf.
November 19, 2004 shows the 2004 summer beach washing away to the winter beach.
December 9, 2004 during one of the first big wave days of the winter 13.5 ft swells @ 16 sec period. This swell, combined with a tide of 5.98 ft, shows the hotel with a pronounced "peninsula effect."
hotel October 18, 2007 during one of the first big wave days of the fall 11 ft swells and a rising tide. Access was cut off for the first time in several months as the tide rose.
hotel Same as above. The large rip-rap buttresseing the corner is still mostly buried, but the swash zone was beginning to cut away the summer beach berm.
hotel January 5, 2008. The rip-rap along the seawall is exposed during a combination of high tide and storm surf.
hotel Same as above with peninsula effect precluding passage in front of hotel. Stanchions in foreground supported a fence protecting dune habitat. Coastal retreat is reducing the width of dune habitat all along the southern Monterey Bay coast.
The "peninsula effect" is also apparent in this digital evevation model produced from 2003 NOAA LIDAR data. The rectangular outline of the hotel "footprint" juts into the beach and nearshore environment.
2004--Not far away, at Del Monte Beach, the Ocean Harbor House Condominiums are facing similar problems. The owners are seeking permits for a seawall structure. This is a close up of exposed support pilings. Some of the pilings appear to be dangling upon closer inspection.
new wall October 18, 2007--Condo-owners received a permit to construct a sheet piling and rock seawall to protect their properties. Coastal Commission levied a 2.1 million dollar mitigation fee for this project. Swash was splashing on the wall and construction equipment.
new wall June 21, 2008--Temporary rock seawall (above) is now being replaces with a permanent seawall. Condo owners may appeal the mitigation fee.
new wall June 21, 2008--View toward Monterey past the Harbor House condominiums shows pinched bach during sea wall construction.
new wall June 21, 2008--Exposed drainage pipe adjacent to the Harbor House Condos is a clear indication of approximate 0.5 m/yr coastal retreat experienced by this reach of coastline.
new wall

June 21, 2008--Very rare summer thunderstorm produced lightening strikes beyond Harbor House Condominiums. (Digital photograph with contrast and brightness adjusted to highlight lightening bolt)

Just west of CSUMB campus the coast is retreating at an asonishing 2 m/yr. A seawall was erected here to protect Stillwell Hall on old Fort Ord. Photo taken 04/98 by USGS.
Stillwell Hall shows the classic "Peninsula Effect" in this photo taken near the 2002/03 change. A once wide beach is now deep water in front of a sea wall. Note the rapid erosion that occurred between the previous photo (1998) and this one. Photo by Marc Edwards (USACE).
Same as above, showing northwest edge of Stillwell Hall. Note that the sea is getting behind the seawall; the seawall will become an island, then a reef, then will be buried in the continental shelf sands as the coast retreats. Photo by Marc Edwards (USACE).

10/31/2004 oblique aerial view shows that Stillwell Hall was dismantled and removed from the cliff top. The riprap seawall was also removed. Only the ashpalt parking lot remains at this time.

There are two long-term natural processes that work against seawalls, erosion and submergence. As sea level continues its rise, and seacliffs continue their retreat, the beaches on either side of a seawall will continue to erode back, leaving the seawall as a promontory to be battered by large waves. Eventually, seawalls and other hard structures, will be left stranded in the sea. We find ancient ruins submerged along the shores of the Mediterranean as a clear monument to the commonly futile struggle between human culture and global sea level change. A triumphant battle against the sea is likely temporary.

Most of Monterey coast is naturally retreating. We have animated sea level rise and coastal retreat for the past 18,000 years in the linked "avi" animation (3.6 MB) made from offshore and onshore virtual landscapes of Monterey Bay. Modern coastal retreat rates as high as 2 m/yr have been assessed by a few workers, including SEP student, Karen Gref (2.7 Mb pdf).

The images of Stillwell Hall show that local hard structures reduce coastal retreat only locally, and only for a while. With time they will be left behind in the sea. Monterey beach erosion policy must work around those few facts.


Monterey Bay headlines

2002
Hereald article: Harbor House Condominiums

2003
Herald article: Harbor House Condos and seawalls
Herald article: Harbor House Condos seawall at planning commission
Herald article: Harbor House seawall poor environmental review
Herald article: Harbor House seawall spawns broader discussion
Herald Guest Commentary: Urban beaches need protection
Herald Letter to the Editor: Stop the Seawall
Herlad article: City Council to vote on Harbor House seawall
Herald article: Thornton lays out alteratives for City Council
Herlad article: Opinion....Monterey needs beach erosion policy
Herald article: City Council OKs Harbor House Seawall
Seawalls for golf courses
Summary article in Santa Cruz's Good Times Newspaper
Up to one million $$ sought to repair seawalls and hard structures protecting beach trails

2004
Herald article: Coastal Commission OKs Harbor House Seawall with $5.3 million mitigation
Herald article: Harbor House Condo Owners unhappy with mitigation fee
Herald article: Monterey City endorses protest letter regarding mitigation fee

2007
Herald article: Coastal Commission OKs Harbor House Seawall with $5.3 million mitigation. The actual fee paid will be $2.1 million, if paid up front, rather than over the 50 year life of the project. Condo-owners are elated; Sierra Club notes that the compensation cannot replace that stretch of Monterey coastline. The mitigation fee is still being appealed. March 21, 2007.
Herald article: Santa Cruz moving forward to armor Sea Cliff Drive March 21, 2007.

2008
Herald article: Condominium owners at Ocean Harbor House on Monterey Beach will have to pay $2.15 million plus legal fees to the California Coastal Commission as compensation for their seawall, the state Court of Appeal has ruled.
Herald article: Condominium owners at Ocean Harbor House may appeal the $2.15 million mitigation fee. The fee would go to Monterey Peninsula Regional Park District to purchase beach property for public use. Final seawall construction has commenced in front of the condos..




Photo documentation of relevant coastal processes
Ano Nuevo sea cliff retreat caught in action on 2/17/03
High-resolution photo-documentation of the California Coast
More coastal photos between Ano Nuevo and Santa Cruz


Technical information about seawalls, coastal erosion, sea level, etc.

U.S. Army Corps of Engineers
Coastal and Hydraulics Engineering Technical Notes (CHETN: ACOE--WES)