Visitor Submit by Willis Eschenbach
In my meand’ring peregrinations of the multiverse, I got here throughout the next a few bay up close to the northernwest nook of California.
Misplaced Coast Outpost Article
The article is stuffed with individuals hyperventilating concerning the imaginary results of a claimed three-foot (one meter) sea stage rise in “a number of many years”.
Riiight … not taking place.
I’ll admit, nonetheless, that their claims of a excessive charge of sea stage rise at Humboldt Bay shocked me. Sea ranges alongside a lot of the northern west coast of North America are small or unfavorable, due to the geological uplift of the land. I anticipated Humboldt can be the identical. As an alternative, once I went to the NOAA sea stage website I discovered the next. Eureka within the map under is town on the shores of Humboldt Bay.
So the article is appropriate in a single regard. Measured sea stage is certainly rising quick in Eureka … however curiously, the following two tide stations to the north, Crescent Metropolis California and Port Orford Oregon, present falling sea ranges.
Say what?
I used to be shocked as a result of the west coast of North America is consistently being wedged upwards by the Pacific tectonic plate. The Pacific plate is diving downwards beneath the North American plate as they collide. This forces your complete west coast up vertically over geological time.
And surprisingly, in lots of areas the speed of uplift of the land is larger than the speed of sea stage rise, resulting in all of the scenic cliffs you see in images of the North Coast. As proven on the map above, the 2 tide gauge stations nearest to Eureka (Humboldt Bay) are Crescent Metropolis, CA, the place the ocean stage is dropping, not rising however dropping, at -0.8 mm per yr; and Port Orford, Oregon, which is barely unfavorable however nonetheless dropping at -0.06 mm per yr.
So Humboldt Bay is an anomaly, with a sea stage rise of 5.0 mm per yr. What’s happening?
Now, in my luckily misspent youth, I crab-fished commercially one winter out of Humboldt Bay, freezing my fingers breaking apart frozen bait for the crab pots at 5 AM on the best way out by means of the doorway proven under. So I’ve some understanding of the native turf. Humboldt Bay is a kind of bay that’s uncommon on the west coast of the US however is quite common on the east coast. It consists of a protracted slender bay created by a protracted skinny pure sand barrier offshore from the mainland, within the type of lengthy sandspits and or sand barrier islands parallel to the mainland coast.
Humboldt is shaped by two such lengthy sand spits, imaginatively known as “North Spit” and … properly, you guessed it. The pure opening between them has been artificially prolonged by a seawall on the finish of every spit, as seen under.
Humboldt Bay, Bay Entrance and Metropolis Of Eureka, 40.1°N
Humboldt is a fearsome bay for fishermen, as a result of in the course of the yr an underwater sand bar kinds throughout the doorway. Which means that at sure considerably unpredictable states of wind and tide, you will get a sudden “sneaker wave” that breaks all the best way throughout the area between the seawalls, closing out your complete entrance with whitewater … ugly.
Or the wind can whip the waves up and it breaks continuously throughout your complete entrance, and the Coast Guard declares the doorway closed, and in case you’re outdoors, it’s a good distance and harmful method to the closest harbor. Solely the Coast Guard goes in or out then, and it’s not fairly.
(And as a person who has labored on the ocean as a business fisherman from Monterrey Bay to the Bering Sea, I have to take a second to thank the ladies and men of the US Coast Guard for placing their lives on the road and being a business fisherman’s greatest buddy in time of hazard. You of us have the profound appreciation of each business fisherman I do know.
… an essential digression, however a digression nonetheless … so now we return you to your frequently scheduled programming.)
To maintain the Humboldt Bay entrance open, it’s essential to dredge it out yearly. The dredged materials is ~ 90% sand, 10% silt.
And that brings up an fascinating query—the silt is coming from the rivers that feed Humboldt Bay. However the place is the limitless provide of sand coming from?
The reply is, a seashore on the west coast of the US is extra precisely described as a hesitation in a gradual river of sand flowing endlessly southwards. All of the sand virtually anyplace on the coast is consistently being moved south by the mixed motion of the prevailing currents, the seashore waves, and prevailing northwest winds. All of those are incessantly choosing up bits of sand and shifting them only a bit southward.
You possibly can see the shoreside ocean depths by shade within the aerial view above. And you may see that having the 2 synthetic seawalls has impeded the southward move of water and sand. The shallows prolong outwards in a circle across the mouth of the seawalled entrance to Humboldt Bay.
Now, in case you have been placing a tide gauge, would you set it out on the tip of 1 or the opposite of the shifting, shifting North and South sand spits … or would you set it over on the mainland facet of the bay?
Effectively, one assumes for legitimate historic causes, the tide gauge is definitely situated on the Coast Guard station on the fringe of the Samoa Dunes State Recreation Space on the North Spit, within the location proven each above and under.
However not on shore, after all. On a pier. Or to be extra correct, taking on a whole concrete pier. Per the station residence web page:
The bench marks are on the Coast Guard Base property. The tide gauge is on the east finish of the southern pier of two finger piers instantly east of the 3-story Coast Guard station constructing. Station Description: Devices are hanging within the loft of the Coast Guard Boat Home.
Right here’s a photograph and an overhead view. Seems to be like a mixture two-boat boathouse and tide gauge station.
Additional issues abound. Take a look at the nautical chart under.
The docks and buildings on the higher proper facet of the graphic above are the Coast Guard station and the placement of the NOAA tide gauge.
Within the chart above you’ll be able to see the impact of the north breakwater on the gradual southward-flowing river of sand. On the north facet, the sand has crammed within the nook between the north breakwater and North Spit. It has prolonged and grown the seashore outwards in that nook, and the shallows now prolong to the tip of the breakwater.
Sand on the transfer.
Subsequent, word the frequently dredged entrance channel proven in white. It extends properly into the bay. And it’s dredged proper as much as the sting of the Coast Guard docks to permit for the docking of huge vessels.
So: To evaluate the bidding:
• The NOAA tide gauge is situated, not on strong floor, not even on mainland floor, however on an offshore barrier spit manufactured from … sand.
• Its nearest neighbor is the Samoa Dunes State Recreation Space, which like North Spit generally is made solely of … sand.
• The tide gauge is sitting in a big constructing on large heavy concrete piers that stretch down into … sand.
• The world simply farther into the bay from the tide gauge is dredged yearly to take away … the sand.
• The native sand flows and the form of North Spit have been significantly impacted by the development of two giant offshore breakwaters, and by the annual dredging of the doorway channel.
And with that as prologue, are you shocked that the wildly anomalous sea stage report strongly means that the North Spit tide gauge is slowly sinking into … sand?
The excellent news is, apart from for the small cities of Fairhaven, Manila, and Samoa which have been foolishly constructed proper on North Spit, the Humboldt Bay sea stage disaster is canceled—sorry, no refunds for many who purchased tickets.
These small cities might or will not be sinking—in any case, the spits have been there a protracted, very long time. That signifies that traditionally, the sand continuously being faraway from the spit by wind and water has been changed by new sand moved onto the spit by wind and water from the ocean facet. So for these cities, possible no quick risk.
The opposite excellent news is, I’m sensing a whiff of desperation from the group pushing the “EVERYONE PANIC, IN A DECADE WE’LL BE DEAD” line of patter … after 5 many years of failed serial doomcasting, appears extra of us are beginning to smart up.
And one of the best information? That will the truth that I’m nonetheless on the inexperienced facet of the grass, not the brown facet … and at 77 years previous I give thanks for that day-after-day.
My greatest to all, maintain your family and friends shut, seize the day, life is way too brief,
w.
My Ordinary Ask: While you remark, please quote the precise phrases you’re discussing. Makes issues clear.
Sea Stage Knowledge: North Spit, Crescent Metropolis, Port Orford
PS: Why doesn’t NOAA alter the info for the land subsidence? I believe it’s from a scarcity of information. In accordance with Sonel, the “Co-located GPS” is RedwoodsCCCN2004 … which is method down on the south finish of the Bay and never situated on both of the spits. It reveals subsidence, however solely at -0.85 mm/yr, clearly lower than that of the tide gauge at North Spit.
