What Happens When Our Lagoons Breach?—Marna Powell

On May 11, 2010 Frank Galusha wrote to me and asked, "Help me out, here if you can. Does this mean the fresh water has drained out and the lagoon is now filling up with saltwater to be gradually replaced as fresh water runs in? And what happens to the resident cutthroat in the mean time? Thanks, Frank"

First I have to tell you that I'm not a fish biologist, geologist, ocean scientist or any other "ologist" but I spend a whole lot of time outdoors in nature. I feel like being long-winded so grab a beer and get comfy while I answer your question. The real ologists should feel free to grab a beer and correct or interject my response.

A lagoon is brackish water, that's a mix of fresh and salt waters. Key features of a lagoon is a freshwater feeder source, such as a creek, and a bar of sand or reef separating the lagoon basin from the ocean. The sand "spit" may or may not always be above sea level as high tide may sometimes cover the sand bar or reef.

Here in our neck of the woods we have an anomaly in that we have so many lagoon areas in a short geographical space. The lagoon basins were formed as a result of plate tectonics pushing land up on the sides and creating a trough in the middle. If you were able to look at a very wide view of our coastline from the ocean you would see a series of ridges and troughs. Filling these troughs is Humboldt Bay, Big Lagoon, Dry Lagoon, Stone Lagoon, Freshwater Lagoon, and Lake Earl/Lake Tolowa, along with the estuaries of the Eel River, Mad River, Little River, Redwood Creek, Klamath River, Smith River and a few others. [ Digressing from your question #1: I have to add that humans have really screwed up some of these once fabulous fish habitats through dam diversions (Klamath and Eel Rivers), infilling (Dry Lagoon), road building (Freshwater Lagoon) and the levy (Redwood Creek). ] The lagoons and estuaries are extremely important habitats for salmonids and migratory shore birds. (I could really digress on these topics too!)

Back to our lagoons. From an aerial view you would see long spits of sand on the western sides of Humboldt Bay, our lagoons and Lake Earl/Lake Tolowa. It should also be noted that Lake Earl and Lake Tolowa are actually also a lagoon and not lakes and not even separate bodies of water either, and maybe that Freshwater Lagoon was once a lagoon but is now a man-made lake. Confused yet? So these long spits of sand are formed largely in part due to our near-shore currents which travel down the coast from the north to the south. This is called a south current as it goes in a southerly direction. (Digression #2: Note that wind and swell directions are given as the direction they come from rather than where they are going. So a north wind, north swell and a south current are all going in the same direction. Digression #3: Note too, that wind blowing over water is given a speed in terms of knots or nautical miles per hour, while wind blowing over land is given a speed in terms of miles per hour.) These south currents take sand coming from the mouths of rivers, especially the Klamath River and push the sand along our coast. Feeder creeks bring freshwater into the lagoons and the sand holds the water inside the basin.

Breaching is a natural, and generally welcome occurrence in our lagoons as it provides a nice mixing of salt and fresh waters and allows the steelhead trout to do their thing going out to sea, coming in to spawn, whooping it up and being fishie-wishies. It also takes all that old algae and junk out and cleans up the lagoon waters for us. (Digression # 4: The dog deaths at Big Lagoon in 2001 were a result of a massive bloom of one of the blue-green algae. Big Lagoon never breached the previous winter/spring and by summer the water was warm, not very salty and the water quality reminded me of Chinese egg flower soup. It also smelled like a stagnant lake.) In a normal year the lagoon will breach a couple of times. What causes breaching? The feeder creeks, rain, and snow melt fill the lagoon with fresh water. The basin gets very full. In the winter our coast has strong storms from the south often creating massive 25 to 30 foot swells. Our beaches are steep anyway but in the winter we also have downwelling (water on the surface is pushed down to the bottom of the ocean along the coast as a result of the south wind). The downwelling and big swells creating big waves literally take big chunks of our beaches and deposit them as sand bars just offshore (Digression # 5: Ever wonder why we have surfers here in the winter? Sand bars and reefs under water make nice surf waves. Now you know.) At the weakest point on the sand spit the combination of big swell at high tide and fresh rain water filling the lagoon to bulging just literally makes a crack in the sand at the "mouth" or breaching point. It starts as a rivulet a few inches wide and within the next couple of hours the sand just gets busted out by all that hydraulic force and the next thing you know what began as a calm flat body of water in the lagoon becomes a class V whitewater wave train moving at incredible speed out into the enormous crashing dumping ocean waves. (Digression # 6: I have several friends who are astounding white water kayakers featured in those videos boating REALLY BIG STUFF, and a couple of others who are pro surf kayakers, but I don't think any of them would think it survivable to go out what would start as a really fun big wave train and end up in the smashing dumping mess at the end. Just mentioning this in case anyone might think it would be fun to try kayaking this section as the lagoon is breaching.)

So that is how the lagoons are formed and how they breach but what now? Luckily, not all of the water leaves the lagoon when it breaches. Salt water comes in, especially at high tides and fresh water still flows from the east side down the creeks. At Big Lagoon the main feeder creek is Maple Creek. Some of the cutthroat trout will undoubtedly stay in the creek and in the lagoon areas that still have water. The edges of the lagoon are very wide and muddy today. Big Lagoon has breached four times this year (2010). Saturday, May 8 was the most recent breach and today is May 12. If we do not get much rain between now and summer then Big Lagoon could theoretically be a big muddy pit by August with a shallow pool in the middle. I think I was sweating this same scenario out in the spring of 2005 when we got several days of good rainfall in early June that filled Big Lagoon back up. We currently have a weak storm front moving in and something that may hit us from Alaska. If you know of a good Shaman who can do us a rain dance please pay some homage. The birds, fish and recreational enthusiasts, along with this kayak outfitter (and her organic garden) would truly appreciate a few rainy days.

Hope you enjoyed your beer.

May 29 2010 Update:

Here is a photo from Barry Thorpe, taken today at the breach site. Oops, still wide open!

Well, we got our wish and the garden is happy. The month of May has had more rainfall than anyone can recall. However, the mouth is still open at the Big Lagoon breach. Many people are asking why. It has been exactly three (3) weeks since the breach and with all that rain most thought it would fill back up for the summer. Again, I am not an Ologist but...normal conditions causing our lagoons to breach involve winter conditions: South wind, downwelling, BIG swell, plus mucho rain filling the inside. This breach was different. The lagoon was so full of water from so much late rain that it birst from the inside out. We are in our late spring/early summer seasonal wind and water patterns. Although we have had more rainfall than most May months EVER, the offshore conditions are currently normal summer patterns: southbound nearshore currents, upwelling (not downwelling) mellower swell and northwest winds (not south). The conditions that normally create the resealing effect at the sand spit are not in effect at the moment. Now we are left wondering if it will reseal for the summer and what effect it will have on invasive mudsnails. Here are pictures of the County Park Launch site normally and currently:

July 28, 2010 Update:

Here is a photo taken on June 28 at the breach site. That's Matt standing in the breach area. Big Lagoon stayed open for eight weeks before the breach area closed in.

I have never been so happy to be wrong! We all knew that the breach area would fill itself back in eventually but I could not imagine it would raise the water level enough this late in the season without a lot of rain. I am so very glad to report that we have been back at Big Lagoon with kayak rentals since July 1, 2010 and that the water has continued to rise and hold. Also, the water this summer is clean and clear.

As it turns out there are two factors keeping the water level up. The first is the main feeder creek, Maple Creek to the east. We had so much late snowpack and rainfall that the creek is still pumping out plenty of clear, cold fresh water. We can still paddle up past the second bridge and it is almost August. Amazing!

The other factor is that the breach area at the north end is so incredibly wide, being about the size of a football field that during the higher tides ocean water is literally dumping into the lagoon. I've watched the water level drop due to wind and sun evaporation then miraculously come up a foot a day during the new and full moon higher high tides (oh, I so want to digrees into the semi-diurnal tides we have here...). The north end actually has a bunch of jellyfish trapped in the lagoon. There are also a lot of crab and baitballs. The fishing has not been good this summer as there is so much natural food for them with all those bait fish. Have not heard of anyone catching and cutthroat or steelhead, whether it is up the creek, along the shore or from a boat. Freshwater regulations for Big Lagoon still apply even though it turned into an ocean.

So what we have now is a very healthy lagoon that is basically ocean water on the north and west sides, only slightly brackish at the south launch, brackish on the east side and fresh in the creek. It is fun to stick my hand in the water as I paddle along and feel the different temperatures of these waters and taste how salty they are in different parts of the lagoon (we're talking finger-dipping, NOT drinking!). The density layers are interesting in different spots as well.

(oh, forgive me, I HAVE to digress) Normally cold water is denser than cold water so cold water will form a density layer under the warmer water BUT salt water is denser than fresh water SO there are some interesting density anomolies that take place in parts of Big Lagoon under certain conditions. For instance, right now near the south launch at the County Park ramp there is cold fresh water coming into the lagoon. At that inlet area the salty ocean water is being heated by the sun in this shallow area and has gotten very warm. The fresh water coming in is forming a reverse layer on top of the warm water. If a lot of people are playing in the lagoon inlet then it gets all mixed up but otherwise check it out. Put your hand in it. As you reach slowly down notice that the top is cold, the middle is warm and the bottom is actually hot!

These foggy days of July find the water so much warmer than the air. You will stay comfortable while kayaking and swimming but find it cold when you get back to your car.

Enjoy!

Frank Galusha is an outdoor enthusiast who runs www.myoutdoorbuddy.com a great resource for other outdoor people.

Marna Powell is a kayak outfitter who wishes she had a beer.