Association of State Wetland Managers - Protecting the Nation's Wetlands.

The Compleat Wetlander: Watching Waves Work

By Jeanne Christie

This week I went to adult surf camp. Summer surfing camps for minors have sprung up all over the country in recent years; and with them, opportunities for adults as well.  My class package was all inclusive.  It came with a wetsuit, surf board, beach chairs, snacks, beverages, a celebration dinner and instructors.

Day 1 was great. By the end of the first lesson I was managing to catch a wave and ride in lying flat on the board exhilarated with this modest success.  What I didn’t realize was how much my achievement had to do with the conditions: Intervals of a few good waves coming in at 8 seconds apart and periods of quiet in between to get back out beyond the surf for another wave.

waves1Day 2 was a different story.  Waves were 5 seconds apart and they never let up.  Getting myself and the board through the surf was an ordeal every time.  I would eventually emerge breathless, battered and on the far side of the surf, but feeling exhausted every time I made it back out beyond the waves to try again.  I made little progress with improving my surfing skills, but I did gather an interesting set of bruises.

It seems a little obvious in retrospect, but at the time I couldn’t believe how much difference a change in wave interval made.  Then I started thinking about wetlands.  I knew that wetlands attenuate storm surges and prevent erosion.  I had read it and even added it to my own work listing wetland benefits for years.  I realize suddenly that I had never thought very deeply, until I was standing there like a rootless wetland plant getting pounded, about how wave attenuation actually worked.

surge1

So I did a little research.

The strength of the wave hitting the coast (wave energy) is what determines its erosive potential.  Bigger waves, mean more erosion potential.

The second big variable is what the wave runs into as it advances towards shore: a slowly sloping beach? a quick, steep sloping beach? a rock cliff?  a flat vegetated wetland?  a concrete bulkhead?  A combination of one or more of these? Wave refraction concentrates or disperses the energy of a wave in response to the surfaces it encounters as it advances toward the shore.

marsh3Wetlands disperse wave energy.  They are flat, often extensive areas, reaching inland from the shore.  During storms, the flat contour of the wetland disperses energy. In addition wetland vegetation provides a rough surface that further breaks apart wave energy.  Large, continuous wetlands do a superior job of providing this service.

In contrast hardened, vertical surfaces such as cliffs and manmade bulkheads and seawalls actually increase the energy of waves and thereby increase coastal erosion.  To understand this I often think about standing on a sandy beach as the waves wash over my feet very quickly.  My feet and legs are a hard surface compared to the sand. After a few waves wash over my feet, they start to sink slightly as the sand around it washes away faster than the sand that is not lying against my feet.

But don’t take my word for it. To test out these ideas, a trip to the coast, preferably a beach, is definitely in order.  Go swimming. Play in the surf. Maybe sign up for your own adult surfing lessons. Don’t forget, this is a work assignment. Study the action of the lighthouse2waves.  Plow through the surf under different conditions.  Check the beach and surrounding area for signs of erosion.

My week of learning to surf was a fabulous and humbling experience.  I’ve still got a long way to go, but so much to look forward to.  Surfing is a great metaphor for life.  It’s all about the journey, not the destination.

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