Sediment Transport Through Kelp, Rocks, and CurrentsKarsten Turrey, North Olympic Peninsula Skills Center Natural

Resources

Introduction:The physical characteristics of the Elwha Beaches are always changing. For years the Elwha Beaches have been eroding and reshaping themselves. With the removal of two dams on the Elwha River came huge amounts of sediment washing down onto the beaches surrounding it. Currents and waves in the Strait of Juan de Fuca wash ashore rocks with kelp attached to them, and for the past few years people have been studying these “kelp rocks” to see if they bring a substantial amount of sediment onshore and how much it impacts the shoreline. At Elwha, surveys are conducted with the help of Ian Miller, the University of Washington Sea Grant Coastal Hazard Specialist.

West Elwha East Elwha

Discussion:There does seem to be a recurring spike in number of kelp rocks found in the winter and spring time on the West Elwha Beach. I think that it will be very interesting to see if that trend remains in future years. This recurring spike of kelp rocks could be due to the life cycle of the kelp rocks, stormy weather seasons, stronger winter currents, or other factors. On the East Elwha on 11/3/2012 there was a spike in the number, but not volume of kelp rocks washing to shore. This is probably because there were just a lot of small rocks washing to shore. Hopefully now that we have baseline data, we will be able to see how trends change after dam removal.

What is a Kelp Rock?Kelp is any large, brown, cold-water seaweed. It is not small, green seaweed. It grows in length anywhere from 2 meters to over 30 meters along the Pacific Coast. A kelp rock is just a rock that has kelp growing off of it. The kelp is attached to the rock by the “holdfast” which is like a kelp plants roots. The kelp works like a sail, pulling the rock through the water from the current.

Kelp rocks found on the East and West Elwha Beaches.

Rocks per Meter on West Elwha

00.5

11.5

22.5

Rock Volume per Meter on West Elwha

0

500

1000

1500

2000

Vo

lum

e (

cm

3)

I thought this was really neat how both of these graphs show the same spikes on West Elwha. I really wish that we had years more of data to look at just because it would be helpful, more fun, and interesting.

Rocks per Meter on East Elwha

00.20.40.60.8

11.21.41.6

11

/3/2

01

1

12

/3/2

01

1

1/3

/20

12

2/3

/20

12

3/3

/20

12

4/3

/20

12

5/3

/20

12

6/3

/20

12

7/3

/20

12

8/3

/20

12

9/3

/20

12

10

/3/2

01

2

11

/3/2

01

2

12

/3/2

01

2

1/3

/20

13

2/3

/20

13

3/3

/20

13

4/3

/20

13

Rock Volume per Meter on East Elwha

0200400600800

10001200

11/3

/201

1

1/3/

2012

3/3/

2012

5/3/

2012

7/3/

2012

9/3/

2012

11/3

/201

2

1/3/

2013

3/3/

2013Vo

lum

e (c

m3)

In recent surveys we have found very few kelp rocks. There were piles and piles of small woody debris from removal of the dams which could have been covering up a lot of the kelp rocks.

This did not look like what I thought it would so I went back through the data and it all seemed to fit. Based on this data there has been less volume of sediment dragged to shore from kelp rocks recently than in the past.

Procedure:During a kelp rock survey a team of people comb the beach looking for rocks that have kelp attached to them. The group measures the size of the rock, gathers the GPS location, photographs the rock and kelp, and determines what type of kelp it is and its condition (old or fresh). On the Strait of Juan de Fuca there are a few beaches surveyed, the two in this poster are East and West Elwha.

E. Elwha Reach

W. Elwha Reach

Elwha River Mouth

Beaches