August 2021

Beaver Dam Destruction -- August 10, 2021

Ritch Seifert noticed two workers in the beaver pond. He has a good view of this pond from his deck. He notified me and this is a photo that I took from Ritch's deck.

These workers came from the large estate that is on the south side of the wetlands. Because of beaver dams the water level has risen and this interferes with their private lake.

It appears that they have decided to solve this problem by going into the THPRD land and installing a device that allows water to pass thru the beaver dam in such a way that the beavers are not able to stop the flow of water.

Here is a diagram of the device they installed.

Beavers build where they notice running water. This device allows water to go right thru the beaver dam without making the noise of running water. The beavers can build on the dam all they want but water continues to go past the dam as if the dam were not there.

The next day I took this drone photo of the beaver dam. It shows the arrangement of the device used to get water past the beaver dam. Water flows from right to left. The beaver dam is hard to see in this photo. I have labeled it in black.

Water enters the intake device, passes thru the black plastic pipe that goes under the beaver dam and exits some distance past the beaver dam.

At the time of this photo the water level had dropped by about a foot from the level of the previous day.

Why This Matters

We can be happy for the people in the estate. The water level in their private lake will now drop to the level that they desire.

But adjusting the water level affects more than just their private lake. This change in water level will dry up the wetlands that has formed over the last two years. This can best be explained with pictures.

The image on the right was taken around 2018. At the top are our Townhomes. The private lake is the half circular lake on the right. The largest part of this image is a pasture that was once used for horses. In this summer photo the pasture is brown consisting mostly of dry grass.

In 2019 the water level in Bronson Creek became high enough, due to beaver dams, that water started flowing thru this pasture. This is visible in the photo on the right which I took using a drone in March of 2021. The photo shows water running thru the field. This water has transformed the field into a wetland. It has become lush with cattails, sedges and aquatic plants. It now supports many more animals, birds and plants that it did when it was a pasture.

But now that the water level has dropped, water has stopped flowing into the field. The field will dry up. The aquatic plants will die. The area will transition back to a dry pasture.

The action taken by the people in the estate appears to be an act of selfish vandalism. They have made significant changes to land that they do not own for their personal enjoyment.

Wetland Plants -- July 27, 2021

Tansy ragwort (Jacobaea vulgaris). The flowers can be very beautiful but the plant smells bad. Another common name is stinking willie.

This plant is an official Oregon Noxious Weed and is a B and T listed plant. B Listed Weeds are of economic importance and regionally abundant. T Listed Weeds are species that are selected for prevention and control by the Noxious Weed Control Program.

Toshio Sakuma and I have removed about 100 pounds of these plants from the wetlands. We physically removed the plants, put them in plastic garbage bags and placed these bags in the garbage. We did this before the flowers turned to seeds.

Portions of the wetland area are difficult to access. Many of these plant were found growing in brush and wooded areas. After our removal effort I did a search and was only able to find two plants.

Orange Jewelweed (Impatiens capensis).

This grows next to water in areas that are damp.

As water levels fall portions of the stream start to dry up. The mud shrinks and cracks form. Even in areas that appear to be just soil many small plants grow. Recently, there has become an awareness that large numbers of microorganism live in rocks, deep in the earth crust. Life proceeds very slowly in rocks.

In the small amount of water left in the stream thru the wetlands small fish blend in to the color of the streambed. Their presence is given away by their moving shadows. Can you find the fish above the shadows?

Here are the delicate flowers of American Speedwell (Veronica americana), a plant that only grows in wet and swampy areas.

Nodding Beggarticks (Bidens cernua) are a late summer plant that grows in water or mud. I'm taking this photo from a distance to keep water out of my boots.

Broad-leaf Cattail (Typha latifolia). Moving thru the wetlands has become difficult. In many places I have to "swim" thru the grass, sedge, cattails and other plants that sometimes grow more than six feet tall. Although we might prefer a path the plants do provide excellent places for animals and birds to live.

Two views of Fringed Willowherb (Epilobium ciliatum).

Seeds are developing in the long pods.

Bittersweet Nightshade (Solanum dulcamara). This European import has spread across America. It is a close relative of potatoes and tomatoes.

Water Pennywort (Hydrocotyle ranunculoides) with circular leaves grows in water. On the surface of the water is Duckweed (possibly Lemna minor), one of the smallest plants.

This image shows a cross section of the new wetlands. A) Nodding Beggarticks (Bidens cernua). B) Soft Rush (Juncus effusus). The brown color is the flowering part of the rush. C) Pacific Willow (Salix lasiandra). This area has been planted with many willows by Clean Water Services. D) Cattails. F) Unidentified tree planted by Clean Water Services.

It will be interesting to see how many of these plants survive after having their water source removed.

So far, the Do Not Mow sign has been working. The few people who walk along our rock wall have formed a trail thru the grass and weeds. I have been removing some of the weeds and crews from Clean Water Services have also helped. I do need to trim some trees with lower branches that start to block the path. By not mowing along the rock wall I hope that this encourages the idea that this area is special in that it is not primarily being maintained for people.

Giant Hedgenettle (Stachys cooleyae). This plant is hidden in a thicket near the creek. It took two years to discovered it.

Trees have been dying at the intersection of Bethany and West Union. Is this because the water level has been rising? What is going on?

If you are waiting for a green light at the intersection of Bethany and West Union, look to the North-East and you can see a pond of water with dead snags, evidence that once trees grew here. One day I noticed the water and the dead snags and wondered how so much water had previously escaped my attention. Had this just happened? What will happen in the future? Since that time I occasionally notice the lake but I have lacked the motivation to explore the area and do the research that might shed light on why there are dead snags.

Recently I have discovered that other people are also curious about this lake and the dead snags. So I decided to takes some photos. Come with me on this expedition. What will we find?

While walking along Bethany Boulevard we see the entrance to the culvert where Bronson Creek goes under Bethany Boulevard. Water has left marks on the culvert showing that the water level is lower now that at some past times. This makes sense because we are in the dry part of the year in a very dry year.

As we get closer to the intersection, thru the brush we see a lake and some snags. We also see fallen trees. The dead trees that we see have no bark, an indication that they have been dead for some time. It is possible to determine when these trees died by looking at the tree rings. When trees die they stop adding rings. Nearby trees that are alive will have continued adding rings. By comparing cores taken from dead and alive trees the time of death can be determined to within a year or two. I don't have the tools, the skill and the motivation to do tree ring analysis.

We can now see the south shore of this lake. In the background are Douglas fir trees that are alive. They have bark. In the foreground are dead snags without bark. The snags appear to be weathered. It is hard to say how long they have been dead but they do not appear to have died recently. In this photo there are no trees that have recently died.

This photo was taken from the south shore of the lake. In the background we see the snags that are shown in the photo to the left. In the foreground are Douglas fir trees that have died. At some point in time the trees became infected with fungus. The top of the tree blew off because the tree was rotten. Woodpecker holes are visible. The fungus may have started after the tree "drowned" or it may have started after water weakened the tree.

This panorama was taken from the south shore. West Union is behind us and we see Bethany Boulevard on the left. The deepest portion of this lake is probably near Bethany Boulevard. As we go to the right the lake becomes shallow and eventually peters out. This makes sense because Bronson Creek flows from the right to the left, crossing under Bethany Boulevard as it goes downstream. However, there is no culvert along this portion of Bethany Boulevard so the water can't go directly downstream.

This map shows the area around our wetlands. The purple arrow points to the lake with the snags. The base maps is a current Google terrain map. On top of this I have superimposed a 1940 road map. The red lines show where roads were added in about 1995.

The purple arrow also shows the direction that water will flow. That is the direction that Bronson Creek is flowing. Bronson Creek, on the map, is shown passing close to Aberdeen Drive. It is in this position because the creek is actually a drainage ditch necessary to keep the water out of the pasture. Bethany Boulevard makes a great dam, holding back the water. Water that ends up near the intersection of Bethany Boulevard and West Union must then flow slightly uphill to get to the culvert. We can be fairly certain that the lake was created in about 1995 when Bethany Boulevard was built. The dead trees are consistent with the theory that the lake formed in about 1995.

Another way to tell if the water levels are rising is to look at photos of the water level taken at different times. This photo was taken in October of 2019. We can compare it to the photo that I took today (August, 13, 2021) which you can see about 6 photo up. The water level is now lower in 2021 than it was in 2019. Of course, the difference that we see is a seasonal difference. The water level in this photo is higher because the fall rains have started when this photo was taken.

I have not found earlier photos of this culvert.

On my way home I went over to the Civic Townhomes and observed the outlet side of the culvert. I doubt that there is an obstruction in the culvert. The water level on the upstream side of the culvert appears to be the same as the water level in Bronson Creek over at the Civic Townhomes side. I presume that the water level at the Civic Townhomes side is set by a beaver dam that is further down Bronson Creek. At this point my interest in this project started to diminish. A possible project for the future would be to look for that beaver dam, possibly by using a drone because walking along the creek seemed impassable.

I am unable to find evidence that the water level in this lake has changed since the lake was created in around 1995. It seem likely that the water level has risen a modest amount because of beaver dams that are further downstream.

Air Photos of Bethany & West Union

1998 -- No flooding observed in area to the right of the intersection. Images from https://wcgis1.co.washington.or.us/Html5Viewer/index.html?viewer=Intermap

2008 -- The area to the right of the intersection is flooded. Trees are dead. A small pond can be seen on the left side of the intersection.

2012 -- It does not look like there is standing water.

2016 -- No standing water. Maybe some new trees.

2019 -- A small pond is visible. Snags are visible around the pond.

2022 -- The pond is much larger. Water is entering the pond from the East.

I found that walking in the Douglas fir area between the lake and West Union was interesting. I had walked in this area a couple years ago and found the walk to be difficult because of the scattered blackberry bushes. It is still difficult. It looked to me like this area is a place that people just avoid. I decided to not touch any of the trees for fear that a branch may fall or even the whole tree could come down. Creeping blackberries caught my feet making it easy to trip. The ground was uneven. But I was surprised to see the following two plants:

A mature Tall Oregon Grape (Berberis aquifolium). There are Oregon Grape plants in our wetlands but they have been planted by Clean Water Services. It was nice to see Oregon Grape that appears to be natural. Perhaps we have no natural Oregon Grape because we lack a Douglas fir forest.