Sally Ormsby Park Watershed Study

Tuesday, October 22, 2019

More About the Trees of Sally Ormsby Park

Wednesday, October 9, 2019

Other watershed studies

Friday, October 4, 2019

Sunday, September 29, 2019

Urban Archery Program in Sally Ormsby Park

One cannot walk through Sally Ormsby Park without seeing the above image, declaring the archery hunting season within the park from September 7. 2019 to February 22, 2020. To some, these signs may come as a surprise, since the park lies in the middle of suburbia. However, an investigation of the website on the sign reveals further information about the program and its benefits.

Virginia’s Urban Archery Program began in 2002 as a means to control the increasing population of white-tail deer. Because man has eliminated the natural predators of white-tail deer (namely wolves, black bears and mountain lions) in urban Virginia, the white-tail deer population in many areas of the Commonwealth is estimated to be higher than it was when Europeans first settled in Jamestown. The result is that watersheds like Accotink Creek’s watershed in Sally Ormbsy Park are being over-browsed. Native shrubs and native herbaceous plants covering the forest floor are decimated by the dense deer population, causing erosion in many places where there is a lack of the multiple layers that a healthy forest habitat would have. This results in increased erosion and sedimentation in the creek. On the other hand, in some areas of the watershed, invasives like multi-flora rose and oriental bittersweet (both shunned by deer) have replaced the native plants, thereby decreasing the habitat value of the watershed. Also, an over-browsed forest is unable to regenerate itself.

The program has a humanitarian element as well. In urban and suburban areas that have an overpopulation of deer, many of the deer will starve to death in the winter when they have removed all the browse within their reach.

The Urban Archery Program has an excellent safety record and is strictly managed. Since archery accidents started being managed in 1959, there have been no injuries to bystanders in Virginia. The archers must obtain a permit that gives them a particular area where they may hunt and they may only hunt from 30 minutes before sunrise until 30 minutes after sunrise, from Monday through Saturday. They can only hunt from tree stands, which they must build themselves and they must use safety harnesses within the tree stands. If a shot misses a deer, because they are shooting from above at close range, the arrow will go downwards into the dirt.

The archer must field dress the deer out of sight of the public, leaving the entrails in the woods out of sight and preferably covered with earth or leaves. They must also retrieve any stray arrows from misses and report any injured deer that was not felled by the arrow.

In 2013 alone, 848 deer were removed from Fairfax County parks by archers, providing a significant decrease to the deer population. If you include archery hunting on private lands, the average number of deer killed each year is about 1500.

The Urban Archery Program in Sally Ormsby Park has been a win-win situation. It benefits the health of the watershed by decreasing over-browsing. It benefits the other native wildlife besides deer who need the cover and food provided by the forest shrub and forest floor layers. It benefits the archers, who are permitted to eat the venison from deer they have killed. And, it prevents many of the deer from having a slow, miserable death from winter starvation.

Thursday, September 26, 2019

Flooding of Accotink Creek and Flood Data from nearby Gauges

The National Oceanic and Atmospheric Association's National Weather Service maintains a website with current data measuring water levels at hundreds of river gauges around the country. The two closest gauges to Accotink Creek are on the Potomac River near Washington D.C. at Little Falls, MD and on the Potomac River in Georgetown (in Washington, DC). By going to the following web page https://water.weather.gov/ahps/ and selecting Virginia, you can then zoom in on Fairfax County and finally find Sally Ormsby Park with Accotink Creek running through it.

By Zooming out a bit, you find the two aforementioned gauges. Below is a map that shows the Little Falls gauge with its current water levels.

As you can see, the river is well below flood level now, largely because of the drought of the last 6 weeks, when the Greater Washington DC area has received very little rain. The next map shows the probability of floods at this gauge in the next month.

The above graph shows that the chances of reaching even lower flood levels during the next month are less than 10%.

I also examined the data on the Georgetown gauge location of the Potomac River. Below is a graph of river levels at that gauge.

What is noteworthy here is that the water levels of the Potomac in Georgetown rise and fall twice a day. This is undoubtedly because of tidal action on the river.

An additional piece of information on the website for Georgetown is that it shows inundation areas. Below is the photo from today.

You can see that there are no areas near the river that are currently inundated, but during a flood, they would be captured on this satellite image.

A search for recent flooding on Accotink Creek resulted in a Patch.com article about flooding on July 24, 2018. Warnings were sent out to subscribers of the Patch site that the creek had flooded Woodburn Road in Annandale (not far from Sally Ormsby Park) . Below is a photo of an abandoned car on Woodburn Road during that flood.

Steve Chenevey Fox5

The full story of this flood on Accotink Creek can be found at https://patch.com/virginia/annandale/moving-flood-waters-trap-car-annandale-photos .

Tuesday, September 24, 2019

Native trees in Sally Ormsby Park

This morning, I had a very pleasant walk through the Sally Ormsby Park watershed of Accotink Creek and inventoried and photographed the trees. Below are the species that I found. I am not 100% certain about the oaks (we have so many species of oaks in northern Virginia!), but did my best to identify them. The other species,, I am very familiar with and many can identify by the bark alone.

Eastern Sycamore, Plantanus occidentalis
American Beech, Fagus grandifolia
Red Maple, Acer rubrum
River Birch, Betula nigra
Box Elder, Acer negundo
Tulip Tree, Liriodendron tulipifera
Sweet Gum, Liquidambar styraciflua
American Hornbeam, Carpinus caroliniana
Black Cherry, Prunus serotina
White Oak, Quercus alba
Northern Red Oak, Quercus rubra
Southern Red Oak, Quercus falcata
Black Oak, Quercus velutina

Sunday, September 22, 2019

Topo map of watershed

Below is a topographic map of Sally Ormsby Park and Accotink Creek. The area within the red ink is the study area.

The sticky note at the top of the map denotes the elevation of 270 feet where Accotink Creek enters Sally Ormsby Park. The sticky note at the bottom of the map denotes the elevation of 260 feet where the creek leaves the park. So, there is only a 10 feet elevation loss in the park. About a 100 yards northwest on the Cross County Trail from eastern boundary of the park, there is a footbridge across the creek.