This post was written by Emily Ramlow
After months of project planning and weeks of long days in the ﬁeld, a stream restoration project is ﬁnally complete. Our work however, is just beginning. Every new site then needs to be monitored to create a historic log of data that will continue for about ten years and help improve future project designs. I was freed from the oﬃce this month to go out in the ﬁeld for a few days and do some monitoring on past restoration project sites.
Aerial view of a point bar in the bend of the Batavia Kill at the restoration project site called Conine in Ashland - post Tropical Storm Irene.
An almost 12 foot high point bar at Conine post Tropical Storm Irene. SCA intern Lilly is standing in front of the point bar wearing a green shirt for a height comparison.
We were sampling point bars, which are areas of deposited sediment on the inside of a stream bend. In addition to water, streams move sediment ranging from small clay particles to sand. In large storms they are even able to move boulders. These point bars are good indicators of the streams ability to move sediment downstream. After Tropical Storm Irene, the force of the water moved many point bars or added more sediment to existing point bars. One of the sites we visited even had a point bar that was almost 12 feet tall!
Here I am at the Long Road restoration project site adding point bar sediment to bags which we will bring back to the oﬃce for further analysis.
Point bar at the restoration project site called Long Road (completed in 2009) in Lexington - post Tropical Storm Irene.
The point bar sampling process is easy on paper but as expected, rocks can be stubborn and make the work harder. I worked with my supervisor Abbe to locate the sites for sediment removal and then we got to digging. We would dig a hole to a depth that was twice the width of our two largest rocks. This was not as easy as it sounds as each shovel stroke was met with the hard resistance of a rock. The harsh scratching noise of shovel against rock was unpleasant and reminded me of nails on a chalkboard…the thought of it still makes me shiver. All of the collected sediment, from the size of my hand to the size of the tip of a pin, were added to our bags and brought back to the oﬃce for the second part of point bar sampling… the messy breakdown.
Delhi interns Natalie and Dustin add another bag of dry sediment to be separated by the sieve.
Delhi interns Natalie and Julie hose down the rocks at the top to make sure all of the ﬁne sediments make it to the bottom sieve.
The second half of point bar monitoring takes a long time since all of the sediment collected from the point bars needs to be put through a sieve with layers of decreasing sized holes. The largest pieces are trapped at the top while the ﬁner sediments like clay ﬂow through each level until they reach the bottom and smallest sieve. Water is used to clean each rock to insure that every ﬁne particle makes its way down until it can no longer go through the sieve’s holes. Each sieve tray is then weighed with sediment and without sediment. We do a little subtraction and are left with a total weight in pounds of speciﬁc sized sediment for each site. For example, the project site called Long Road in Lexington had 15 pounds of sediment that was greater than 90 mm (softball size), 3 pounds of sediment between the sizes 11.2 mm and 16mm (marble size), and almost 6 pounds of sediment as small as 0.5 mm (sewing needle size).
Here are a handful of the top sieve collections, the middle collections and the bottom collections. The ﬁrst image has our largest collected rock which weighed in at 16 pounds.
We often had to wait for water to drain out of the lower sieve sizes since it would get backed up when the water was unable to slip through clay blocked openings.
With the help of three interns from SUNY Delhi in New York, we were able to ﬁnish the analysis portion for two out of three project sites. The work was messy since we were dealing with a soil and water combination (often known as mud) but the mist from the hose was certainly appreciated on such a hot day. Overall, point bar monitoring is important because it gives us an idea of how much and what type of sediment, the stream is able to transport. Through that data, we can determine if there will be a problem of erosion or the opposite, sediment build up, both of which can have very negative impacts on human structures like roads, bridges and homes.
Some of the ﬁner sediment is weighed. It will then be dumped and the sieve weighed again to determine the weight of sediment alone.
Delhi Intern Natalie shakes the sieve to help ﬁlter the sediment as intern Julie rinses the rocks.
Delhi intern Dustin found this rock in our sieve with interesting patterns most likely from a shell.
I truly enjoyed this project and found it to be very interesting as I was able to see a bag full of mixed materials be separated into such a wide range of sizes. Then there was the realization that the data collected from the simple process of sieving can be very useful and informative in determining how healthy the stream is from a sediment transport standpoint.