ERM 447 Design Project12/12/12

Joseph Smith

Group 3

The design reach of Poplar Run is incised and confined. It is an unstable F stream with eroding banks and aggradation near its confluence with the Frankstown Branch. The stream has been straightened for years and livestock trample banks. There is little to no riparian vegetation to protect banks from erosion. Considering all the aforementioned issues, it is not surprising that a BEHI analysis done on the reach produced a “very high” overall erosion hazard. Additionally, an SVAP assessment was conducted that produced a score of 5.55, which is classified at “Poor”. As this is the worst category, the stream certainly merits restoration. The bank stability is rated 1/10 and is rated lowest of any category. To improve the bank stability, the bank slopes must be tapered and the riparian zone must be built up. The SVAP rating for riparian zone is rated 3/10 for the reach. Increasing the riparian buffer will increase the bank stability and improve two of the three lowest rated categories.

The restoration project objectives are to improve bank stability so erosion is reduced, improve access to the floodplain, create a stable stream that does not incise or aggrade, improve the riparian buffer, and improve habitat. We want to create a C stream with long term stability. An upstream reference reach has been chosen to base the design of the new stable stream. There is a historic barn and a home that we are limited by at the beginning of the design reach.

We chose to conduct a Priority 2 restoration on the confluence reach of Poplar Run. For a Priority 2 restoration, a new stream channel is constructed in the current stream bed. There is connection to a floodplain at bankfull height. The new channel will have natural meanders and the stream belt width will span almost the entire excavated channel. The existing channel is incised and confined with steep slopes. The banks will be excavated and sloped. The excavated material will be used to fill the old channel. After the historic barn, we have enough lateral space available on both sides of the stream to open the floodplain and increase the sinuosity. The excavation required for a Priority 2 restoration will destroy the existing vegetation. Since the current stream has very little riparian vegetation, the damage will not be significant. A priority 2 restoration will reduce the bank angle and allow for riparian vegetation in the floodplain, therefore improving the SVAP assessment.

The Table II summary of characterization data was completed for the confluence (design) reach and the reference reach. Table II shows that the sinuosity of the confluence reach is less than the sinuosity of the reference reach. It is interesting to note that the slope of the reference reach is higher than the confluence reach. The valley slope of the reference reach is higher, making the stream slope higher although the sinuosity is higher. We can see from Table II that the reference reach has larger particles than the confluence reach. This is important to note because the reference reach will be able to handle a higher shear. The regional curve values are average values, so the accuracy is not exact. There are many outlying streams that were averaged to find the equation for regional curves.

Since Poplar Run has been straightened over the years, we wanted to ensure that we had proper sinuosity in the stream. The aerial photograph reveals the stream’s historic meandering bed, so we attempted to give the stream a natural meander. To give the stream proper sinuosity, we were careful to design the correct stream length.

Wyatt Stoup designed the aerial photograph sketch using ArcMap 10.1. Using the most recent photo from the reach, taken from the Pennsylvania Spatial Data Access (PASDA), he was able to draw the new meandering stream. This is where slope and sinuosity were important. Wyatt had to continuously measure and adjust the stream to create the proper length of stream so the parameters were true.

The aerial photograph also includes the in-stream structures. To stabilize banks, we added vanes at the newly established meanders. The vanes are designed to be one third of the bankfull width and constructed at a 20 degree departure angle. They will have a five percent slope from the stream bank to the stream bed. The first vane in each series of vanes will be a J-hook vane. J-hook vanes will slow the stream velocity at the point of curvature. The subsequent vanes on each bend will be straight because continuously lowering the velocity with J-hook vanes will lead to aggradation and instability. After the two downstream bends, mudsills will be inserted. They will be 40 feet long and will further protect the stream banks. Since mudsills have undercuts, trout habitat will be improved.

As previously mentioned, livestock trample banks when they enter the stream. We have chosen to insert fencing to ensure that livestock have access to the stream in one location. At the funnel point, we will line the banks and streambed with rip-rap so the cattle do not increase the sediment load as they use the stream. We are adding a riparian buffer that will measure 20 feet from the stream banks on both sides. This will stabilize the banks, reduce the sediment load, help funnel livestock to the crossing point, and provide trout habitat. We are introducing root wads and fish habitat structures to the stream to improve habitat. Habitat will be improved once the riparian vegetation has been given time to grow.

The proposed cross sections show the new bed with access to the floodplain in the old stream channel. The banks are sloped to reduce erosion and the stream is no longer confined and incised. The bankfull depth and width were based on the reference reach data in Table II. The new hydraulic radius is 1.93 compared to the old confluence reach hydraulic radius of 0.95. The reference reach hydraulic radius is 1.90. The longitudinal profile has been created to provide a stable stream. The slope has been modified to resemble the slope of the reference reach and the design slope that allows for sediment transport.

Pool Rifflex y Area x y Area

60 93.6 8.5 100 97.7 1570 91.9 21.5 110 94.7 30

80 91 28.5 120 94.7 14.35

90 90.5 9.3 127 96.6 1.65

96 93.6 130 97.7

total area

67.8 total area

61

Perimeter Perimeter10.14 310.04 2710.01

6.75

total wp 36.9499 total wp 30

Hydraulic RadiusHydraulic radius = A/wp 1.835 Hydraulic radius = A/wp 2.033Average hydraulic radius = 1.934

A stable stream must not incise or aggrade. A competency analysis will tell if the stream is stable or unstable. To is the shear stress at the bottom of the stream. It is calculated by To=yRS=(62.4)*(.95)*(.0059) = .349 lbs/ft^2, where the stream slope equals 0.0059 and the hydraulic radius equals 0.95. We chose to use the Rosgen and Leopold, Wolman, and Miller methods to calculate Tc. Using a D84 value of 97.73 mm and a D50 value of 43.34 mm, the Rosgen method was calculated by τc=0.00108Di1.36=(0.00108)*(97.73^1.36)=0.549 lbs/ft^2. The LWM method was calculated by τc=0.0152Di0.96=(0.0152)*(97.73^0.96)= 1.24 lbs/ft^2. Looking at the Table II shear stress value, we can see that the shear stress cannot move the D84 particles in the stream. These particles aggrade because they cannot be transported downstream.

The LWM method gave a result of .567 for the Tc to move the D50 particles. Using this and the reference reach hydraulic radius, we calculated the a new stream slope of 0.00478. From here, we could calculate a sinuosity that would move the D50 particles and a new stream length to move the D50 particles. The results from the calculations were a 1.32 sinuosity and a length of 1747 feet. The stream

was designed to match these numbers. Our stream design will still aggrade D84 particles. To avoid this, the slope of the stream must be steepened. It is not possible to steepen the slope for the design reach so that it will move the D84 particles. The stream will transport D50 particles.

Variable Confluence Reach Reference ReachUSGS Leopold Clapsaddle/Dill

Stream Type F CDrainage Area (mi^2) 17.41 15

Bankfull Width (ft) 44.7 29.3 49.4 44 46Bankfull Mean Depth (ft) 2 2.4 2.14 3.2 2.4

Width/Depth Ratio 65.65 16.86Bankfull Cross-Sectional Area (ft^2) 46 61.15 104.2 140 110

Wetted Perimeter (ft) 48.3 32.1Bankfull Mean Velocity (ft/s) 4.98 6.73

Hydraulic Radius 0.952 1.905u* 0.425 0.705

u/u* 5.506 6.148u 2.342 4.333

Bankfull Discharge (cfs) 107.735 264.988 452.1Bankfull Maximum Depth (ft) 2.17 1.96

Ratio of Bkf Max Depth to Bkf Mean Depth 1.085 0.817Width of Flood Prone Area (ft) 125 150

Entrenchment Ratio 2.796 5.119Meander Length (ft) 392.68 1377

Ratio of Meander Length to Bankfull Width 8.785 46.997Radius of Curvature 85.9 918

Ratio of Radius of Curvature to Bankfull Width 1.92 31.33Belt Width (ft) 100.6 540

Meander Width Ratio 1.28 16.82Stream Length (ft) 1460 2575Valley Length (ft) 1325 2200

Sinuosity 1.1 1.17Valley Slope (ft/ft) 0.0063 0.016

Average Slope (ft/ft) 0.0059 0.0081Pool Slope (ft/ft) 0.25 0.00632

Ratio of Pool Slope to Average Slope 0.625 0.732Maximum Pool Depth (ft) 3.25 6

Ratio of Pool Depth to Average Bankfull Depth 1.86 1.71Pool Width (ft) 16.3 18

Ratio of Pool Width to Bankfull Width 0.38 0.514Pool-to-pool Spacing (ft) 297.5 205

Ratio of pool-to-pool spacing to Bkf Width 7.028 5.857

D16 5.15 15.94D35 26.54 49.93D50 43.34 97.25D84 97.73 150.57D95 120.6 167.37D100 131 175

Particle Size (mm)

Regional CurveTable II Summary of Characterization Data