Chris' Bridge

This project consisted of a 40-foot single span bridge with ramps east of Tullo Road near Spring Run. The scouts built the forms for the bridge abutments. The Township Public Works Department excavated for the footings, and lifted the beams into place. The beams are 40 feet long, have a two-foot arch and weigh 1,500 pounds each. They were purchased from Enwood Structures of Louisville Kentucky who designed them to our specifications. Designed, built and shipped to us they cost about $1,450.00 each and there are three beams to support this six-foot wide bridge. This bridge uses the same beams that Tom's does but the picket handrails give a different appearance. The stream is much deeper at this point than any other bridge. During Hurricane Floyd the floodwaters went over the highest point of the bridge deck by about six inches leaving sticks and leaves caught on the bottom of the handrail. The east ramp was swept away, but as designed, the loss of the ramp did not damage the structure of the bridge. The total length with ramps is 62 Feet. Chris Navarrete and Troop 88 completed the bridge in August of 1997.

Scouts working on Chris’ Bridge

Musing Meanders and Pondering Pools
From this bridge you can learn a lot about how streams flow and change over time. Meanders are individual bends in a stream. Over time, they tend to move outward and downstream. Often the stream is deepest on the outside edge of the meander and the inside is a shallow bar of silt, sand, or gravel. This is because small currents, or eddys, erode the outside part of the bend and deposit material on the inside. Meanders dissipate the energy of the stream in this way. Any increase in flow during high frequency storms, such as a “two year storm” can accelerate the natural meander process by increasing the stream’s ability to erode.

Pools are deep, quiet areas created by erosion. Riffles, shallow, fast flowing areas of water, form from the deposition of material during storms. The presence of pools and riffles benefit insects, fish, and other creatures as water, aerated as it tumbles through the riffles, provides oxygen rich water to the pools where most of the stream life resides.

Look at all the stone deposited by floods since Floyd, and read the “walking the high ground” section. Notice the stones are all about the same size. They were sorted by the stream.

Meanders, Pools, & Riffles. From this bridge you can see examples of various type of stream flow.

A meander is an individual bend in the stream. They tend over time to move outward and downstream. Often the stream is at its deepest at the outside edge and the inside is a bar of silt, sand, or gravel sticking out from the bank at the point. This is because secondary currents, or eddies, erode the outside part of the bend and deposit material on the inside as a point bar. Streams with a single channel and many meanders are said to be sinuous.

Pools and riffles are related to meanders in that they form from the erosion and depositing of material. However, they are up and down changes in the stream bottom, rather than side-to-side changes in the banks. The pools are the deep quiet areas and riffles are the shallow fast flowing areas.

Pools are created by erosion and riffles by deposition during storms.

They tend to form at regular intervals spaced between five and seven times the width of the channel. They are better developed in streams in gravelly areas and where the slope is not very steep.

The pools and riffles combine to the benefit of insects, fish, and other creatures. The water is aerated as it tumbles through the riffles providing oxygen rich water to the pools where most of the stream life lives. The increased surface area caused by the shallow flow, splashing, and bubbles improve aeration. The more surface area and mixing, the more oxygen can get into the water.

The thalweg is line of maximum water depth and is where the water flows the fastest. This line often is an exaggeration of the stream’s meanders as it connects the deep areas at the outside of each bend. Where the thalweg crosses a riffle, the fastest flows along the brook may be found. In the pools the flow is much slower but the water in the thalweg still moves faster than the rest of the pool. If you wanted to float downstream fast, the thalweg is where you want to be.

The stream’s slope in this area is 0.002 feet per foot, which means it drops one foot for every five hundred feet of channel.

Tullo Farm Rd Access. Going uphill to the south from the east end of Chris' bridge is an access to Tullo Farm Road. It ends at a depressed curb about 100 yards before the cul-de-sac. Some street parking is available at this point.

This access trail is located on a six and a quarter acre lot acquired by the Township in 1987.