Bridges and streamwork

[JeffP]

I had posted a while back about 2 "newer"bridges on Middle Creek and how the pools they created were so much poorer than the older ones. So I was on lower Middle on Middle Creek Road down from the Church of the Brethern. The hole there was great. The new bridge actually had concrete structures and stone designed to channel the water more. In addition, there was significant stream work done upstream of the bridge as well.

So my question is whether you think this work was done specifically for fish. Who paid for it if it is?? If its not specifically for fish or more expensive, then Clay Township needs to serious talk with Warwick Township about their bridges.

 

[JeffP]

I wanted to note that the concrete structures were not part on the bridge itself.

 

[lycoflyfisher]

Was it a bridge or box culvert? Box culverts in most cases are required to have baffle structures to help maintain substrate in the bottom of the structure to allow for more natural stream channel functions and improve fish passage. More recent designs center the flow to provide a low flow channel.

In some cases the road owner or a local conservation group installs "habitat" structures during bridge replacement. The purpose is often twofold: provide bank stabilization or deflect flow into the center of the structure while also improving aquatic habitat. This could be part of the bridge project and paid for by the road owner or funded by various grant opportunities.

 

[troutbert]

Please post pictures, it sounds very interesting.

Are these structures you discussed part of the bridge itself?

Or are they separate structures done as part of a stream improvement project?

At one of Coldwater Conferences some years ago, the topic of bridges effects on stream habitat was discussed. There was a great deal of interest, and some heated discussion, from the audience.

But it was discussed too briefly, unfortunately. It's a topic that needs much more exploration. The civil engineering folks and the fluvial geomorphology folks need to get together on this.

 

[salvelinusfontinalis]

Bridges should be a discussion during stream restorations.
My findings from the land of covered bridges is that if good water depth is under a bridge, so is a fish or 5.

 

[JeffP]

I'll try.

 

[JeffP]

Sorry as I am always embarrassed to ask. I have 2 jpg s I want to post. Sometimes I get lucky. What do I need to do to post. When I try to upload it disappears.

 

[troutbert]

One thing I've noticed is that streams are commonly incised upstream from bridges.

Even in state forests. Sometimes for a half mile or even more.

They should be able to design bridges so that they maintain a normal streambed grade level upstream from the bridges.

Any civil engineers in the house?

 

[Dave_W]

JeffP wrote:
Sorry as I am always embarrassed to ask. I have 2 jpg s I want to post. Sometimes I get lucky. What do I need to do to post. When I try to upload it disappears.

You must reduce the size of your jpg's so that they are under 150kb before they can upload to the site.

 

[JeffP]

How?

 

[salvelinus]

Read this post. Tells you how to do it on phone or PC.

 

[JeffP]

I am a tech lightweight. I'll give that a shot. So I have them on my Mac. When it says PC does that means a Mac won't work? So I was able to get my jpeg down in size by making it smaller and changing the resolution. But it still won't work. Here's what I did:
-hit reply
-hit choose file
-choose my photo
-hit upload

Where I hit choose file, my bridge jpeg disappears and goes back to saying to file selected.

My jpeg now is below where it says max file size id 300K.

The far left column says Remove and there is a little check box that is unchecked.

Do I check it or does that remove it?

When I hit submit it just doesn't load. It seems to be trying but doesn't go anywhere.

 

[JeffP]

This won't work.

 

[Mike]

These channel improvements beneath bridges and in box culverts in my experiences are pretty much the standard approach and have been for some years. In some cases and perhaps all the modern box culverts are installed below channel grade so that, as mentioned above, natural substrate covers the culvert floor.

 

[JeffP]

It worked! Now I won't be able to do it again for the stream work photo.

 

[CLSports]

I am a bridge designer.

The stream work was most likely done to minimize the impacts of flooding and prevent future erosion around the structure, but it is possible some extra money was allocated for stream work too if it was necessary. Difficult for me say without knowing the project.

 

[Swattie87]

That bridge and culvert discussion was really interesting. IIRC, it was a bit of a dichotomy. In short, fish passage (good for spawning, and fish seeking thermal refuge) and habitat (good for growing and sustaining populations) were a bit at odds with one another in terms of planning the replacement of these structures.

For easy fish passage, you don't want any significant drop or plunge to the structure. This generally means you won't have a significant pool (habitat) on the downstream side. A good plunge pool, while making nice physical habitat, can become a barrier to fish movement for spawning or thermal refuge.

My experience in terms of the bridge and culvert replacements I've seen recently (say last 10 years or so) is that the priority seems to be fish passage. I can count many bridges/culverts that used to have plunge pools beneath them, and were usually a nice place to catch a nice fish, that now have the water flowing through much more at a natural grade, and the resulting hole is now gone. Typically replaced by a shallow riffle.

I don't really know what's better for the fish...Ideally they need to be able to move AND have good habitat, but when it comes to road crossings it seems difficult to achieve both of these things at the same time. While I miss the chance to catch a nice fish in some of these culvert holes, I do imagine the displaced fish will be able to find other suitable habitat most of the time, and the ability of fish to move freely throughout the stream system is more important.

 

[CLSports]

Swattie,
That plunge pool is a scour hole. It occurs over time through many flood events and it is bad for the foundation of the bridge structure as is usually an indicator of improper stream flow. If the scour hole undermines the structure then it could cause failure of the structure or even a collapse. As we all know by now, human lives are important too.

Proper channel flow would allow for little scour. If there is scour then rip-rap is added to reduce the scour around the abutments or piers if they exist. It is all about flood and erosion control. Not creating good fishing holes.

 

[CLSports]

Jeff,

That picture looks like exactly what I was talking about. The wall and rip-rap inside are to prevent erosion around the structure. I imagine that is on the upstream side. There is probably significant flooding on that stream too based on the extent of the wall. It is also possible that adding too much rip-rap alone would channelize the stream too much and cause the floodwater to over-top the structure in flood models.

It is designed to protect the structure.

 

[JeffP]

I know older bridges often had a narrow concrete ledge you can walk on. The one on K-Ville Road on Middle Creek near our house used to. I'll have to check and get a couple pics of the newer bridge there on Mountain Spring Road. Then there are the double bridges like on lower Hammer. They seem to seldom have a decent pool.