Bear Cr Jumps Into Road During Flood

[geebee]

Tups wrote:
My gut tells me that V-weirs and J-Hooks favor brown trout (BT) over brook trout (ST). These structures are designed to create deep scour holes on the downstream side. It is my experience that BT are much more dependent upon deep holes than are ST. Now that the weirs and jhooks are gone, the BT no longer have such a habitat-based advantage.

i'd agree with that - BT like deep holes for cover, whereas ST will ise anything for cover.

 

[Chaz]

Tups wrote:
TB: In your opinion, from an ecological perspective, is stream avulsion good, bad or indifferent?

I don't know what TB thinks, but it isn't good for the road or the people that depend on the road. On the other hand, back in the late 60' and 70's the state took it upon itself, to straighten a lot of roads out and minimizing the number of bridges along streams. In the process they also channelized streams to help accomplish the straightening of roads.
This straightening may have contributed to problems during subsequent floods, including the Irene/Lee floods. I myself feel stream avulsions are probably good for the streams, if the streams move back to their former channel, but only if then left alone by the dopes that think streams should be straight and channelized.

 

[Tups]

Chaz: I've never been to BB Creek, but viewing Google Earth it appears that the Big Bear Creek valley is largely undeveloped. The Big Bear Creek Sportsman's Club and one other residence may be the only people served by Dunwoody Road. So yes, the washout of Dunwoody Rd affected those folks. But the road has been replaced in situ. In this case, and at the location where the avulsion occurred, Dunwoody Road is located in perhaps the best possible place; at the very edge of the valley.

Agreed, channelization for road work or flood control or any other reason is rarely a good thing. It oftentimes creates more problems than it solves.

But I am also wondering if stream restoration projects don't often create their own set of ecological and hydrological problems as well. I've seen quite a few failed ecological-based stream restoration projects. Big Bear Creek is a very good example of such a failure and should be studied carefully by restoration advocates (of which I am one).

 

[Maurice]

I have never seen the word avulsion used so many times in my life...I feel dirty.

Regarding the avulsion. I am not sure whether the stream was straightened when the road was built or not. Nor am I aware of how much use the road had prior to the avulsion. So I am speculating here but it seems to me that if the crik took the road for a few hundred feet and the road won;t be missed that much, leave it be and address the stabilization issues.

If however the road was necessary for local residents. Put the stream back and build the road at a higher elevation to prevent future infrastructure disruptions.

The trouts will make their home where ever you direct them.

 

[troutbert]

Tups wrote:
TB: In your opinion, from an ecological perspective, is stream avulsion good, bad or indifferent?

Avulsions are a normal part of the system. And good for trout habitat, and other creatures and plants, not just in the stream, but the whole way across the stream / floodplain system.

But if you have a road, or other developments such as buildings, in the floodplain, then of course you have a conflict.

During a flood, the stream jumps into the road grade, and you have a real mess, as seen in the video.

If you look at the topo map of Bear Creek, you will see that a stretch of the road and stream are both there in the floodplain, at about the same elevation.

Probably the best solution there is to relocate the road out of the floodplain, and put it on the adjacent hillslope.

As you drive around in forested areas, notice where the roads are located. Some are located right down in the floodplain, so they get flooded. Frequently.

But you'll also see that many of the roads that parallel streams have long sections that are NOT in the floodplain. But instead located on cut-and-fills in the hillslope. So, they never flood.

Many of these roads go up and down, with sections down in the floodplain, then going back up on the hillslopes.

With many of these roads, I think they could connect the sections that are already on the hillslopes, and get rid of as much road mileage in the floodplains as possible.

 

[Tups]

Maurice: "Avulsion" is not a dirty word! Based on Google Earth and the PGC Mapper, it appears that before the storm the stream flowed through the center of the valley. However, the pre-storm aerial indicates an old, abandoned (orthofluvial) channel located along the northern edge of the valley. Dunwoody Road is also located along this northern edge of the valley. The stream avulsed back into its old channel taking about 1500 LF of road with it. The road could theoretically be moved to a higher elevation, but the valley wall on the north side is very steep and likely could not be done without great expense. I would be opposed to returning the stream to its pre-flood channel.

 

[troutbert]

Maurice wrote:
I have never seen the word avulsion used so many times in my life...I feel dirty.

Avulsion revulsion??!!

 

[troutbert]

Tups wrote:
Chaz: I've never been to BB Creek, but viewing Google Earth it appears that the Big Bear Creek valley is largely undeveloped. The Big Bear Creek Sportsman's Club and one other residence may be the only people served by Dunwoody Road. So yes, the washout of Dunwoody Rd affected those folks. But the road has been replaced in situ. In this case, and at the location where the avulsion occurred, Dunwoody Road is located in perhaps the best possible place; at the very edge of the valley.

There is another route into the Dunwoody Camp, i.e. coming in "from the top."

They could abandon the section of road that is there in the floodplain that's causing the problems.

 

[Maurice]

Tups wrote:
Maurice: "Avulsion" is not a dirty word! Based on Google Earth and the PGC Mapper, it appears that before the storm the stream flowed through the center of the valley. However, the pre-storm aerial indicates an old, abandoned (orthofluvial) channel located along the northern edge of the valley. Dunwoody Road is also located along this northern edge of the valley. The stream avulsed back into its old channel taking about 1500 LF of road with it. The road could theoretically be moved to a higher elevation, but the valley wall on the north side is very steep and likely could not be done without great expense. I would be opposed to returning the stream to its pre-flood channel.

So when it jumps back...and it will. (Or do I need to say avulses) will it be OK to rebuild the road?

 

[Tups]

As I said, the road has already been re-built, so that's no longer an issue. Of course now the stream channel is located at the toe of the road slope and whoever is responsible for road maintenance (probably Plunkett Cr. Twp.) will have headaches in the future. Perhaps at some point the Twp will be faced with the political decision to close the road at the bottom and require entrance only from the top, but that is a very long drive, and long one-way-out roads are generally not desirable from an emergency stand-point.

Maurice: It is inevitable that the stream will some day avulse again at this location (perhaps back into its pre-2011 channel, perhaps creating an entirely new channel), but it may be 50 or 100 years before that occurs. Avulsion is a natural occurrence. My point is that artificially forcing the stream back into its pre-2011 channel is not a good idea from an ecological standpoint.

TB: Never mind avulsion revulsion, you started this!

It's a great topic btw.

 

[troutbert]

It is a good topic.

I hope we all receive checks for our consulting. :-o

 

[MKern]

Trout err you mentioned Greys Run in the OP. That stream, especially in the C&R section has several channels it jumps to occasionally. Granted they aren't the road but one time I fished there and two months later I came back only to find the stream was running a different path; one that had been used before.

While the fishing was poor in that stretch, it was neat to see. I kinda wish I saw it happen live. I can't make up my mind if it happens abruptly or slowly switches channels.

 

[troutbert]

MKern wrote:
Trout err you mentioned Greys Run in the OP. That stream, especially in the C&R section has several channels it jumps to occasionally. Granted they aren't the road but one time I fished there and two months later I came back only to find the stream was running a different path; one that had been used before.

While the fishing was poor in that stretch, it was neat to see. I kinda wish I saw it happen live. I can't make up my mind if it happens abruptly or slowly switches channels.

I think it usually happens abruptly, during floods. During a big flood, the water is flowing over the entire width of the floodplain.

In the stream channel, the water is flowing fast and deep and moving a lot of cobble and gravel. And also transporting big branches and even whole trees, root wads and all.

When some trees, branches (large woody debris) jam up in the channel, the water is slowed there, and the cobble and gravel drop out, filling the channel partially or even completely, right up level with the floodplain.

And the water gets shunted over and takes a different path, either enlarging an already existing relict channel or secondary channel (usually). Or sometimes just forming an entirely new channel.

Often there is some water going down the old channel still, so you have a "channel split" and have two channels flowing parallel to each other for a ways.

Then the channels typically rejoin further down. Often a pool forms where the two flows converge.

 

[Chaz]

Tups wrote:
Chaz: I've never been to BB Creek, but viewing Google Earth it appears that the Big Bear Creek valley is largely undeveloped. The Big Bear Creek Sportsman's Club and one other residence may be the only people served by Dunwoody Road. So yes, the washout of Dunwoody Rd affected those folks. But the road has been replaced in situ. In this case, and at the location where the avulsion occurred, Dunwoody Road is located in perhaps the best possible place; at the very edge of the valley.

Agreed, channelization for road work or flood control or any other reason is rarely a good thing. It oftentimes creates more problems than it solves.

But I am also wondering if stream restoration projects don't often create their own set of ecological and hydrological problems as well. I've seen quite a few failed ecological-based stream restoration projects. Big Bear Creek is a very good example of such a failure and should be studied carefully by restoration advocates (of which I am one).

I pretty much think that stream restoration work should be holistic, meaning the lowest impact possible.Nearly every in stream device fails at some point any it often is replaced, often with the thinking, it won't happen again. Faulty logic, because they all fail again if they've failed once. This is why I think the holistic approach works best, fence livestock off and plant trees and shrubs, let the trees and shrubs grow, and if they fall in the water, that's part of the program, leave it unless it threatens a bridge. If it threatens a house move the house, the house is in the flood plain.

 

[vern]

I'm going to take a closer look at the Big Bear Creek study and details, but for general consideration every stream shares common characteristics.
Course changes occur most frequently at alluvial points and in the low slope areas below. It's dynamic.

Hydrologic cycles have been altered in many watersheds for a variety of reasons (in many streams we now have many more caddis fly populations than mayflies because caddis can tolerate the changes in stream flow better).

As weather patterns have changed and extreme flooding has upended the bottom structure of many of our streams for the past 40 years, I suspect/hope we will be migrating toward considering stream channel structures built well back from the normal flow stream bank.

These devices would only be seen by the observer to be in effect during a flood.

 

[troutbert]

vern wrote:

I suspect/hope we will be migrating toward considering stream channel structures built well back from the normal flow stream bank.

These devices would only be seen by the observer to be in effect during a flood.

Could you tell us more about that? What sorts of devices are you referring to, and how would they function?

 

[Tups]

Vern: Like TB, I am having a hard time picturing the sort of structures you are describing. Habitat structures such as log and stone cross vanes and j-hooks are usually constructed within the channel, for obvious reasons. Bank and channel stabilization structures are typically constructed either across the channel (j-hooks, cross-vanes) or at the intersection of the bank and channel (deflectors, bendway weirs).

 

[vern]

Okay.

Picture some of the best, most stable fishing holes in a stream. Any stream.

They are going to be bridge holes, old dam abutment holes, projections of hard bedrock, etc. Large rock formations on the flood plain, such as glacially placed (not the lesser 20-year depositions).

If your study Rosgens' designs, he basically attempts to address flood stage flows with the largest rocks on the downstream high bank wings in order to do so.

Don't look at the stream flow as you see it on the day you are there. Look at the topography all around the site. That is what formed the flow. Build and place for flooding flows and you will get the pool basin formation you want using natural forces. After that, vegetation and instream structures, bank structures, stabilizers, etc. can be considered.

 

[vern]

I'm not talking about building an Egyptian pyramid, but look around, especially with the aerial mapping; all the examples are really all around us.

And try to remind people you love: Trees are not round balls of green on a stick. They grow toward the sun. They cannot do otherwise.

 

[Tups]

Vern: I gather you have not yet had a chance to read the Big Bear Creek post-restoration studies. I hope you get a cance to do so because the project is a good illustration of a Rosgen-style restoration project. I think it's fair to say that Dave Rosgen's purpose was to create a restoration system that attempts to balance stream flows and sediment movement during both high and low flows.

I'm not the sharpest hook in the box and I'm still trying to decide whether or not you favor the Rosgen system.