Flooding impacts on aquatic ecosystems

[afishinado]

Excellent article about the impact of floods on different type streams and during different times of year >

https://www.northcentralpa.com/life/outdoors/experts-flooding-impacts-on-aquatic-ecosystems-hinge-on-many-variables/article_b6d30c54-5ac8-11eb-a7a7-e79ebbd4a88d.html#utm_source=northcentralpa.com&utm_campaign=%2Fnewsletters%2Fheadlines%2F%3F-dc%3D1611313208&utm_medium=email&utm_content=read%20more

 

[Mike]

Paragraphs 5-8, inclusive, support my comments in the past regarding concerns about harvest or fall fishing as they pertain to the abundance of adult trout for spawning purposes. This was a flood, but the impacts on the adult population mirrored those feared by the anti-harvest/anti-fall fishing crowd. To repeat my past comment, the success of spawning and the number of young produced is seldom limited by the abundance of adults. Furthermore, the second storm and stream mentioned in the study supports my usual follow-up comment that production of young is seldom limited by adult abundance, which in that case there were many, but instead is limited by environmental factors.

This is an excellent article for anglers to contemplate as many excellent points are made about coldwater populations, warmwater populations, behavioral adaptations to stressors, compensatory mechanisms, and the concept of competition.

I would add one thing about small year classes among coldwater, coolwater, and warmwater species. Small year classes are usually followed by large year classes one or two years later, often one year later. Again, nature’s compensatory mechanisms at work.

Finally, it is always great to see a former Fisheries Management Area 6 staff member get some ink and show his stuff. Mr Lorantas has been the agency’s Warmwater Unit Leader in the Fisheries Management Division for many years. He spent the very early parts of his career in Fisheries Management regions in SW Pa, SE Pa, and Erie. His explanations in the article are succinct and right on target!

 

[lycoflyfisher]

I have mentioned the research referenced in this article that was conducted by Susquehanna University numerous times. The timing of flood events is a major variable on how long it takes a trout population to recover from a flood event. Also, in the 2011 event they observed streams with connectivity barriers did not rebound as quickly and in fact I believe some streams still showed reduced populations almost a decade after the first event.

Mr. Lorantas' quotes were good, but its rather interesting given the topic of the article that the author didn't get comments from the local Area Fisheries Manager or Coldwater Unit Leader since the bulk of the article is discussing trout reproduction in Coldwater streams.

 

[troutbert]

I'm glad that channelization was mentioned.

Because floods have always occurred.

In natural stream/floodplain systems, with complex habitat such as freely meandering streams, multiple channels, lots of large woody debris, with no separations of streams and their floodplains by berms, walls, road grades, logging railroad grades, legacy sediment, the stream systems are resilient.

The damage from floods is lessened by all those features. But most of our stream mileage has been highly altered. The amount of large woody debris is a small fraction of what it was originally. Stream channels have been straightened, moved, multiple channels consolidated into a single channel, and structures separate streams from their floodplains.

The result, as the article says, is the streams are now much like flumes. The water just roars down and scours everything out.

So, returning the stream/floodplain systems towards more complex habitats is what it's all about. And I think that should be emphasized in articles like this.

The article is interesting, but it doesn't summarize with: "What should be done."

 

[Mike]

Regarding general content, as a veteran of hundreds of interviews, writers are usually on a deadline and have limited column space. Additionally, they or their editors may dictate the topics covered and may limit or broaden the articles as they see fit. As a result, they may not get to interview exactly whom they want and they may expand the topic to cover other areas of interest, such as in this case the impacts on warmwater fish. They may not cover the future regarding particular topics because of limited column space.

 

[Maurice]

I disagree with Wilsons assertion that Flood events cause increased sedimentation and streambed being covered with silt. My experience is that a good scour event removes the silt veneer on the rocks and streambottom that accumulates during periods of normal rainfall and stream volume fluctuations.

Additionally, as demonstrated by streambank pin surveys conducted in the early 2000,s in our watershed headwater streams we found that a greater degree of bank erosion occurs during normal rainfall events cumulatively as opposed to over bankfull events.

I believe this phenomenon is established when the stream hits a extreme peak volume the water is silt laden and the water drops, clears and velocity is still great enough to flush and clean stream bottoms distributing the fines onto floodplains and in-bank point bars before returning to normal levels.

Conversely, repeated small stream rain events that repeatedly erode the toe of the slope cause greater sediment loads per volume with bank slumping and shorter time for receding water velocity to clean the stream bottom thus creating the silt veneer typically seen in low clear water after a period few rain events.

In summary; Repeated erosion at the toe of the slope has a greater impact on sedimentation than single extreme high water events.

 

[JimKennedy]

Mike is absouletly correct about journalists having deadline and space issues to deal with. In the case of John Zaktansky, however, his byline lists him as the Middle Susquehanna RiverKeeper. Typically this means the work is a guest column or a regular or occasional feature by someone in a community leadership role (such as river keeper). In these cases, the writer generally covers the topics desired and interviews the people he or she believes need to be interviewed. From the perspective of such writers, the deadline issue doesn't come into play. For articles published online, space issues aren't the problem they were when a page of newsprint had 126 column inches with approximately six lines of body type per inch. A newspaper page looks big, unless you've ever worked for a newspaper. The internet, by contrast, has unlimited space, and it doesn't matter how big you make the text.

As someone who spent 30 years writing for newspapers and editing copy from reporters and community folks, I can attest that the two things all published articles have in common are:

1-Everyone who reads it will believe he or she could have done a better, more complete and more accurate job and focused the article exactly the way it should have been focused in the first place. This is because everyone (including the writer) comes to every subject with a unique perspective. The more the reader knows about the topic, the more passionate he or she feels about the things that should have been added or presented differently. There's a great misconception that journalists have hidden agendas or are attempting to put a spin on things. The ones who do generally leave the news business (though in recent years, they've become opinion writers, often at the expense of actual news). Most news writers simply want to do a good job and tell it like it is. Necessarily, when they start out, they approach every new topic with a high level of naivety, and as they become experienced on a beat, they become rather expert (for example, I became "rather expert" on the subject of sewer systems and septic systems). I say that as I also point out that the writer in this case, while a journalist by training, is writing as a community member who is fairly well-informed on a particular issue. It's a subtle distinction to the casual reader, but one that is worth paying attention to.

2-Every article, news story or other work of non-fiction is inherently incomplete. The article made no mention of, for example, the history of forestation, starting with pre-colonial times, continuing through the horse-and-buggy era when the demand for pasture lands resulted in a lot of deforestation, and then through the modern reforestation efforts (which began in the early 1900s). Forest cover has a lot to do with flooding and how floods change over time, so you could argue that a deep dive on the history of timber cutting is in order. I'm still a writer by trade, and am subject to the demands of two mutually exclusive expectations: make it short and include all the important details. After a first draft, I'll often be told "Add all these things and make it a lot shorter."

News stories of this nature (there's no event that triggered it; rather it is a perspective piece on a local issue) are designed to bring people with a range of levels of interest in a subject up to speed. Ideally, it'll be interesting enough that someone who doesn't believe he or she has an interest will start reading and say, "Wow, I never knew any of that. This is more interesting than I expected." That's an ideal, though. Mostly it's just to shed some light on a subject of general interest and relative importance to the community.

Anyhow, the perspective of being a news source who is frequently interviewed is important. Mike's points about incompleteness and deadline pressures are well taken. I just wanted to round things out by adding the perspective of an interviewer and news business insider.

 

[k-bob]

As TB notes, the original linked article mentions how channeling may affect flood impacts on streams. Spend some time w "PA MAP 3.2 ft" lidar map at pasda, and many small and remote streams appear channeled and separated from larger floodplains... ex is little nescopeck east of nescopeck state park, but not unusual in PA. Channeling may be common but not sure it can be redressed now?

 

[k-bob]

https://maps.psiee.psu.edu/preview/map.ashx?layer=1247

 

[troutbert]

k-bob wrote:
As TB notes, the original linked article mentions how channeling may affect flood impacts on streams. Spend some time w "PA MAP 3.2 ft" lidar map at pasda, and many small and remote streams appear channeled and separated from larger floodplains... ex is little nescopeck east of nescopeck state park, but not unusual in PA. Channeling may be common but not sure it can be redressed now?

There are ways to redress channelization.

For example on Fields Run.

N 41.20451 W 77.95083

You can paste the lat/lons into AcmeMapper and look at the topo map.

The water quality of this stream is good and the watershed is nearly 100% forest and it's on state forest land.

But the trout population is low. The reason for that is poor physical habitat.

And the reason for that is the stream appears to be channelized and straightened and confined to one side of the floodplain and separated from the rest of the floodplain by an old road grade, which may have been a logging railroad grade back in the day.

Solution: Eliminate the old road grade by regrading. Plant trees on the exposed soil.

Once things are well re-vegetated, in 10 years or so, come back and do large woody debris additions.

The large woody debris will start to create pools and cover, provide grade control to reverse incision, create lateral movement increasing sinuosity, and development of multiple channels, all of which would lead to the stream being re-integrated with its entire floodplain.

 

[silverfox]

troutbert wrote:

k-bob wrote:
As TB notes, the original linked article mentions how channeling may affect flood impacts on streams. Spend some time w "PA MAP 3.2 ft" lidar map at pasda, and many small and remote streams appear channeled and separated from larger floodplains... ex is little nescopeck east of nescopeck state park, but not unusual in PA. Channeling may be common but not sure it can be redressed now?

There are ways to redress channelization.

For example on Fields Run.

N 41.20451 W 77.95083

You can paste the lat/lons into AcmeMapper and look at the topo map.

The water quality of this stream is good and the watershed is nearly 100% forest and it's on state forest land.

But the trout population is low. The reason for that is poor physical habitat.

And the reason for that is the stream appears to be channelized and straightened and confined to one side of the floodplain and separated from the rest of the floodplain by an old road grade, which may have been a logging railroad grade back in the day.

Solution: Eliminate the old road grade by regrading. Plant trees on the exposed soil.

Once things are well re-vegetated, in 10 years or so, come back and do large woody debris additions.

The large woody debris will start to create pools and cover, provide grade control to reverse incision, create lateral movement increasing sinuosity, and development of multiple channels, all of which would lead to the stream being re-integrated with its entire floodplain.

Pretty sure the population there is limited by the stream going completely dry some years AND due to its gradient and the impact of flooding/scouring. I've hiked fished it from mouth to the top several times and I don't know that I'd say habitat is a limiting factor. There's some incredible habitat in there.

I've always attributed fish size/population size to an event that seems to wipe out almost the entire population of a certain year class. It's not that it's lacking in numbers, but you can almost see the year classes stop at 2 or 3 depending on when you fish it. Tons of cookie-cutter fish of all the same size/year class. That indicates something is wiping out a year class, not stunting due to lack of habitat. i.e., early spring floods, anchor ice etc. in there will completely wipe out redds due to the gradient drop along it's course or the stream going completely dry wiping out one or a few year classes.

Also, certain sections of that canyon are so narrow that even if they regraded the old logging road grade down through there I don't see how that would have a huge impact. A lot of it is confined to a very narrow course whether the grade was there or not. Granted, down in a few areas it could spread out, but generally, in most of those places, the floodplain is accessible to the course. The road grade is on the high side and the lower areas are opposite and there's nothing preventing the course from spreading out into those low areas. I think the geology down in there plays a big role in channelization too.

That's my opinion on that particular stream. I also think if the WB wasn't so badly polluted down there from Moshannon Creek that it might function differently too.

 

[silverfox]

Mike wrote:
This was a flood, but the impacts on the adult population mirrored those feared by the anti-harvest/anti-fall fishing crowd.

I'm sure I'm included in this group. For what it's worth, my recent comments were about how staff seemed to be arguing IN FAVOR OF C&R regs for brown trout below STW's without any creel survey data/harvest data to suggest that C&R below STW's is necessary while arguing that C&R for brook trout is NOT necessary based on creel survey data/harvest data.

It's the double standard that bothers me more than the argument for/against C&R.

As I stated in the other thread, there's the public image of the regs that needs to be considered too. Does habitat, temperature, anchor ice, flooding, drought etc. play a bigger role than harvest? Yes. Without a question. Could harvest regs prevent further losses when combined with those issues in some places? Also yes. In my opinion.

 

[k-bob]

never been to fields run, but if it seems to have varying age classes of brookies, it is a heavily burgoon bedrock drainage, and thus may see acid spikes w released toxic aluminum when floods or snowmelts happen.

https://www.arcgis.com/home/item.html?id=dba8455c266b4b958b403959185ed97b

"Water samples from the Burgoon Sandstone Member of
the Pocono Formation were the most acidic. The median pH of
water samples from the Burgoon Sandstone Member was 5.9;
from the Mauch Chunk Formation, 6.6; from the Catskill Formation, 6.9, and from the Huntley Mountain Formation, 7.0."

https://pubs.usgs.gov/sir/2013/5085/support/sir2013-5085.pdf

acid / aluminum events might differentially affect brookies of various ages?... for ex think I recall higher mortality in smaller fish

https://dep.wv.gov/WWE/Programs/wqs/Documents/Triennial%20Review/May%2018%2C%202009/17156_DNR_Iron_Study_1.pdf

 

[k-bob]

acidity impact moderated by fish size:

"Brook trout respond to decreases in pH with decreased growth rate in all size classes, decreased survival rates of small fish, and decreased egg?to?larva survival rates."

https://esajournals.onlinelibrary.wiley.com/doi/abs/10.2307/2269561

 

[troutbert]

silverfox wrote:

Pretty sure the population there is limited by the stream going completely dry some years AND due to its gradient and the impact of flooding/scouring. I've hiked fished it from mouth to the top several times and I don't know that I'd say habitat is a limiting factor. There's some incredible habitat in there.

What did you see that you're describing as "incredible habitat?"

I'm wondering if different people have different ideas about what is good habitat.

Or if we were on the same stream.

I remember one short section that had some nice pools and cover formed by rocks. And that area had loads of brookies.

But the rest of the stream had very limited pools and cover.

 

[silverfox]

troutbert wrote:

silverfox wrote:

Pretty sure the population there is limited by the stream going completely dry some years AND due to its gradient and the impact of flooding/scouring. I've hiked fished it from mouth to the top several times and I don't know that I'd say habitat is a limiting factor. There's some incredible habitat in there.

What did you see that you're describing as "incredible habitat?"

I'm wondering if different people have different ideas about what is good habitat.

Or if we were on the same stream.

I remember one short section that had some nice pools and cover formed by rocks. And that area had loads of brookies.

But the rest of the stream had very limited pools and cover.

There are several large plunge pools way down in away from the campsites/cabins in the upper end. Some of that upper section is lacking in terms of habitat.

Further down in I found a fairly natural amount of LWD and what I'd call typical brookie habitat. I caught fish from top to bottom so maybe time of year played a role in what you saw? The last time I was in there was May 22nd 2020.

 

[troutbert]

Silverfox,

Thanks for the posts.

When I was there the water was pretty low, which is not the best situation to evaluate a stream.

 

[k-bob]

If you jump down to the thread on shavers fork in wv, right at the start the linked video mentions the released acidity that can be lethal to trout in a snowmelt. Later on in the video it mentions that smaller fish have higher mortality in these snow or flood events. Given the heavily burgoon bedrock geology of fields run, it may be subject to such an event. Cyclical populations, uneven age class representation could result.

 

[k-bob]

OP is about effects of catastrophic floods on trout varying by time of flood...May also be worth thinking of a flood type at lower water flow but with more acidity: snowmelt, which can cause acid spike in PA's many small headwater streams with low buffering bedrock drainages.

Quote below from exc pfbc survey report on small brookie streams that were wbtep, probably applies to fields run discussed this thread.

 

[mr7183]

Sorry to bump an old post. I am wondering if there are any good resources to learn about the impacts of floods on mayfly hatches.

I was talking with my dad about this and we were reminiscing about how the hatches (mostly March Brown and Sulfur) seemed better at our local streams (Fishing Creek / Huntington Creek near Benton) before the big floods in the late 00s / early 10s. Can large flooding events significantly impact mayflies? If so, how long does it take for them to recover?