The Value of Culvert Replacement
We all know one. An ugly, impractical beast that you just can’t imagine was purposefully constructed. At the same time, you know Mother Nature would never do one of her streams that dirty.
That’s right, today we’re talking culverts. The pipes, concrete boxes, and rebar that tunnel streams under roadways and railroads. The idea behind a culvert is simple: it needs to be strong enough to support the road above ground, and big enough to pass the water below ground. But, turns out, after 150 years in the business, humans are still trying to figure out the right balance between the two.
Some of the earliest design criteria for a culvert were published in 1853 in the 6th Edition of A Manual of the Principles and Practices of Roadmaking. Simply put, they recommended that culvert “size must be proportional to the greatest quantity of water which can ever be required to pass, and should be large enough to admit a boy to enter to clean them out.”
Really, we’re using “boy” as the unit of measure?
Today we might scoff at the inadequacy of those basic requirements for culvert design. But, for 1853, that simple recommendation was revolutionary. It also spurred rapid advancement of basic hydrologic theory because, at the time, there was no way to measure the “greatest quantity of water” that would pass through a culvert. We could guess, but flows are tricky- there’s drought and wet years, hurricanes, and heavy snows. So, some brilliant mathematicians worked out the numbers, and by the 1900s they found fairly simple equations that could estimate flood recurrence intervals and peak discharge. Crazy enough, these equations were so good that they still form the foundation of those calculations today.
But, something was still missing. We might know how much water passes past a point (otherwise known as stream discharge), but what’s the most efficient structure for facilitating that stream flow? It wasn’t really until the 1920-1950s where scientists started considering the position of the culvert in the stream. Should the culvert be completely submerged? Mostly out of water? What if the inlet is completely submerged, but the outlet not? Vice versa? Things get complicated fast. And, while we’re now better at designing culverts, we still aren’t 100% sure the answer to some of those questions.
Complicating matters is that oftentimes the most efficient way to transport water isn’t the most fish-friendly design. It turns out, fish are really finicky when it comes to culverts. They like a very set amount of flow, substrate sizes, and shade. If the culvert is too long they won’t pass completely through. If the water depth on either side is too deep or shallow, they won’t pass. Some species are more divas than others, but all have a very narrow window of conditions they are willing to tolerate.
Do you know how scientists found out that fish weren’t passing through culverts? The hard way. After decades of data collected on millions of culverts and hundreds of studies on fish swimming and jumping abilities, we have refined our understanding of what makes a culvert “passable” or not by fish. Unfortunately, when we started looking at culverts with a critical eye, we started realizing that many need to be replaced in order to achieve adequate fish passage. Replacing a culvert is no easy feat. It’s expensive, requires a lot of work hours, can be a huge hassle with traffic, and could also endanger fish populations in the stream. Making matters worse, a lot of culverts that need replacing aren’t even that old. The really poorly designed culverts- the ones that dangle feet off the stream bed, or are crumpling- may be a few decades old. But, many culverts that score low on the fish passage test are less than 10 years old. Before we start tearing down was is essentially brand new infrastructure, we better be sure that the end result will be restored fish passage, increased population connectivity, and overall increase to stream health.
That was part of the motivation behind a study that researchers from West Virginia University recently undertook. Simply put, they sought to determine whether culvert restoration will restore brook trout connectivity. Using genetics, they found that before culvert replacement populations below and above two culverts in West Virginia were structurally dissimilar. Otherwise, very few, if any, brook trout were swimming through the culvert and the populations above the culvert were genetically isolated (to read more on why genetic isolation can spell bad things for brook trout populations, click here). After culvert replacement, they found immediate evidence that fish were swimming upstream and that population connectivity had been restored. Success!
But, let’s not go tearing out all the culverts just yet. This was an obvious case where skilled engineers and biologists worked together and installed a culvert that was designed better than the one that was previously in place. But, sometimes it’s not that easy. Sometimes, what should be a great culvert still doesn’t result in great fish passage. And, a culvert that doesn’t seem so great by design is biologically functioning just fine. Biology is oftentimes more than a numbers game, and it’s worth reiterating that there’s no one solution to every problem. That’s what is making the science of culvert design frustrating and at times slow. There’s so many variables, and nature can be so unpredictable.
Further, even if we did know the perfect culvert design for every stream, there is also the question of whether populations really should be reconnected. If the isolated population has great genetic diversity, large size, and is seemingly healthy, then maybe it’s okay to place that stream low on the priority list for culvert replacement. Or, if downstream of an impassable culvert there is a thriving population of a nonnative species, maybe we should start considering whether we want to purposefully prevent fish passage.
That’s right, I said it. Go against everything I, and science, have ever told you and PURPOSEFULLY keep populations isolated. But, that’s a story for the next blog…
*Note: Content in this post is my own and may not reflect the opinion of the manuscripts' authors or the agencies they represent. I encourage you to read the manuscript, found here, so you can contribute to the discussion.
10/3/2018 11:35:49 am
One of our responsibilities while living is the fact that we should be an agent for environmental protection. We are the ones who live here, so we have the responsibility to keep it protected as long as we can. It’s just sad that there were several inventions that couldn’t handle the pressure. Instead of helping, they have caused more trouble and we are left with not knowing what to solve first. These culvert must be imprived so we can make use of it.
1/7/2020 12:31:57 am
A sporty looking hoverboard at a considerably cheaper price, the Swagway X1 has everything to impress your friends and family
7/4/2020 01:27:37 am
Thank you for simplifying the idea behind how a culvert works to support the road and also the water passing within it. I do think that culverts are an important part in construction in our country because we have so many streams. I would imagine that a contractor will want to make sure their culvert can support the road above while letting the water flow through the culverts without disruption.
5/6/2021 09:25:58 pm
I like that this post shared with us that culvert replacement is important. My brother mentioned he needs to have his culvert piping replacement. I will remind him to look at the pipes.
10/17/2022 06:03:07 am
Expect start project. Activity ability subject common lose.
12/26/2022 01:33:18 am
Great! you did well
1/16/2023 10:22:39 am
Excellent article. Very interesting to read. I really love to read such a nice article. Thanks! keep rocking.
2/19/2023 03:38:32 am
Most of the time I don’t make comments on websites, but I'd like to say that this article really forced me to do so. Really nice post!
2/19/2023 08:44:28 am
thank you for a great post.
3/7/2023 04:14:53 pm
I found your this post while searching for some related information on blog search...Its a good post..keep posting and update the information.
3/22/2023 09:08:08 am
Thank you again for all the knowledge you distribute,Good post. I was very interested in the article, it's quite inspiring I should admit. I like visiting you site since I always come across interesting articles like this one.Great Job, I greatly appreciate that.Do Keep sharing! Regards,
4/28/2023 01:01:00 am
I think that thanks for the valuabe information and insights you have so provided here.
4/29/2023 10:05:51 pm
Great survey, I'm sure you're getting a great response.
4/30/2023 05:41:54 am
Pretty good post. I just stumbled upon your blog and wanted to say that I have really enjoyed reading your blog posts. Any way I'll be subscribing to your feed and I hope you post again soon. Big thanks for the useful info.
4/30/2023 12:10:48 pm
This is my first time i visit here and I found so many interesting stuff in your blog especially it's discussion, thank you.
5/3/2023 02:38:44 am
Dashiki Store Verkauf weiße Dashiki-Shirts und schwarze Dashiki-Shirts, die für Dashiki für Männer und Dashiki-Frauen geeignet sind
5/8/2023 10:51:15 pm
thanks this is good blog.
5/18/2023 09:44:52 am
What a fantabulous post this has been. Never seen this kind of useful post. I am grateful to you and expect more number of posts like these. Thank you very much.
5/19/2023 10:57:14 am
Hey what a brilliant post I have come across and believe me I have been searching out for this similar kind of post for past a week and hardly came across this. Thank you very much and will look for more postings from you.
5/23/2023 12:34:00 pm
I am really surprised how great services they offer at very informative platform! Such an amazing setup for our problems! I would like to recommend them to everyone! They are perfect in their work!
5/25/2023 01:11:46 am
Thank you very much for the sharing! COOL..
5/27/2023 06:03:57 pm
I appreciated your work very thanks
5/28/2023 03:01:51 am
Thanks For sharing this Superb article.I use this Article to show my assignment in college.it is useful For me Great Work.
5/29/2023 05:56:52 am
I can see that you are an expert at your field! I am launching a website soon, and your information will be very useful for me.. Thanks for all your help and wishing you all the success in your business.
5/31/2023 04:18:07 am
Wow i can say that this is another great article as expected of this blog.Bookmarked this site..
6/1/2023 08:21:03 am
Your blog provided us with valuable information to work with. Each & every tips of your post are awesome. Thanks a lot for sharing. Keep blogging,
Leave a Reply.