The Infiltration Game - Soils and Floods
Dr. Jesse Reimink: [00:00:00] Welcome to Planet the podcast where we talk about our amazing planet, how it works, and why it matters to you. I've got a little bit of a cold.
Chris Bolhuis: Yeah, I can hear
Dr. Jesse Reimink: You know, I went
Chris Bolhuis: When I was going to get my beer, I left my headphones on and I could hear you like clicking and scratching all the way out to my garage. I was kind of, you are really lucky you didn't say anything bad about me.
Dr. Jesse Reimink: One of the rare times when you walk out of the room and I [00:00:30] don't say something bad about you.
Chris Bolhuis: I know. Like you could have said, Oh, this guy is such a piece of work.
Why do I do this with him? And you could have been totally serious. And I'm listening, I'm a hundred feet
Dr. Jesse Reimink: Here's the thing. When recording's on, I know I have to be nice to you because our listeners are always defending you. they think I'm a little bit mean to you.
Chris Bolhuis: do we have wounded Jesse today? I like the, listen,
Dr. Jesse Reimink: not at all.
Chris Bolhuis: you need to suck it up. I quit being so soft.
Dr. Jesse Reimink: I have two questions for you, Chris. You ready? Okay. First of all, [00:01:00] do we have any updates from Joyce?
Chris Bolhuis: So. Not, let me think now. Not really. I did tell her that we talked about her in her last recording or one
Dr. Jesse Reimink: wait, she didn't know about it. She fell asleep in the episode we started talking about
Chris Bolhuis: I, no, it's one that we haven't released yet. And I told her, I said, all right, mom, we talk about you. And, um,
Dr. Jesse Reimink: what'd she say to
Chris Bolhuis: you need to be very defensive of your, of your favorite youngest son.
Dr. Jesse Reimink: That's pretty good. Well, [00:01:30] I'll, uh, I'll, I'll tell you one of my family members who shall go nameless. Sort of said, you know what? Chris's mom is getting a lot of airtime on your podcast. I think I should be getting some more airtime.
Chris Bolhuis: Oh, Linda, Linda, Linda is welcome. Tell Linda though, she has to start emailing
Dr. Jesse Reimink: That's true. Joyce only gets airtime by emailing me. Yeah, that's true. That's true.
Chris Bolhuis: right.
Dr. Jesse Reimink: question number two, Chris, which I just noticed, you know, we use Google Drive and Google Docs for, this is not an ad, we're not supported by Google, but,[00:02:00] we use Google Docs for our scripts and, uh, you know, usually we might have like a rough outline open next to us while we're doing this.
I just noticed your name is Chris Bolhuis, lowercase c, lowercase b. Do I come in as, Dr. Jesse Reimink, you know, with the little, like, name tag that shows up? Is there a doctor in front of it or not?
Chris Bolhuis: There is not, and I would do whatever I had to take and spend. Whatever amount of money I had to spend, climb whatever mountain I had to climb to make sure that was not the case.
how in the world does this happen? [00:02:30] Yours is capital, Jesse. Capital, Reimink. that's not okay. What'd you
Dr. Jesse Reimink: I think it's the way it should be. I think Google recognizes, that, you know, one of us needs to be capitalized and one of us doesn't.
Chris Bolhuis: if that's what you need. I can do that for you, Jesse. Okay. If that, if that helps you, if it helps you to tear me down, then go right ahead. If that makes you feel better about yourself, everybody else out there knows what we call people like that.
Dr. Jesse Reimink: Yeah, it's true. It's true.
Chris Bolhuis: it's okay.
Dr. Jesse Reimink: Well, I...
Chris Bolhuis: Okay. [00:03:00] So you're just easing back into your professional life. Like what's going on at the Penn State University? What are you, what are you doing? What are you doing there?
Dr. Jesse Reimink: The Penn State University, well, we're in the throes of football season here. Um,
Chris Bolhuis: Okay.
Dr. Jesse Reimink: the, the place just, they're, yeah, And, uh, the, the place changes a lot in football season. You know, there's a stat, Chris, I didn't. I didn't know this until I moved here, but the city of State College is like 40, 000 permanent residents, maybe something like that.
During the school year, it blossoms [00:03:30] to, I don't know, 90, 000 or 100, 000 people, with all the students that move to campus, obviously. But then, six weekends a year, the home football games, the town becomes the third biggest... in Pennsylvania, because a hundred thousand people come for the game and then like 200, 000 people come to tailgate to just be near the game.
So it becomes this huge place. I mean, it's the craziest thing, you know, in Michigan, we always had these like in the winter, some of the road signs [00:04:00] would, they'd had, you know, those like. aluminum flaps that would kind of fold down over some signs like they'd fold up a stop sign or a yield sign for the summer and then in the winter they'd fold it down so that it's like visible we have that here except it's all the street signs for football game weekend so like fold down and it'll be different directions if it's a football game weekend you'll only be able to go one way on this road and they'll fold down the one way road sign so like the entire traffic pattern in the whole area changes on football game weekend it's crazy
Chris Bolhuis: I had no idea. [00:04:30] does anybody in the geology department at Penn State do seismic analysis? Like, have you done any,
Dr. Jesse Reimink: yeah they're
Chris Bolhuis: know, analysis of when touchdowns are scored and things like that at Penn
Dr. Jesse Reimink: Yeah, they used to. I think, um, there's a research group that is doing this crazy stuff that I, I kind of struggled to understand, but they're using fiber optic cables to do seismic analysis. So you can like look at the travel times of light along the fiber optic cables, and you can get some seismic data from that.
so they do, they can detect like Football games and touchdowns and things like [00:05:00] that. And as we talked about in like literally our fourth episode, I think we talked about the seismic quieting of earth during COVID when there's no trucks on the road and stuff and no football games. And so we kind of, we, I think we touched on this going back now, what,
Chris Bolhuis: Yep. Right. Because University of Michigan has done this. They can determine when Michigan scores a touchdown based on the seismic waves and the noise. And yeah,
Dr. Jesse Reimink: I saw an article recently, I think it was out of one of the Washington schools, where they did this for a Taylor Swift concert and saw the start of all the [00:05:30] Swifties stomping on the ground.
Chris Bolhuis: okay. I have to ask you this because
Dr. Jesse Reimink: Can I identify Taylor Swift? Yes, I can.
Chris Bolhuis: I can too. She's not a limestone. Okay. I can always identify Taylor Swift. would you love to go to a Taylor Swift concert?
Dr. Jesse Reimink: Oh, wow, that's an interesting question. Hmm. Yeah, that's a good question. I would probably go with the right group of people. I wouldn't maybe love to go. Let's put it that way. What
Chris Bolhuis: Oh my gosh. I would go alone if I had to. [00:06:00] I would dance. Oh my gosh. I would. Yeah.
Dr. Jesse Reimink: That is not the answer I was expecting. I would go
Chris Bolhuis: are you serious?
Dr. Jesse Reimink: that's
Chris Bolhuis: I had to, I would rather go with Jenny. Jenny would be my favorite person in the world to go with, but, oh, I would go with anybody, because I would have so much fun.
Dr. Jesse Reimink: Okay, you and I and Tess and Jenny will go at some point to a Taylor Swift concert. That would be just hilarious.
Chris Bolhuis: Oh, [00:06:30] you, you would, I think, be enlightened
on my
Dr. Jesse Reimink: I would get to know a side of Christopher Bolhuis that I shockingly have never seen before. I've never seen concert going Chris.
Chris Bolhuis: You have not. I love, love live music. You know, I've been to Red Rocks many times and I'd love live music and I am, I become a dancing, singing machine.
hmm. It's true.
Dr. Jesse Reimink: Okay. Well, we know how to bribe Chris Bolhuis now.
Chris Bolhuis: How did we get on Taylor Swift? that come from?
Dr. Jesse Reimink: seismic, uh, seismic analysis.
Chris Bolhuis: Oh, yeah. Okay. That's right. [00:07:00] Yeah in Washington or something.
Yeah. Okay. All right, Jesse. Shall we get down to business now? Are we good to
Dr. Jesse Reimink: So today, Chris, we have another, we've had a great series of listener questions. I mean, not that we don't have good listener questions all the time. We just have had several that, okay. If you're listening to this and you've sent us a question, we haven't addressed it, it's because it's not like in our frontal lobe, we kind of get stuck in schools of thought.
I think we've been talking a lot about streams recently. So anything related to streams is kind of like.[00:07:30] in our frontal lobe
Chris Bolhuis: No, I'm sorry. I just want to interrupt you. And the other thing too, Jesse, is that we're getting now a lot of emails. and so it's More difficult for us to do this and, you know, respond to everybody and that kind of thing. I mean, we've had a lot of growth and it's, it's, it's a good problem to have, but we have to be selective just from volume.
Dr. Jesse Reimink: so that was a great humblebrag, Chris, by the way, but also, if you're, if we haven't replied to you in a little while, you know, don't [00:08:00] take offense to it, we'll get to it, you know, things got to click into place, like we're thinking about streams a lot, so this email from Robert stood out really well, it's like, oh yeah, totally, that's an episode, that's, that's something that would totally fit in with what we're thinking about right now, and sort of related, the question from Robert related to, um, devastating flood in Libya.
And the question he asked was why does rain run off so quickly in arid environments and also on alluvial fan deposits other than their steepness? So the question is like, why arid regions do we get more flash floods? I think if we could kind [00:08:30] of distill that down, right, Chris, is that, was that a fair assessment of sort of a distillation of the question?
Chris Bolhuis: I think so because a lot of people think arid, the ground is super, super dry, that rain is going to soak into that very, very easily and very quickly. And so this wouldn't be a problem, but that's not what happens. And that's what we're going to talk about as we dive into this thing that is called infiltration capacity a little bit later on.
Before we get into that though, let's set up at what happened. this has been [00:09:00] all over the news, but let's just set this up so that everybody's on the same page. So, there was a recent Mediterranean storm that hit the northeast coast of Libya. Two dams failed above the port city of Derna.
I mean, They're not done yet with the death toll of this thing. It's horrific. a human tragedy that is hard to like put a thumb on. The storm that did this. dropped 414 millimeters, which is about 16 inches of rain in a [00:09:30] day. Now let's frame that with what's typical.
Usually, this area sees 1. 5 millimeters, about a tenth of an inch of rain during the entire month of September. So this is...
Dr. Jesse Reimink: an amazing.
Chris Bolhuis: event that
Dr. Jesse Reimink: Amazing amount of rain. I mean, just an incredible amount of rain.
Chris Bolhuis: So that's what happened and the results are just catastrophic beyond measure. let's talk about Jesse. What [00:10:00] are the things that contributed to making this so horrible?
Dr. Jesse Reimink: so I think Chris that we have to frame this, Derna is built on an alluvial fan. So let me define what an alluvial fan is really quickly. And I think people have probably seen this. So it's kind of easy to visualize in your head.
Imagine you're flying a plane. Over the desert and there's mountains to your left or to your right. I just watched the movie Dune a while back again. there's a lot of images of this, of alluvial fans. And so if you have big Rocky [00:10:30] mountains and you're in this desert landscape and you're flying over this Valley, there will be a big gully, a big Valley in the mountains and where that dumps out onto the plane, there will be this kind of.
Conical shaped hill of sediment, and that is the alluvial fan, it's basically a river flowing through the mountains, flowing steeply downhill, is carrying boulders, it's carrying sand, it's carrying silt, stuff of all sizes, it flows out, hits that valley floor, and it slows down really quickly, [00:11:00] In really dry places, it evaporates really quickly, and it just dumps all of the sediment into this really steep sided, what's called alluvial fan.
It's usually kind of like a half cone shape, or a quarter cone shape, where the top of the cone is pointing up in the valley.
Chris Bolhuis: Yeah. I think of them kind of like those, Chinese fans, you know, that you make with folded paper and you, you fan them out, you know? And so well, they look like this, right? And the tip of that fan points upstream. It points up into the valley where the mountains are.
that's how I kind of [00:11:30] explain it and frame it.
Dr. Jesse Reimink: And they're very common in mountainous regions, especially arid mountainous regions. So ones that get a limited amount of rainfall don't have necessarily a ton of vegetation around kind of a desert environment. Southwest U S in the basin and range environment has loads of alluvial fans.
Any mountain valley that comes and dumps out onto the main valley floor will have an alluvial fan attached to it.
Chris Bolhuis: Basically, if you have a, River coming out of the mountains. It's confined by a valley. It's steep sloped and erosion is the dominant process It is moving [00:12:00] stuff and then during these events these flood events It's moving massive amounts of material and massive size material, you know in geology We call that the competence and the capacity they go up Exponentially actually and then it comes down and hits that broad valley floor and it rapidly slows down.
So it changes from an erosive thing to a depositional environment very quickly. And that's what results in this kind of like fan shaped deposit. And then I think they're really cool looking actually. And then. If you have a lot of these in [00:12:30] one area and they kind of coalesce together, you know, or the, edges of the fans merge together, then that in geology, we call that a pahata.
Dr. Jesse Reimink: And so, uh, you know, the visual of this, and you can look on, on Google and, and just look up durna images and, you know, it's kind of cool to see this because the city is built right on alluvial fan. It dumps out into the ocean in this case.
So it's a mountain valley, a big, river system, mountain valley coming out of the mountains, hitting the ocean. Um, dumping an alluvial fan right there. So we've got this relatively steep alluvial fan. The sediment deposition there is [00:13:00] relatively steep sided, sediment.
So that's the, the geological setting. And then
Chris Bolhuis: Well, there's one thing that I want to add to that, and that is that it's also in an arid climate. And what you get with this then you don't typically get drizzly rain. Instead, you get cloudburst kind of events, these cloudburst type storms that result in rapid amounts of water hitting the ground that runs off like surface runoff instead of [00:13:30] seeping into the ground, which we call infiltration.
And that's where we're going to go here
Dr. Jesse Reimink: And, you know, there's a lot to be discussed, I think, in the, especially in this sort of climate change, area around the intensity of rainfall events and the intensity of weather events that we're experiencing globally, as, uh, climate change as a potential driver for an increase in the intensity of these things.
We're not going to really touch on that here. we're just going to leave it as, Suffice to say, this was a ton of rainfall in a very short amount of time. So we got this intense, intense rain event, basically. So,[00:14:00] that's the kind of recipe we're dealing with here.
And so with that, Chris, I think we need to touch on this term. You, you briefly mentioned, which is infiltration capacity. And this is really, it's the ability of soil. To soak up water and how much water and how quickly it can soak it up. So it's kind of both the rate and amount of water that soil can soak up internally.
think of the water going into the soil versus running on the surface of the soil. [00:14:30] So we get surface runoff, which is running along the surface, and then we get infiltration, which is water percolating down into the soil, whatever's at the surface percolating down into that.
Chris Bolhuis: Jesse, do you talk about this with your intro classes, infiltration capacity? In other words, like, I mean, the term kind of makes sense. To infiltrate means to penetrate into, and the capacity is. It's ability to allow this to
Dr. Jesse Reimink: Exactly. So there's two important things there. so to answer your question, we, we kind of talk about it. I mean, it's, it's not a [00:15:00] long discussion, but a little bit, and there's a lab that it talks about stream runoff and things like that. So It is kind of part of that discussion, but there's two important points to capacity.
First is the amount of water it can handle. So how much volume can you put in there and how quickly can it absorb it? because if you're getting 16 inches of rain in 24 hours, you not only have to put a lot of water in the soil, you have to. got to be able to push it in there really quickly.
It's not like you can just let it sit there and soak up over days and days. It's got to go in really, really quickly.
Chris Bolhuis: [00:15:30] Alright, I have a question for you. Maybe two questions. One is, I would like to see that lab that you do.
Dr. Jesse Reimink: Okay.
Chris Bolhuis: Okay, so you need to send that to me. The other thing is, I feel like you need to emphasize this more. I think this is a really important issue and topic actually, and it's something that I want to emphasize, especially as we get into the factors that affect infiltration capacity, because there is an anthropogenic issue that is created here with infiltration capacity.
That's a [00:16:00] human induced, direct, and big time effect. on runoff and then what happens to the rivers as a result. So I feel like you need to have a discussion with your Penn State colleagues and you need to move this up to, this needs to be a more important topic.
Dr. Jesse Reimink: I agree. I agree. Um, it's, it's one of those ones where when you look around, our area, the difference or the variability and infiltration capacity is not much. There's a lot of soil around here that has basically very similar [00:16:30] infiltration capacity. And so our stream exercise, is relatively basic.
It's measuring the stream. It's looking at a stream cross section. We have a lot of meandering streams. So our meandering stream discussions are much more relevant to this area because a lot of the stream issues we run into around here in Pennsylvania are ones where humanity society has, has sort of, You know, confined to meander in a certain way and it's changing the downstream effects.
So that's like a more impactful, process to talk about for this specific region. But anyways, I agree with you [00:17:00] completely. Infiltration capacity is a super important thing because we'll end with this because this is one principle or one process. We can change a lot as humanity.
Chris Bolhuis: That's right. So we're going to move that part of our discussion to the very end then, Jesse. And then at the end, I want to come back to it and say, do you still think that Penn State should not be moving this to the forefront of your discussion? Cause I'm not done with this. I think like it's, I think it's a big deal.
I'm passionate about it, obviously. and when I'm passionate about it, Jesse, it means I'm
Dr. Jesse Reimink: Well, [00:17:30] I mean, it doesn't everything mean you're right, Chris. Um, so I think we can, Chris, move into, we've set the stage really well here with where Derna is, and, and the sort of event we're talking about.
Let's talk about the key features or the key factors that influence the ability of the soil to soak up water, which is this infiltration capacity term. The first one we've already Okay. Touched on, I think, it's the intensity and duration of rain. So how much water are you getting and how quickly are you getting that?
Because ultimately [00:18:00] your soil has to. Soak that thing up. So, so that's one thing that, that could impact it, right?
Chris Bolhuis: because if you have this cloudburst thing that dumps a lot of rain in a very short period of time. that's going to favor a low infiltration capacity as opposed to something like a drizzly event that lasts a longer time given it then more time to soak in before it runs off the
Dr. Jesse Reimink: and so this is really, a massive factor if you want to know, am I going to flood, experience a flash flood or not, is [00:18:30] you have to compare your soil level. Infiltration capacity, which is kind of a fixed number versus the amount of rain you're getting in that event. And if the volume and speed rate of rain is greater than your infiltration capacity, you're going to flood.
it's kind of a law there that if it's greater than your infiltration capacity, it's going to flood. If it's not, your soil can then soak up the amount of rain you're getting in that event, right? And, and you're not at risk of flooding. So it's a really important thing for predicting, flood events and something people consider when you're looking at.
a drainage basin and seeing a [00:19:00] weather event and trying to figure out, is this a flooding event? We need to worry about or not.
Chris Bolhuis: So let's move into the second variable, which is. I think intuitive, it's the slope of the land. Slope of the land is how steep the topography is. And we've already laid this out, that Derna is on an alluvial fan, and they tend to be steeper sloped. Well, the steeper the slope, the lower the infiltration capacity, because water needs time.
It needs time to soak into the ground, into the soil, into the [00:19:30] regolith, and with a steep slope it doesn't have time. So that favors surface runoff, and surface runoff is the exact opposite of infiltration capacity.
Dr. Jesse Reimink: Service runoff is potential flood. Right.
Chris Bolhuis: that's right. So I think those two, Jesse, are the most intuitive intensity and duration slope.
But now we get into some of these other things that maybe aren't as intuitive, that can really dramatically affect infiltration capacity.
Dr. Jesse Reimink: And I hate to admit [00:20:00] this one, Chris, number three, I really, it kind of pains me to admit this, but biology matters here uh,
Chris Bolhuis: You said it,
Dr. Jesse Reimink: I know. You made me say it this time, but it does. This is like we talked about with stream meanders and vegetated regions and non vegetated regions. It changes the physics of stream meanders.
biology changes the physics of soil infiltration capacity. And there's a couple different ways in which it does that, Chris. So, so this is like vegetation matters [00:20:30] or biology matters is the heading here for number three. And there's a couple of subheadings, right? hey, it's
Chris Bolhuis: so Jesse, let me interrupt you a second. You're the one that said this. and I take issue with this.
You said, this gets to the heart of Robert's question, dealing with the biology, the vegetation, the vegetative cover, and what it does. So, you really think that this is the most important factor affecting what happened in Derna? So I'm going to let you run a little bit, okay, with this and explain [00:21:00] why you're so passionate about the vegetative cover and what it did to make this such a horrible event.
That's
Dr. Jesse Reimink: well, I think it's more what it didn't do. And so in Derna, it's an arid region. and the reason I think this is part of Robert's question is because Robert, very, uh, intuitively. said why does rain run off so quickly in arid regions, other than steepness, So if we rule out steepness as, uh, a factor, then this one is, to my mind, the, most important. Soil, without... Vegetation on it is more densely [00:21:30] compacted. vegetation does a lot of stuff that breaks apart the soil. There's plant roots that are going down in it, there's dead organic matter, in with the soil.
We have this soil horizon that's a lot of organic matter in there, and organic matter is not very dense, means it has a lot of porosity and permeability to soak up more water. So there's a couple factors, a couple reasons why plant matter, organic matter, breaks up soil. takes the same amount of sediment and makes it more voluminous and therefore more ability to [00:22:00] soak up water.
Chris Bolhuis: And another thing that vegetation does is it simply slows surface runoff down. think about it, if you have, Water flowing over the surface, but it's flowing through grass. Let's say the water has to go around and, you know, it's a very intricate path that it has to take and slowing it down.
And that's what the soil needs. It needs time to absorb it. So it also
Dr. Jesse Reimink: Yeah, and you know, related to that, Chris, which is, I think, very intuitive to what most people imagine. A steep [00:22:30] slope with sand, if you pour water across that, it's going to draw the sand down. if you put trees or grass over that and you pour water on it, it's not going to, erode as quickly.
And not eroding... means that the water has to infiltrate into the soil more, and so I think that's kind of an intuitive one, like just imagine a hillside that has trees on it, and one that's barren, that just has rocks and soil on it, and if it's a big rain event, with the trees, it's, it's gonna hold the soil in place more.
So, it does a couple of things.
Chris Bolhuis: something just popped into my [00:23:00] head. Can I, can I do a little side tangent? Just a second, just real quick. alright, we have this problem in the Mississippi Valley, here in the United States, where agriculture is exposing fresh soil and fresh regolith, like in the fall and so on, when they go and cut this off, right?
if you combine this now freshly exposed soil with a cloud burst kind of event, heavy, big, intense rain droplets, right, they impact the ground and they're dislodging sediment, which helps also you get [00:23:30] runoff and a lot of erosion then because of that. And so. They're trying to get creative in the Mississippi Valley to deal with this.
Like as they cut their stuff off, they're just kind of more mulching it up dropping it back onto the soil to act as kind of a, protective covering to minimize this impact
Dr. Jesse Reimink: Oh, interesting. Wow. You know, okay. Another random side tangent here. I just had a discussion with a colleague that I think you'd find very interesting. So this colleague went in took a forestry class [00:24:00] for, for reasons, but took like a, uh, a weekend, long weekend, like forestry clinic up in the Northeast.
Chris Bolhuis: reasons,
Dr. Jesse Reimink: I mean, for fun, right? Who doesn't, who doesn't, you know, go and take a forestry, long weekend. This was up in the Northeast. So like Maine, Vermont, New Hampshire, you know, upstate New York, that kind of area, picture that the sort of white mountains, uh, the Catskills. and one of the things they were talking about was the.
Amount of beaver dams that used to be there sort of pre industrialization pre European beaver trapping [00:24:30] and the number was massive I'm making this number up, but it was something shockingly big, like 27 beaver dams per square mile or something, something crazy, like crazy high amount.
You know, I, when I envision upstate New York, Catskills, Chris, you and I drove, have driven through there many times collecting rocks, like that area, right? You've got these beautiful forested mountainsides, with this beautiful clear stream, sort of pebbly bottom, rolling, through it, you know, fly fisher guy, hanging out there in the river, like, That's the visual.
the [00:25:00] conclusion was that stream never would have existed pre European beaver trapping. Cause that would have just been a beaver dammed river. so the conclusion is, get rid of all the beavers and actually the entire landscape erodes faster because there's not all these small little dams damming up the entire river system.
so these clear running streams, Never used to be there. that's a dramatic change to the entire landscape that all these rivers are running straight and faster and eroding quicker and carrying a bunch more sediment out to the ocean.[00:25:30]
anyway,
Chris Bolhuis: that is a very interesting conversation and I would put that in the category of a thought
Dr. Jesse Reimink: absolutely a thought experiment. Yeah, like, because the, the, you know, this is where our conversation kind of went. It was like, well, wait, the average erosion rate that we measure today. Which people go out and measure this in Pennsylvania. Like it's a really important parameter when we're thinking about how has the earth evolved over long timespans?
Like, what is the erosion rate? Those all might be wrong. they might not apply more than 200 years ago. we take that number we measure today and back [00:26:00] calculate 10, 000 years, we could be way off with that because we're using a number that is post beaver, post beaver life in the Northeast anyway.
Yeah.
Chris Bolhuis: That is, that is all right. Hey, good side
Dr. Jesse Reimink: Hey. Okay. Back, back at it here. so biology matters for, for this, this stuff for in soil infiltration rate, for a variety of reasons, it anchors the sediment, it breaks up the sediment, and actually dead organic matter in the soil itself adds a lot of porosity.
Chris Bolhuis: And, Derna, arid [00:26:30] climate, fan, probably not a lot of vegetation.
Dr. Jesse Reimink: a lot of vegetation. Exactly. Exactly.
Chris Bolhuis: So, low vegetation equals high runoff, low infiltration capacity. Bottom line, okay? Alright, let's segue into the fourth variable that we're going to talk about, which is soil texture, and there is some overlap with here, so let's kind of move fast through this, but this is a broad kind of sweeping term, but with soil texture, we're referring to things like porosity.
[00:27:00] Generally speaking, soil that has a higher porosity means it has a higher percentage of air spaces between the grains. it's got a lot of space between the grains. Think of like pumice. Maybe that's a bad example, but pumice has a really high porosity. It wouldn't be very permeable and it wouldn't allow water to soak in because the, pores aren't connected with each other.
But in soil, they often are. And so high porosity, high permeability, high
Dr. Jesse Reimink: I really don't like the fact you brought up pumice for reasons we've discussed previously on [00:27:30] this podcast, but how about a bucket of sand? That's the analogy you use in class, right? As a bucket of sand, a bucket of sand can hold a lot of water. If you pour water into that five gallon bucket full of sand, you know, you're going to pour a bunch of water into that, right?
So there's a lot of extra
Chris Bolhuis: You know how much water?
Dr. Jesse Reimink: How much?
Chris Bolhuis: You can pour about two and a half gallons of water in a five gallon bucket of sand, which means the porosity is
Dr. Jesse Reimink: 50%? Very good. We often use fractions for porosity. So 5 is the porosity of sand, right? And,[00:28:00] have different porosities, right? another factor that affects soil texture is the sorting. How well... Sorted is the soil and usually the better sorted the higher the infiltration.
this can vary across different sediments. So sand is a great one, really well sorted, loads of porosity. Water can just pour through. Sandstone or sand, sediment clay is a harder one. There's actually a lot of porosity in clay, but the pores are so [00:28:30] small that it doesn't percolate through very fast.
The permeability is not high. So you can't like push water through clay very readily, even though it can absorb a lot. So it kind of depends, but basically the more well sorted and the larger the grain size, the more, um, capacity of the soil has.
Chris Bolhuis: That's right. Let me provide an analogy of sorting, if you will. If you take a mason jar and you fill it with a bunch of marbles, a bunch of like, uh, smaller BBs, and a bunch of sand, and you mix it all up and you dump it into this [00:29:00] mason jar, that has a lower porosity because it's not well sorted. The grain sizes, These things vary immensely from sand all the way up to marble size.
And what happens then is those smaller particles sit in what would be the porosity, the pore space. And so that diminishes the porosity, which diminishes then the ability of water to seep through that stuff. okay.
Dr. Jesse Reimink: a good analogy.
Chris Bolhuis: and then the last part of the soil texture that we're going to talk about is this soil compaction, and that I think it [00:29:30] makes a lot of sense.
It's intuitive. The more it's compacted, the lower the porosity, the lower the permeability, and the lower the infiltration capacity is. But all of those fit into texture of the
Dr. Jesse Reimink: Yeah. And these can get really nuanced, like, you know, very, specific to a very specific region. So one hillside can have multiple, soil textures along it that are due to the different textures that are in that hillside.
So you can get highly variable soil textures, all right, Chris, the last one. Thank you. [00:30:00] which is the most counterintuitive, is prior wetted condition. And what we're saying here is wetted, W E T T E D. So, basically, is the soil dry, a little bit wet, or very wet? And this is a counterintuitive one, how do you break this down in class when you're talking about this?
Chris Bolhuis: let me give this a shot. so if the soil is saturated, then you don't get any infiltration. So prior wetted condition, we're just saying is the soil moist already not saturated [00:30:30] because then you don't get any soaking in it. If it's saturated, it's holding all that it can. But if it's just moist, the infiltration capacity goes way up and that's the part that's counter intuitive.
Dr. Jesse Reimink: compared, let me interrupt Chris, compared to a dry soil. So kind of this Goldilocks thing, right? You don't want to have no water in your soil. that's going to lower your infiltration capacity. You don't want to have a lot of water because you just can't fit any more than in your soil.
You want to have a little bit it's this kind of Goldilocks [00:31:00] thing.
Chris Bolhuis: I show a video to my students it's showing a moist lawn, then it shows a dried lawn, and then it shows Nolan that is very arid and just kind of like hard baked, right? And it's just simply take a cup full of water, flip it over, and you can watch the water drain into the wet soil just goes in like, like it's gone in the dry.
Grass, it, you flip the cup out and it seeps into it, but much, much slower. [00:31:30] And then if you take no grass and it's just really, really dry, the water just sits there, it won't soak in hardly at all. It takes a very long time for it to soak in. And that's what you get in an area like Derna. Libya is very, very dry, which favors runoff.
And we don't need to get into the weeds too far on this, but I think we can do something with this. Why is the prior wetted condition? If the soil is already just moist, it's damp. why does it increase the infiltration capacity? [00:32:00] Again, Jesse, I hate to do this. We go back to biology.
Dr. Jesse Reimink: I knew you were going to go this way. So can I, can I tell you, I'm going to tell you a story. So I had my dad my dad was a high school biology teacher and, uh, I had him in class and I remember this lecture from him. It's one of the only lectures I remember from my dad in biology class.
And he was talking about,
Chris Bolhuis: You know, you just hurt your dad's heart a little bit
Dr. Jesse Reimink: well, he knows my, uh, my longterm memory is just terrible, but this is, was describing capillary action, which is, I think where you're going with [00:32:30] this, right? And. the picture, the visual I have is he would, would take like a, I think it was, I might be getting this wrong, but so dad, you can let me know if, if you listen to this and I'm getting this wrong.
But basically I think he, I think he did it on the door, like on the wooden door of the classroom and he'd put like one drop of water on the door and it would beat up and it would kind of slowly like roll its way down. And then he'd take his finger and wipe uh, like a finger streak of water down it and put a drop of water at the top of that and the bead of water would [00:33:00] disappear immediately and a bead of water would appear at the bottom of the finger streak he put it was something along those lines where water beads up when there's no more water around.
but if there's water already there, it readily soaks up into the preexisting water. Is that where you're going with this or not? I just have this visual in my head.
Chris Bolhuis: I am, and that's a really good visual actually. well done, Ron. Um, so. I said we need to go to biology to do this because in biology You talk about the polarity [00:33:30] of water quite a bit so just a little bit of chemistry just indulge me a little bit here and you can cut me off if I get long winded but
Dr. Jesse Reimink: the chemistry. Come on, man.
Chris Bolhuis: yeah, so water is what they call a polar molecule, which means the molecule itself has an even distribution of electrons and protons.
But the thing is the structure of the water molecule, they are not evenly distributed. In other words, it's lopsided where the protons are on one side of the molecule and the electrons are on [00:34:00] another side of the molecule. So even though the overall molecule is neutral, no net charge, the molecule behaves like it does have a charge.
And so if you take Individual water
Dr. Jesse Reimink: Chris, let me just interrupt there real quick. Cause you know, the visual here is we've got H2O and the H's are both on one side of the O. And so you kind of have like a little bar magnet. You've got a positive end and a negative end roughly, Or a positive side and a negative side. That's kind of what you're describing here.
Chris Bolhuis: that's right. And so water [00:34:30] then behaves like it carries this electric charge. Well, the electrical nature of matter is that opposites attract. So water molecules can orient themselves where the positive end of a molecule is attracted to the negative end of another water molecule, a nearby water molecule where it feels that electrical pull.
And that's what causes water to beat up on like a freshly waxed car. Is this polarity uneven lopsided distribution of electrical charge, [00:35:00] which allows water to orient and then feel the pull of that, that attraction and beat up like that, that's what's happening, right? So if you have soil that's wet in the pore space below the surface, it's going to attract because of its polarity.
It's going to attract water above it on the surface and draw it down into
Dr. Jesse Reimink: That's exactly right. And the, and the, the reason that the biologists talk about this is this is how plants get water from the roots up to their leaves, right? This is how a big tall [00:35:30] tree pulls water all the way up from the roots is this capillary action, little capillaries in there.
and this is why plants, If they die, they can, you can get them too dry that you can't recover them is because the capillaries all dried out and they can't get water up there, but if they have a continuous stream of water, they can pull water up. and pull nutrients up with that all the way up to the, the top of the tree.
So that's why, biologists talk about this capillary action. That's exactly what's going on in soil, except it's drawing it down. Okay. So this capillary action is drawing water down into [00:36:00] the soil. if there's prior wetting, if the soil is completely dry, it beads up on the surface, which makes it spends more time on the surface is more likely to run off as opposed to infiltrate.
So, Another point here.
Chris Bolhuis: Another nod to biology. There we go. Or
Dr. Jesse Reimink: it. We're.
Chris Bolhuis: chemistry. Let's say that. Let's forget about that. Strike that out. It's a nod to chemistry.
Dr. Jesse Reimink: not about biology. Actually, it's
Chris Bolhuis: No! It actually is about chemistry, but biologists use it a lot because it explains [00:36:30] actually a lot of things. Okay, the polarity of the water molecule. Yeah. Um, one thing, Jesse, real quick, I do.
I'll take a blow up a balloon. And I'll take, like some fur and I'll create some static electricity on that balloon. so I'll charge it, right? And then I turn on a very small trickle, but constant trickle of water out of my faucet. And I'll put the balloon then that I just gave a charge to and I'll put it near the trickle and it'll bend the water dramatically.
Dr. Jesse Reimink: yeah. Yeah. That's a
Chris Bolhuis: It's, [00:37:00] attracted to that charged balloon surface. And so you can like bring it all the way around that trickle of water. And so all the students can just see it like bend really dramatically.
Dr. Jesse Reimink: Yeah. Yeah. Yeah. That's a good visual.
Chris Bolhuis: and again, it's just polarity, right? But that, that's a big time thing with, what happens in arid climates with this kind of like hard baked soil that has no moisture in it.
So it's not going to pull it down.
Dr. Jesse Reimink: so I, I think Chris, that, that leads nicely into, a non natural or an anthropogenic [00:37:30] effect that we're having. And this kind of comes back full circle to our discussion about the importance of stream infiltration for society. The end. And something we really have to worry about is, the most important thing, or one of the major important things that's at play here is that we like to build surfaces that have very low capacity for infiltration, anything made of concrete, anything made of asphalt roads, parking, locks, sidewalks, roofs.
I mean, all of this stuff, it's like rock. It's like pure rock. [00:38:00] Basically it has a infiltration capacity of, of next to nothing. And so basically all the water that hits that will run off it instead of infiltrate into the soil beneath it, even if the soil beneath it.
Chris Bolhuis: That's right, that's why I said that this is a really important thing, because if you do, let's say, a Google Earth image of a city, or anything really, that has human structures on it, you can easily do then a [00:38:30] grid search of, you know, what's the percentage of impervious surfaces because humans built that?
Like, and like you said, roofs and parking lots and storm sewers and all this stuff, right? And none of that is soaking into the ground. All of it's going into the ocean. it's running off the surface, and then it's getting to rivers really, really fast. And that's the opposite of what we want. Again, water needs time.
We're not given it time. And so, this is one of the reasons why we're seeing [00:39:00] dramatic rises in, let's say, 500 year flood events. We're contributing to that because if you take, like you said, with the whole beaver thing, right? Take the beavers away. And what does it look like? Well, take the humans away. And what was the path of water to get to a river
Dr. Jesse Reimink: exactly.
Chris Bolhuis: to what it is now?
I actually, a number of years ago, I had some students do three, three students did an independent study and they did a, one square mile area that encompassed our school, our high school.
And they did the [00:39:30] math on it, calculated all of the impervious surfaces from roofs and parking lots, driveways, roads, everything that they could count.
Right. And then they compared it to what it would be like if there were no human structures there. And then they, It compared the rate of flow to the rivers, how fast the water was getting there because of us. And we used green dye, dumping it onto parking lots at the same time that a cloud burst happened, you know, and watching that green dye to [00:40:00] show up in the river, it's dramatic.
I mean, it was getting there a minimum of a thousand times faster than it
Dr. Jesse Reimink: Yeah. Yeah. Yeah. it's a really important thing and there are solutions out there, you know, there's more, permeable concrete types. There are ways to, sort of build in natural, links to the groundwater system. so basically making little pockets of your parking lot that water can percolate through and get into the soil beneath it, and then kind of recharge the groundwater that way.
So there's ways [00:40:30] around this that, that are engineering, creative engineering ways around it.
Chris Bolhuis: that is a very, very cool engineering practice that's going on with these permeable asphalt and concrete around parking lots and things like this, you can do driveways with it. Think about that a second. You You would have no puddles on your driveway at all.
It just soaks right in and it soaks through really fast. Very cool technology. Okay. Jesse, we have one thing yet to cover with human impact on flooding.
Dr. Jesse Reimink: Yeah, exactly. Really flooding. This [00:41:00] is a bit of a separate thing from soil infiltration rate or soil infiltration capacity, but impacted this event in Libya. It's dams. We have a tendency, as humans, to watch for the biggest flood event, and then build a dam to hold in the biggest flood event.
And we are now in a point where we're experiencing a lot of very large flood events that are bigger than what we engineered for. is that safe to say, Chris, that, that we
Chris Bolhuis: Yeah, [00:41:30] it's, it's in part because of what we just got done talking about, but absolutely, plus you throw in climate change and we're getting. Bigger, more frequent events like this. So absolutely. But I have another thought too, Jesse, is that I feel like we're way more likely to build and construct an expensive dam in the first place.
Then we are likely to maintain that structure in. Perpetuity. Mm
Dr. Jesse Reimink: Yeah. No, that, uh, I, I agree completely. I think there's a lot more, [00:42:00] um, there's a lot more money to build new stuff than there is to fix old stuff in many, uh, in many aspects of life, I think. this happened, uh, in, in the flood that happened in Durma was a couple of upstream dams broke, because the flood event was just so large.
it overflowed the dam, broke the dam, went downstream, broke the next one. And, uh, And, and there you go. it, it makes a, catastrophe, a massive catastrophe when that happens.
Chris Bolhuis: So anyway, circle back to the top, Jesse. I think Penn State needs to [00:42:30] move this cold topic. Ha, ha, ha, ha. No, I don't forget things like this. I, I, I, I like an elephant. Okay. Um, that's good. I like that. I just think it's really important, and I think it's something that is so relevant is the anthropogenic side to this whole thing.
think it can't be neglected.
Dr. Jesse Reimink: I agree. I agree. I spend three days on talking about, you know, geochronology and about 15 minutes talking about stream combat. No, I'm kidding.
Chris Bolhuis: you're a typical professor, [00:43:00] aren't you? Oh my gosh, you guys. You did...
Dr. Jesse Reimink: there and listen to what I want to talk about.
Chris Bolhuis: That's right. You know what though, there's a part of that that I think is so good. The individuality that a professor can, bring to the, to the classroom is pretty awesome.
Dr. Jesse Reimink: there is some benefit to that. Although we do, this is the, the class I teach the, the intro to, geology class. Um, there's three sections. And so we have to maintain, I think it's like 80 percent similarity and we usually get pretty close to maintaining that. So because it's like got the [00:43:30] same, you know, course number, we have to, be broadly similar across the sections.
So
Chris Bolhuis: So here I have a solution to that too. You just have Penn State hire me. I'll teach all your intro
Dr. Jesse Reimink: there we go. Hey man,
Chris Bolhuis: one that teaches it and I can do exactly what I want then.
Dr. Jesse Reimink: listen, man, I've been preaching this for a long time around here that we just, you know what, let's just go hire this guy.
Chris Bolhuis: Yeah.
Dr. Jesse Reimink: It'd be amazing. How fun would that, how good would that be? And you know what? Our students would probably get a lot more out of it. So. Anyway,[00:44:00]
Chris Bolhuis: Another shameless plug by Chris Bolhuis.
Dr. Jesse Reimink: with, yeah, that's right, that's right, Humblebrag, um, with that, I think Chris, that's a wrap.
I mean, great, great question, Robert. It provided, I think, A really, uh, I think interesting and very important discussion about kind of the upstream side. We're moving upstream from, uh, streams. We've been on this stream thing and, and now we're talking about, kind of what happens before we get to a stream.
Uh, that's kind of interesting take on it. So hey, with that, keep sending us emails. We love that. Planetgeocast at gmail. com. [00:44:30] You can go to our website, planetgeocast. com. There you can subscribe. You can follow all of our old episodes and you can support us. We really appreciate that if you go there and support us.
You can also head over to our brand spankin new mobile app. Go to Camp Geo, type Camp Geo in your app store on your phone, on your phone or iPad or whatever you have. or just click on the link in the show notes there. We have a link directly to our new mobile app.
Chris Bolhuis: That's right. Have a good week. Cheers.
Dr. Jesse Reimink: Peace.[00:45:00]
