jdp's blog

DYNAMIC EQUILIBRIUM (?) IN RIVERS

Nicholas Pinter, a Southern Illinois University geomorphologist, gave a nice talk yesterday on rivers and flooding in the 21st century as part of UK’s Water Week. Pinter’s talk got me to thinking about the concept of “equilibrium” in environmental systems and what it means to both geoscientists and laypersons. Pinter correctly noted that rivers tend toward dynamic equilibrium, and more specifically, dynamic metastable equilibrium. This means three things: First, the system (river) is more or less constantly changing (the dynamic part). Second, equilibrium is of the type envisioned in mathematics and systems theory—that is, a state or condition the system settles into after a change or perturbation, with no further connotation other than that the response to the change has run its course (I’ve called this “relaxation time equilibrium” in my work). Third, “metastable” means that these equilibrium states are not necessarily stable and self-maintaining, and may be sensitive to future disturbances—even relatively small ones. Pinter’s message is that dynamic equilibrium in rivers means that rivers are constantly changing.

THE TRIAD

Explaining and understanding Earth surface systems almost always requires some triangulation between three different sets of factors. The first, examples of which are shown on the lower left corner of the triangle below, are general principles and relationships that apply everywhere and always. Second, on the upper point, are environmental factors--characteristics of locations and regions such as climate, geology, etc. On the lower right of the triangle is the third set of factors, related to past events and time available for the system to develop.

This can be generalized as laws, place, and history, as shown below. 

BADASS GEOMORPHOLOGY

Yesterday I was honored to give the annual Linton Award lecture to the British Society for Geomorphology at the University of Manchester. Many thanks to the BSG for making my attendance possible, and to the U. Manchester geography department for putting on a good meeting. This is the abstract of my talk, entitled Badass Geomorphology:

RIVER RESTORATION & REHABILITATION

 

Yesterday I heard a very interesting river restoration workshop at the British Society for Geomorphology meeting. What I’m about to discuss was not the focus of the workshop, but it was triggered by thinking about geomorphology, hydrology, and river science in stream rehabilitation and restoration, which is a big business now.

The stream restoration problem is often portrayed as something like this:

 

That is, the stream is currently in some kind of degraded, suboptimal, unwanted state. The goal is to restore it to a “natural” or some more desired condition, often conceived as whatever the stream was like before the degradation commenced. There are a number of problems with this, one being that in many cases the pre-existing state is not known. Even if it is, since rivers—like other landforms and ecosystems—are dynamic and changeable, there is no particular scientific reason to believe that, in the absence of human-driven changes, the river would still be now as it was decades ago.

TUITION AND TEACHING

 

I am off to a meeting today, where I will meet with an old professional friend who teaches at an Ivy League university. Also today, the first bill arrived for my daughter’s tuition at a prestigious Midwestern private university. My colleague has lots of time for travel, as he teaches, over the course of a year, about half of what those of us in state universities teach. But what struck me today was not sour grapes about teaching loads (I actually think teaching is important, and usually enjoy it—it’s the administrative BS of the state university that drives me up the wall). It was wondering how much of the outrageous sum I’m about to shell out is actually funding my daughter’s education, vs. paying professors at that university not to teach very much.

One thing I can say about my university—and many other state universities—is that while we do not have as many big-name academic superstars as some of the prestigious private schools, we do have some. And if your kid comes here, she or he has a reasonable shot of actually encountering them in the classroom. I wonder to what extent that is true in the Ivies and their peer institutions. I hope, for the sake of my daughter and my own consumer self-esteem, that my cynicism is misplaced. 

CAROLINE, THE THERMODYNAMIC MIRACLE

"In each human coupling, a thousand million sperm vie for a single egg. Multiply those odds by countless generations, against the odds of your ancestors being alive, meeting, siring this precise son; that exact daughter...until your mother loves a man ...and of that union, of the thousand million children competing for fertilization, it was you, only you...(it's) like turning air to gold... a thermodynamic miracle."

Those words, from Alan Moore’s “Watchmen,” indicate that despite the common features of all members of our species, the biological laws and relationships that apply to us all, each of us is unique in some way. I am reminded on this on the occasion of the birth of my first grandchild, Caroline Harper Phillips, yesterday.

 

Caroline Harper Phillips, age <1 day

 

INFINITE SAND GATORS

 

This unusual bedform was created by the self-organizing dynamics of ocean waves, wind, sand, and shells a couple of days ago.

OK, it wasn’t. It is the work of a vacationer at Myrtle Beach. But it got me to thinking, not only about what an awesome sand sculpture it is, but about uniqueness and probabilities in Earth surface systems.

In theoretical physics, the “many worlds in one” (MWO) concept holds that, with unlimited space and time, any outcome not forbidden by the first and second laws of thermodynamics (laws of conservation of mass and energy) will eventually occur (Vilenkin, 2007 is the standard source for MWO; I encountered it via Koonin, 2012). Thus, on some beach, somewhere, some time, waves and wind have independently sculpted a sand alligator.

FLUVIAL BEACHES

 

A sandy beach is actually sometimes a pretty good place to think about fluvial forms and processes. The small streams, swashes, outfalls, and ebb-tide channels can be examined up-close, and they change several times each day, with the tidal cycle (here where I am at the moment in South Carolina, two high and two low tides each day). Thus Buck Swamp Creek, which discharges on the beach near where I’m staying, goes through four cycles of change a day.

A lot of work in recent years suggests that unless the material is pretty cohesive (which of course beach sand is not), without vegetation stream channels tend to be braided, and single-channel meandering forms are rare. You can see that here, where the marsh creeks—with plants and mud—are meandering, but develop nice braided patterns where they cross the sand. But along a mud coast near Cairns, Australia, where I spent some time last (N. hemisphere) summer, the same kinds of channels across the tide flats were meandering.

Braided channel crossing the beach at low tide, Myrtle Beach, SC. 

MYRTLE BEACH DAYS

 

A blessing (in my view) or a curse of being a geomorphologist is that you are never completely “off the clock,” because there are landforms and landscapes everywhere, and in all but the most heavily urbanized and industrialized areas, you can almost always see something interesting.

So here I am on vacation in Myrtle Beach, SC, a destination and timing selected because my son and daughter-in-law live here, and my grand-daughter is due within the next 10 days or so. I went out for a run on the beach this morning (one of the few surfaces my bad knees tolerate any more), and could not help but think that it would be a great day for a class field trip. Not a classic summer beach day by any stretch—cloudy, rainy, lightning out over the ocean, and a strong wind from the east, not typical at this time of year. But a lot to see along the shore.

TOPOPHILIA, TOBACCO, & TACTICAL WEAPONS

 

Topophilia is the affective bond between people and places, and also the title of an influential 1990 book by human geographer Yi Fu Tuan. I was thinking about this yesterday as my wife and I drove across the North Carolina coastal plain to visit relatives. Highway 70 from Raleigh east toward the coast is not a scenic drive by any objective standard. The topography is flat and monotonous, and the road corridor is infested with strip malls, billboards, convenience stores, and tourist traps.

Yet, as it does every year when I make the trek east from Kentucky, this crappy stretch of highway triggered fond associations with eastern North Carolina—topophilia, I reckon. I am a native of the region, taught for nine years at East Carolina University, and my wife’s family lives there. My post-dissertation field research sites were there, and there are some sites I still monitor during my family visits.

 

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