03 D Reading Riverscapes: Structural Forcing

It's Joe Eaton from
Utah State University.

And I'm going to talk to
you specifically about,

how to read river scapes
for structural forcing

in the photo shown here.

This is a beaver dam complex,
up on Spawn Creek.

It's actually where I take
you on a virtual field trip.

And, what we can see is, that what
would otherwise be a single thread

little mountain stream, is structurally
forced by this beaver dam activity.

They're bringing wood.

They're building dams.

They're backing up water.

They're spreading water out, etc..

This is what we're going to,
learn how to read a little better.

So, we want to build
your intuition about the,

the key processes of water
accumulation and beaver dam activity.

But, you know, broken into the component
pieces we spoke about in module one.

So hydrologic hydrology,
morphic, ecologic.

So this kind of a crash course
in fluvial geomorphology.

And again, the first and least
a good introductory text.

Recall from Module one,
also, the principles.

Principle two, that structure forces
complexity and builds resilience.

And in this example it's a beaver dam.

That's shown as that example.

So the best way, in my opinion, to
do this is to get out in the field.

There's just no substitute for it.

But, given that this
is a virtual workshop,

what you can do is
you can go to this link

and, you can watch the,
virtual field tour.

Just going to take
you there briefly.

In here, there's a map so you can
kind of, zoom in and around.

And indeed, if you...

If you zoom in, you're going to
start to see beaver dams.

Okay.

So that's, sort of helpful.

The red line is basically
a guided virtual tour, and

the yellow line is a self-guided
tour coming back down

The guided virtual tour,
there's a little introduction,

for what it is and
what it's about.

And then there's basically...

Some jerky GoPro feed

GOPRO: -- Mountain stream,
it's a single thread channel

here on Spawn Creek.
And I can see a little --

So it's really just me
explaining to you

if we were out in the field,
this is what we would do.

This is what we would look
for. This is how we would

read this riverscape.

And then the self-guided
tour is basically...

It's actually the same
river scape that,

coming down a slightly
different part of it.

And, with nothing more
than just the eyes.

So I don't talk at all.

And you can just, tally
off and make observations.

There's actually a little survey,
that you can take if you want.

There's also this drone footage,
which, just shows you this

river scape that we take
you on this virtual tour in.

Okay, so, that's kind of fun.

And, it's not as fun
as being in the field.

And there's some other
albums and resources,

some explanations
from Temple Fork.

There's things to go check out if
you want to go deeper, but

To just do the basic part you're
talking about, an hour and ten minute

video for the guided tour and a 20
minute video for the self-guided tour

Okay.

So you can do that
on your own time and...

Just to place this back,
where we're at here,

we're just kind of picking off
these questions one at a time

that relate to this more generic,

planning, portion of the
conservation planning process

[Loud horn blaring]

Umm, that was interesting.

So, anyhow, what,
one of the key questions,

this decision point really
is, it's a screening question.

Is the river scape structurally starved?

Because if it isn't, low tech
may not be appropriate.

There may be other things
that you might want to consider.

And so we want to
unpack that, okay?

We want to see, you know
in a situation like this

where it is a bowling alley
and there's, other than a

few cow pies, there's nothing
in it or in a bowling alley.

And other than a few short lived,
alder branches and boulders.

There's just not much in the
way of structural elements.

Okay

So we've talked a bunch about
this in the principles lecture.

We've revisited this, in Nick
Bouwes' lecture in module one.

And so this sort of pathway to complexity,

via structural forcing, that's
what we're trying to unpack.

And we're going to start with a little
elaboration of hydraulics, okay?

So hydraulics is...
[inaudible]

...is basically a function of climate,
hydrology, geology, geomorphology

But it's not those things.
Those things, are very

important deciding factors.

So it doesn't equal those things.
What does it equal?

Well, there's some hints on the screen.

We'll start with thinking about what
a hydraulic versus a hydrologic model is.

A hydraulic model takes in a
boundary condition, topography.

Right?

So you give it a river scape basically,
and you feed it discharge at the top.

You feed it a flow rate and then
it routes that flow rate through

and in so doing solves for
the hydraulics, which are the

primary hydraulic variables
of velocity and depth.

And so right here, we can
see in color, water depth.

Right?

The darker blues are deeper.
Same over here.

And we can see in this rainbow of colors
here, that's the magnitude of velocity.

And those are flow vectors.

And then this little animation
is just showing these things.

And so right now you've got this
flow coming in, on this inside bend.

Then there's a flow separation.

That separation is strong enough
to produce a shear zone,

a flow separation point that
then we have this little eddy.

Okay. And so...

... when you read a river,
the hydraulics matter.

They matter whether or
not you're a fly fisherman,

whether or not you're
a whitewater kayaker,

fluvial geomorphologist,
or an LTPBR designer

Okay?

You know, this is not out
of any sort of design manual,

or out of any sort
of hydraulics, right?

This is like basically,
a guidebook for boaters.

Right?

So it's telling them, okay,
well, you know, flows

coming in this way, you know,
look for, the seam, right?

This seam where two current speeds meet,
look for this slow water behind the walk.

Look for this faster water.

Look for this slow water
in an eddy, okay?

So let's unpack some of this,
this skill of reading water.

If you're a fly fisherman, you
probably, or a fly fisherwoman,

You probably know
exactly where to cast.

Right on the edge of those
seams, where the fish may

be hanging out in the,
it's just like this kayaker

is in this low energy, sort of,
eddy behind this boulder

and not over in the swift water, right?
So they can conserve energy.

And then if they need to
peel out and get back

into the current, they
can do that right away.

Fish do the same thing, conserving
energy right along that zone.

Especially visual drift
feeders, like trout.

Okay?

So some definitions for you:

This diagram on the left, just so
we know what we're looking at.

This is a plan four map.

This is a hydraulic model output.

It has two pieces to it.

It has in dark blue, this shade of
blue corresponds to water depth

And then the rainbow of colors,
and the arrows, and the

size of the arrows represent
the magnitude of velocity.

And then the arrows are pointing
in the direction of flow.

You have a boulder up here,
which, is this boulder right there.

Okay?

And there's a boulder that's
that's completely,

protruding out of the water
and there's one that's slightly submerged

and flows going over the top.
And that's what's shown here.

These two boulders are down here.

Okay.

And so you've got this flow coming along,
and those two boulders

are both out of the water,
and you get this, flow separation point.

Okay.

And so we call,

these boulders are examples
of structural elements.

A structural element
is any discrete object

that directly influence hydraulics.

And so in this case,
you have this flow separation.

The strength of that flow separation
creates creates this seam.

And within it, it's
such a strong flow separation.

That on the other side of this seam
we actually have flow reversal.

So we have an eddy.

So this, this sort of,
whirlpool like, pattern.

This is because at that flow separation
point, the magnet to the velocity

going past
it is so strong that shearing motion,

it creates, this really, strong, shear
zone.

And Eddy now notice this one.

The arrows are all pointing
in the same direction.

So this is this one coming right over this
rock.

There's a little, submerged
hydraulic jump, right over the top of it.

And then this is what we'd call a wake.

So an eddy versus a wake is really just,
two different shear zones,

but describing the difference between one
that just slows water downstream of it.

That flow separation isn't strong enough,

versus one that it actually,

flows in the opposite direction.

So structure elements can produce,

the stars, these flow separation points.

We also have some along the margins here.

So they can be produced by other features
as well.

Downstream of those flow separations,
you get seams

inside the seam, you get a shear zone,

and then you have some sort of
usually it's not as well defined

as the separation,
but some sort of re-attach point or zone.

And by mapping and identifying

these things, you're helping predict zones
where you might have erosion

deposition, margins
and force to morphic units.

So this is a really powerful skill
to be able to just read water like this.

It helps you recognize
what structural forces is doing.

Now, a big caveat.

You can get really good
at snapshots of reading river scapes.

You can get really good.

But bear in mind,

most of the time when you're looking
at a river scape, it's at low flow.

So the art is inferring,

whether those patterns exist
at higher flows

which may be capable of moving sediment,
moving wood, etc..

Right now it's wonderful

if you can get out at high flows
and see that you can't always.

And so that's where some of the art

of interpreting these things
or investigating them.

Post-Flood and starting to learn,

how, how these things act at higher flows.

So specific examples of structural
forcing,

shunting, constricting, splitting, slowing
down, backing up.

We've mentioned those things. Okay.

I'm going to show you three slides
that are horrendous.

They're out of,
this paper that I've mentioned before,

fluvial taxonomy.

And, they basically
there's just a simple way

that looks at differentiating
structural elements.

You don't have to use this,
but it might just be helpful

for helping you appreciate
how many things are out there.

The first split is whether we're dealing
with anthropogenic or natural.

And so,
you know, the things that you build,

in a river scape, the structural elements
that you put in, those are anthropogenic.

They may get co-opted and used
by the system, but they are anthropogenic.

The things that you may find
naturally occurring.

Those would be,

either of sort of an organic, origin.

So aquatic veg, beaver
dams, debris, largely debris, riparian

vegetation, roots, undercuts or inorganic
like bedrock and boulders.

Once you've kind of identified
those types, then it's helpful.

You can come up with whatever
the specific thing is

by using these key
attributes to differentiate it.

So we have the orientation.

Is it a diagonal feature.

Is it transverse across the channels
at stream wise oriented with it.

We have the position.

Is it margin attached.

Is it or bank attached.

Is it still spanning mid channel side
channel floodplain.

We also have the obstruction type.

Is it a sieve.

Is it a complete barrier
or porous barrier.

Deformable barrier.

What stages.

It has hydraulic purchase at.

So even at bank flow or just in floods.

And then if it is a structure element,
it's going to produce a shear zone.

It's going to it's
going to do one of these things right.

Shunt, constrict, split,
slow down back up and downstream of it.

It ought to have shear zone.

And so that would be a wake or neti
or if it goes right over

the top, could be a hydraulic jump. Okay.

So this table elaborates
what those things mean okay.

In terms of those differentiating things.

And then this table which you can't read
just breaks out some specific examples

of the many, many different flavors
of structural elements.

Again, we're just focusing on

beaver dams and what accumulation.

But recognize that this is
that there are tons of examples

of these both naturally
and anthropogenic occurring.

So back to something we've talked about.

What accumulation would

accumulation
simulated mimicked with paddles.

Right.

And so we have a margin attached power.

We have a mid channel town,
we have a debris jam or cartoons

out of the Asotin, which you heard,
Steve, talk about in module two.

And, these are cartoons that recapture,

and so you have velocity

hypothesized, velocity vector responses.

So those are hydraulic responses, right?

Shown with these arrows
where the structure is expected.

In the case of this one,
to create a constriction jet,

that jet,
kind of like your thumb on a garden

hose, will be maintained depending
on the flow rate for some distance.

And then it loses its energy.

And so as it does
that, it starts to spread out.

This would
be where your flow separation point is.

This would be your seen high flows.

You might have a pore over
over the top of the structure.

You might also get a little area up here.

And so those are your hydraulic responses.

Your hypothesized geomorphology
responses are shown.

With the colors you might get
a little bit of bank erosion here right.

This boulder is is helping maintain
that constriction jet.

If it wasn't there you might get more bank
erosion.

This the fact that you have a jet
and then it expands,

you might get a riffle, downstream of it
building up.

You might get some over bank deposition.

You might get,

scour of a pool, etc..

Right.

And so we get different responses expected
with these different, structure types.

This is the information
at a structure scale.

So when we get into module four
that you're using to read the river scape

for opportunities and think about how
that structural element

will engage at different flows.

So some of those hydraulic responses
are immediate at low flow.

Some are

you could you could make these predictions
for a typical flood.

Right.

And so we've got a bunch of sort
of cartoon versions of this schematic,

if you will, that represent
hypothesized responses

so that you don't need to draw
one of these things every single time.

Okay.

If you come up with a different sort
of structure design.

Yeah, you can make the cartoon ones,
but it's

think of it as like a standard detail.

Like if you're going to build a brick
wall, you don't need to draw a,

you know, a plan for every single brick
and exactly how that brick is installed.

What you need to do
is have a standard detail of what

a brick looks like,
and then you can move on with life.

Okay. So,

Yeah,
I think that's that's good enough for now.

So back to this question.

The screening question is your river scape
structurally starved?

Well,
we can go to some arbitrary river scape.

Here's one
that we're going to use this afternoon.

As our example.

And we could ask is it
is it structurally starved.

Well, it's helpful
to break this out by process.

So is it starved of wood accumulations?

Well, this is a classic oat

e problem observed to expected.

The easy part is counting whether or not
there's any wood accumulations.

The hard part is, contextualizing that

whether or not you would expect there
to be in that environment.

But if you just ask
if it's structurally starved,

it needs to be
it needs to be contextualized

with the expectation of what
you might have expected there.

I reviewed in module two.

Well, review is an overstatement.

I highlighted some of the wet debris
literature that can give you

some hints at this at terms of the
expected part of the problem.

But, you know, it doesn't take,

it doesn't take
a, you know, PhD in fluvial geomorphology

to look at a system
with absolutely no wood and recognize

that some wood would have been present
and, recognize a departure.

Okay.

Same thing for starved from beaver dam
activity.

Right?

You can count beaver dams,
but what's its capacity?

And we do have,
you know, models like Bratt

Beaver
dam restoration assessment tool, which,

allow predictions of existing

capacity, and capacities, not upper limit.

You know, in certain points in time,
it may reach

that capacity shouldn't exceed it.

It may get to some proportion of it.

But, they help provide
some bounds on that.

Okay.

So you want to look for evidence of woody
veg would be there to support

these processes that could be recruited
from either flood plains or hill slopes.

And look at current conditions
that might limit that.

Right.

And so I want to close this section out

with a short little exercise.

And that exercise is as follows.

What you need to do is,

open up your favorite mapping software.

To keep it easy,
I'm just going to have you use,

my maps google.com.

Right.

And you can go in
and you can create a new map.

And what you can do is, search
for that creek we're just looking at.

It's called the, Coburn Creek. Copy.

You are in it's in Wyoming. Okay.

There's actually Kovan Creek Road,
which is exactly where I want to take you.

Right.

So and then you can change this
to aerial photography.

And then you're going to create

layer
and you're just going to start mapping.

So I'm going to illustrate this for you.

I'd like you to find
at least five beaver dams.

And you can do this in any river scape.

So if I come over here

I go to my maps dot google.com.

Again you can see I actually
have one there, but I'll just show you.

Anyway, I'm going to create a new map.

Beaver dam demo.

And first thing I'm going to do

is change it to satellite imagery.

And I'm going to search for that creek.

Coburn.

Coburn Creek.

Oh, I am coming. Creek road.

Okay.

Took me right there, put a little pushpin
on it and even added that to my map.

It's already got an untitled layer,
so I can just call this,

you know, Beaver Dam map.

Of Beaver Dam.

So I should say it's a layer.

And, look at that.

There's actually a few just right here.

Yeah.

So I can then go to add

places, by importing data or by drawing.

Well, here's drawing tools.

So if you wanted to draw a beaver
dam crest.

That's one right there. So,

beaver dam, crest rate save.

And look at that.
It gave me a measurement.

It's 58ft. Okay.

If I wanted to, map out

a, you know, a pond,
it looks like I've got a crest down here.

Something like that.

Maybe,

crest two, you know,
and you can have notes.

You can even put a little photo.

Associated with that 177ft.

You can also, I thought there was,

Oh, yeah.

They don't have polygons right here.
Look at that.

It's a little overflow channel.

This one looks like it's groundwater fed.

Might be might be some in here.

It looks like there's.

This is, obviously a picture at high flow.

You could also just map them as points.

Right. So there's the there's beaver dam.

There might be a breached one.

There, it looks like there
there's one that's backing

water up.

And this isn't, admittedly,
this place where I'm taking

you isn't the easiest place to see them,
but they're here.

You can see them. Right.

And so once you get that, you know, then
you can use some of these distance tools

and you can start doing things like,
you know, counting like how many,

how many beaver dams
per kilometer per mile am I dealing with?

Are they dams on the main and branch?

Here's that main branch in high flow.

Or are they dams off on the floodplain?

That, groundwater or sometimes along the
toe of the slopes that are spring seeps?

Okay.

So I'd like you to

go in this river scape
and just map at least five.

Okay.

You can go to any river scape.

You can play these games.

Doesn't mean that your river scape
will have wood or have beaver dams,

but this is the exercise.

So back to the, last slide here.

Let's,

that's
that's all we got in the virtual workshop.

We'll have a little Q&A on this. Okay.

So just an introduction to, structural
forcing and thinking about that,

reminder that the real substance of this
is getting out in the field and doing it.

There's a lot
you can do from a desktop, too.

So, have fun with it.