Al ReaAll right.
So hi, everybody.
This is Al Rea, and this is
the USGS Hydrography Advisory
Call,
and we'll ...
Today, our guest speaker
is going to be Ryan Thompson,
and he's going to talk about
Selective Drainage
Toolbox
that he's been using,
and I think we've got
the main developer,
Curtis Price, is also on
as well to talk about this,
so this is a tool
that's used with lidar data
to make a good,
well-behaved lidar surface,
and I think ...
Did we have any announcements,
Becci or anyone else
at the USGS crew?
Did we have any announcements
we needed to make today?
Becci AndersonNot
that I can think of,
but if I come up with anything,
I'll add it at the end.
Al ReaYeah, okay, so, Ryan,
go ahead and take it away.
Ryan ThompsonOkay, thanks, Al.
As Al said, I'm Ryan Thompson,
and Curtis Price is also on.
We're in the Dakota Water
Science Center.
I'm in an office in Huron,
and Curtis is in Rapid City,
and we'll just have
a presentation today
that goes over a little bit
of a project-specific background
for the Selective Drainage
Toolbox
and then talk about using it
sort of in a generic sense,
and hopefully be able
to answer questions
as to if it might work
for your application.
Let's see, okay.
There we go, so I guess
what I'll be talking about
is the study that we had
in South Dakota
that sort of identified
the need for the tools,
a little bit about
the study area for that
and then also the methodology
that went into development
of the tools.
Go through
some of the processing
using the Selective
Drainage Toolbox
and how we reviewed
the potential culvert locations
that are identified and then
what we wanted to be able
to get out of it
as a science center
was to be able to refine
the watershed boundaries
and subdivide to 14 and 16-digit
units where appropriate.
I'll touch a little bit
on what some of the value
was for our cooperators,
and then we'll have a time
at the end for questions.
So the gist of it was that
we needed to identify a way
to kind of have
a standard methodology
for utilizing the lidar data
that we already had in place
in South Dakota,
and we didn't have
complete culvert inventories,
so we needed to be able
to identify locations
where the culverts were
and then hydro-enforce them
to get a culvert-aware
lidar-based DEM
that could be used
for resource management,
and then we'd refine
our watershed boundaries
with that and develop
a densified drainage network,
a few more lines than what
you can see in the NHD,
and, as I mentioned earlier,
to update with 14 and 16-digit
unit lines where appropriate
and then also explore seeing
if there's areas
where the NHD lines, flowlines,
might need
to be updated as well.
We had kind of a long list
of cooperators on this study,
and I won't go
a whole lot into it,
but the state
and local cooperators agreed
to do the ground truthing
of the culvert locations
that we came up with
through this Toolbox.
Some of them,
you could verify
that there was a culvert
there through imagery.
There was a lot
of other locations
that needed to either have field
verification of some sort
or use of
a different imagery set,
and I'll talk
a little bit about that,
but the cooperators agreed
to do that on their own,
with their own staff,
which made the project
a lot more affordable,
given that we didn't have
to go out
and do ground truthing
in the field.
So a little bit of background
on the project specific
to South Dakota,
I'll go over the location
of the study area
and kind of physiography there,
sort of a hydrography there,
the basis of the methodology
and then what we had
going into it for data.
You can see the study area
is that little red polygon
that's in the kind of the ...
near the southeast corner
of South Dakota,
and that pink-shaded area
is the Prairie Pothole Region,
and so you can see out
study area
is kind of on the edge
of the Prairie Pothole Region,
and that's characterized
by poorly developed drainage.
There's not a well-defined
stream network
in a lot of those locations,
so a lot of wetlands
and sloughs,
and that was the area that was
looking at contour lines
on a 1:24,000 map.
It's not necessarily
always very evident
where or what direction water
is going to flow
when those splatter areas,
so this is kind of a concern
of some of the co-operators.
They needed to worry about
expanding the urban areas
and developing into the areas
that are currently ag now,
and this was just
going to be a tool
that made that possible
for them.
Actually, let me back up here.
I guess you can see
part of the study area
does have a fairly
defined stream network.
It's mainly in South Dakota
and a few of
the different counties there.
Part of it did spill over
into Minnesota and Iowa.
As sort of the southwestern edge
of the study area,
that's where it gets into
that Prairie Pothole
kind of a topographic setting,
and where it was
a little bit more critical
to have the lidar data there.
The basis for the tool,
it builds on
the Selective Drainage methods
that were pioneered
by Sandra Poppenga,
Bruce Worstell, Jason Stoker
and Susan Greenlee at EROS,
and they published
that in the SIR there,
and then Curtis kind of expanded
on that in building the Toolbox.
The gist of it
is that most of the time
when we are delivered
lidar-based
digital elevation model,
it's typically a bare-earth
type of product,
and from what
my understanding is,
a lot of the contracts
are written such that bridges,
or at least bridges larger
than a certain size,
need to be hydro-enforced,
so the bridge deck
will be removed
and the surface will
actually reflect the channel,
but culverts oftentimes
are not hydro-enforced,
or at least not all culverts
will be hydro-enforced,
so if you model run-off
over a surface
that does not have
hydro-enforced culverts,
basically the roadbeds,
or railroad grades
or other built infrastructure
is going to act as a dam.
The lidar returns are going
to be off the crown of the road,
in the ditch slope,
but the DEM has no way to know
that water can pass through
that culvert
until you hydro-enforce it.
So the ...
Kind of putting it
into a little flow chart,
we start out
with an elevation model.
You can fill that
to get a ...
generate a flow direction,
flow-accumulation grids.
Once you filled it, you can get
a fill-difference grid
that kind of comes into play.
From the fill-difference grid,
you can come up
with the filled areas,
and when you intersect
the filled areas
with the highest
flow accumulation cells,
that will tell you
where the pour point is for
when that fill area begins
to spill and contribute drainage
to the adjacent
topography again.
From the filled area,
you can also go ...
Using this tool,
you can sort of use
the Selective Drainage methods
and identify areas where
culverts need to be burned in,
then you can actually
burn those in and feedback
through the beginning
of the loop
and do this
in an iterative manner,
and if you do know some of your
culvert locations prior to this,
you can certainly burn
those in at the top,
and that will get you
part of the way there,
and the tools should help you
identify the remaining
culvert location.
Though, here's just an example
from our study area.
You can see in the aerial image
on the left,
we have a stream that flows
roughly north to south,
or top to bottom.
You can see the culvert
going underneath the ...
It's a gravel road there,
a township road,
and it's obvious in imagery,
but the ...
In the DEM, it does not know
that's there,
so it's going to just act
as a dam on the left here.
In this image, the pale blue
kind of transparent area
represents the fill area
where the water
would basically pile up
on the upstream side of the road
until it hits an elevation
such that
it can finally
overtop the road.
And the low point
in the crown of the road,
in this case, is a little bit
to the left of the culvert,
but it's not too far off,
so in this case,
it didn't change
the flow path a great deal,
but if you digitize a line
where that culvert is
and higher enforce it
or, effectively,
just trench through the road
at the location of the culvert,
you can rerun your flow
accumulation flow direction
and generate your streamlines,
then you're going
to get streamlines
that match up a lot better
with what you actually
have going on in the field.
As far as the data that was
available in our study area,
quite a bit of Eastern
South Dakota was available.
We had lidar-based elevation
in the NED for South Dakota.
Across the border
in Iowa and Minnesota,
there was similar
vintage lidar data,
but it was in a state-maintained
product and not in the NED.
Additionally, Sioux Falls,
for those of you not familiar,
Sioux Falls is the biggest city
within our state
that was within
the study area,
and they had
a 2012 lidar acquisition
to kind of update
some of the areas
that they're expanding into,
and they wanted us to be able
to use the 2012 data
where it was available
and then use the 2008 data
surrounding
that where it was not.
Additionally, there is
Pictometry imagery available
for Lincoln and Minnehaha
counties in South Dakota,
and Pictometry is an oblique
aerial imagery
that, in this case,
had a 3-inch pixel size,
very high resolution.
Because it's oblique,
you can look at things
from different angles,
and that proved really,
really helpful in confirming
culverts at different locations,
and we'll see some of that
imagery in slides coming up.
Also, we had some
culvert data available
going into the project.
There was an inventory
that contained culverts,
but only if they were 30 inches
and larger on state
and city highways.
The city of Sioux Falls
had a GIS of their storm
water system,
and culverts were in there.
They weren't necessarily in a
feature data set by themselves,
so we kind of had to pick
those out from the rest,
but we were able
to use that information.
Also on county highways
in Minnehaha county,
there was inventory for culverts
30 inches and larger,
and then throughout
the project,
culverts on county roads within
Lincoln county were inventoried,
and then also
some of the culverts
on local and township roads
in Minnehaha County
were inventoried,
but our tool was able to find
a lot more culverts
that couldn't be
identified in the field
because it got late
enough in the summer
that the grass grew up,
and it was just very difficult
to see well enough
to find them all.
So the ...
I guess we mentioned earlier,
the Toolbox was developed
by Curtis Price.
It was released on ScienceBase
last September.
At that time,
we were at ArcGIS 10.4.
I wrote up a little bit
of a user guide
that's available
to go with it,
and then currently,
we're in the process of updating
to make the toolbox compatible
with ArcGIS 10.6 and also Pro,
and we're hoping to be
able to release that here
within the next
maybe month or two.
And if you search for Selective
Drainage Toolbox on ScienceBase,
I'm pretty sure
that will come up.
Although, I think there's a link
for the ScienceBase page
in the meeting announcement
today, or the call announcement.
So once you've downloaded
the Selective Drainage Toolbox,
it's going to look kind of
like that screen capture there
on the right.
There's a little bit
of a utility tool in there,
in case if you need
to start with,
let's say, a LAS file,
and you're working with points
rather than
a raster product already.
Tools one, two and three
are included
in the global tool as well.
I guess in the workflow
that I've kind of settled in on,
I tend to run those
tools consecutively
more often
than using the global tool,
and then tools four and five
are used to enforce the culverts
and then evaluate
the identified culverts.
If you download this
and some of the tools
are showing up for you,
it may be because an extension
that they need
has not been enabled
in your settings within ArcMap,
so that's something
to keep in mind.
We've run into that before.
There's kind of some terminology
that might be helpful
for you to know
going into using it.
Drain line is the name
that we've given
to potential culvert locations
that the tool identifies.
There's also a search distance
that the user can specify,
and that's basically
the maximum distance
that you want to allow
between the minimum point
associated with a particular
fill polygon
and the end point
of its potential drain line
or culvert
that the tool will find.
You can also specify maximum and
minimum culvert-fill-zone areas,
and that's useful for
if you're in a setting
that has natural lakes,
you can use the height,
the max filter,
to make sure the tool
isn't wasting time
trying to drain your lake
with a culvert
if it's actually a lake
on the landscape,
and, likewise, you can specify
a minimum size
that the tool doesn't need
to be concerned with,
and that way you don't
identify a culvert
for every little puddle
on the sidewalk.
There's also a ...
pour-point distance is a term
that is kind of
the maximum length
that you want to allow
for the drain line
or the culvert features,
and then the tool
was set up to run iteratively,
and that was so that ...
In some cases, there's going
to be more than one culvert
that fall within the extent
of a given fill-area polygon.
Sometimes there is a culvert
and a relief culvert nearby,
or that kind of a situation,
and the iterations
help identify multiples.
So this is ...
We'll kind of go
through a sequence of slides
that just shows what the menus
are going to look like
when you open it up.
There is, if you show help,
there's going to be a little bit
of help on the sidebar
on the right there,
and then as you click
into each one of these fields,
there will be a description
that hopefully will clear up
questions you might have there,
but for tool one, basically,
you enter the elevation raster
that you're starting
your work with,
and then populate the name and
path for the output fill raster,
the flow direction
and flow accumulation.
You can also give a name,
assign a name,
to a different raster,
and fill-line rasters and
specify a minimum area there.
The minimum area can be
specified either in cells,
depending on what
your resolution is,
or you can specify it
in terms of just an area.
Tool two, basically,
it takes the fill zones
that are going to be built
in the first step,
and it comes up with
some extra information for them
that's needed
for subsequent steps,
so you have
your elevation raster,
and fill raster and flow
direction, flow accumulation.
From the fill-zone raster,
it's going to make polygons
of those fill areas.
I'd mentioned earlier that it
intersects the fill areas
with the flow accumulation grid
to identify the pour-point cell,
the cell with the highest
flow accumulation value,
and then also the minimum
elevation point
within that fill zone,
and here, again,
you can specify a minimum area
that you want it
to be concerned with.
Tool number three is creating
the selective
drainage flowlines,
so the input point
is the minimum point
that we found
in the earlier step,
and the fill-zone raster,
elevation raster,
and then the output
flowpath line
is just what you want it
to name the file
that it's still going into these
potential culvert locations,
and here's where you can
specify the search distance
for how far you want
to allow it to look for the ...
Basically, the cell
on the other side of the road,
that is, is what we're looking
for there, so if you have ...
If you're working in an area
that primarily
is two-lane roads,
that's going to be a ...
You'll be able to use
a shorter distance
than if you're in an area
that has multi-lane roads,
or for us, it's the interstate,
and you could do this in
multiple steps if you wanted to.
Once you've gone through ...
And we'll talk more about this
in slides coming up,
but once you've identified
your locations of your culverts,
this is a tool
that basically burns those in.
You can also specify lines
where you want it
to be walled up as well as just
having culverts burned in,
and that might be for
if you have a situation
where there are
either berms or levees
or some kind of a feature
that was either
added after your lidar data
was collected, or if it's a ...
We have a few locations
where there's kind of
a concrete flood wall
that's narrow enough that it may
not get picked up in lidar data,
but it could be
an important feature
that you want included
in your elevation raster.
There's also a field there where
you can specify sink points,
and you might find that useful
if there are something
like a quarry,
or gravel pits is something that
we run into in our study areas,
where, basically, it's sort of
like a non-contributing area.
A terminal lake is what
it's going to act like,
and that just allows ...
If you put a sink in there,
then it doesn't try and find
a culvert to drain that out
because, in a lot of cases,
there's ...
That'll be the lowest
elevation area around,
and you won't be able
to get it to drain.
And offset z-value is basically
how deeply you want
your culverts trenched,
in and how high you want
your walls built up there.
Tool number five is once
you've burned in your culverts,
then you'll want to rerun
the elevation derivatives to get
your updated flow accumulation,
flow direction grids.
Then this takes
those layers again
and builds a synthetic
drainage network,
and you can see from that little
snip of the table at the bottom,
Curtis has this set up so that
each stream reach is populated.
There's an attribute table
that's populated with the number
of cells that that
particular reach drains,
and also the area,
so once you get this layer out,
you can ...
If you're going to display
it in ArcMap,
you can change your symbology
depending on if you want to show
a very detailed, zoomed-in
sort of drainage network,
or if you want this more of
a broad-scale,
not-quite-so-much detailed.
And then I mentioned also,
there's the Global
Selective Drainage tool,
and this kind of is set up
so that it can run
the other tools consecutively.
Allows you to specify
the same kind of limits
we talked about earlier,
and then this is where
you can specify
if you want it to do
one iteration or three.
Let's see,
and I think the next ...
Yeah, we also put together
kind of
some tips for processing,
and depending
on what your DEM resolution is
and the size of your study area,
we found it really helpful
to run the tool on a subset
of the total study area,
rather than turning it
loose on it,
and having it crank away for
3 days or something like that.
It's a little bit more helpful
to have it just ...
if you specify an extent ...
and the tools that the Toolbox
uses will honor
a processing extent,
but not a processing mask,
so that's something
to keep in mind,
but if you can chunk it out
in sections,
that will get you
progress faster
than
if you give it one massive area
and make it process
all the way through that.
You can kind of do a little bit
of playing around to find out
what your optimal
processing area is,
and while you're doing that,
I'd suggest having it
just do one iteration
until you've kind of honed in
on what size
is going to complete
in a reasonable amount of time.
I'd also suggest having it
process, including in your DEM,
and area beyond what you expect
the study-area boundary to be,
so, for us,
we had the WBD lines
that were
based on the 1:24,000 contours,
and then we included a buffer
beyond that
just because we thought there
was a fairly high likelihood
that those boundaries
could change,
one way or the other,
based on culvert locations with
the high-resolution lidar data,
so we included a buffer there.
And as you develop
your layer of culverts,
I found it helpful to attribute
them to just kind of give ...
In our case,
it was for our own use
and also for the cooperators,
what we used to say,
"Yes or no, there is
or isn't a culvert there,"
so this is an example for that.
Basically, we went through and I
added a couple fields for if ...
Is it a good location?
Typically, you're going to find
a culvert going under a road,
but not in all cases,
we discovered,
but ... so if you have a ...
if the tool finds ...
has drawn a culvert line,
but it's in a depression
out in the middle of a field
and it's not even adjacent
to a road, then you could say,
"No, that's not
a good location."
We also did kind of
a preliminary check
within just ESRI basemap imagery
to see
if there was a culvert visible
within the imagery,
and if there was,
then we populated
that in that column as well.
And then I ...
Well, I guess we have another
slide coming up for Pictometry.
There's better imagery
out there now.
I've found that Google Maps
is actually
pretty good in a lot of areas,
and that works well
for just being able to look
and see if there's a culvert
in that location.
Curtis PriceYeah, I mentioned,
Ryan, we were using Street Map.
Ryan ThompsonYes, yeah,
that's also very helpful.
I'm not sure if all states
are that way,
but in South Dakota, there's,
at least on state highways,
there will even be a delineator
post in the ditch
to mark
where the end of the culvert
is for when the ditch gets mowed
and things like that,
and even if you can't see
the culvert itself,
if you can see the post
or there's kind of little cues
that you can tune in to
to help you decide
if there's
something there or not.
So the tool will come up with
these assumed culvert locations
or potential culvert locations,
and this is just
kind of going to go through
a couple examples of those.
Again, this is a stream
that flows roughly from the top
of the photo down to the bottom.
Went up against
a gravel road again,
so we have that pale blue area
is the fill zone,
and then the pale blue line
is the stream line
before the culvert
was hydro-enforced,
so you can see
we have a lot of the straight
and diagonal stream lines
going on there
in that fill area,
and in this case, the low point
in the crown of the road
was almost directly over
the location
of where that culvert is,
so the fact that
it spilled over the road
didn't change a lot of the path
of the main channel,
but once we did hydro-enforce
the culvert and rerun things,
we got a lot better set
of flowlines for the stream
once that fill area
was not there, impacting it.
We had other situations
where this is a similar deal.
This is actually a kind
of a draining canal,
following from north
to south again.
In this case,
the point where water would ...
It didn't overtop the load.
Instead, it overtopped
kind of a berm adjacent
to that drainage canal,
and then it flowed off
to the upper left
in that corner
of the image there,
so in this case, if we would not
have been able to ...
If we didn't know
that this culvert was there
and hydro-enforce it,
our stream network would have
been very much impacted.
This flowline
actually went over,
kept going to the west
in the section,
and then it ended up
dumping into a tributary
adjacent to the west,
so it can potentially make
a big difference if ...
That's really one of the ...
The pour point does not coincide
with where the culvert is
in the road.
We also had some things that
I didn't really expect to see,
but the tool was able to find.
If you look at that aerial image
on the left, you can see
that there's a fill area
that's kind of coinciding
with the old oxbow channel
of the Big Sioux River,
and there's definitely not
an obvious road there,
but it was identifying potential
culvert locations on the road,
and if you look to the DEM,
you could definitely see,
in fact, there was something
build across that oxbow,
and let's see,
I think it's the next slide.
This is that high-resolution
oblique imagery
that I mentioned,
and I'm not sure ...
If I mouse over the picture,
are you guys seeing
my mouse at all?
AttendeeYep.
Ryan ThompsonOkay, so where
that red arrow is,
this is actually the path
that we were seeing in the DEM,
where the farmer was ...
had that road to cross
that oxbow lake
to be able to get to fields
on the other side.
It's a little bit settled,
but if you have enough evidence,
you can find it.
Yeah, there has to be
culverts there.
There's a few other
interesting things
we were able to see
in looking through this.
Here is an example of something
that is not a culvert.
It's a depression
that's not adjacent to a road.
The red drain lines
the tool came up
with were not in locations
likely to be a culvert,
but in looking at that little X
as the minimum point
for that fill area,
we can see that ...
You can tell there was something
going on with ... in the field.
The farmer basically had to farm
around some object there,
and so what I'm thinking
this object is,
is the inlet for an
underground ag drainage system,
which I don't
want to oversell this,
but there's going to be times
when you can find things like
that, too,
that are helpful to know,
so if you were
going to model this,
you could actually
put a sink in there
and have that behave better
than running off.
And then as I mentioned,
one of the things we wanted
to be able to do with the tool
is update our WBD boundaries,
so in this slide,
you can see in green
the 12-digit HUC boundary
based on 1:24,000 contours,
and that's compared to
sort of the blue polygon
with the red boundary
of what we came up
with based on this lidar data.
For the most part,
there's pretty good agreement.
We can see one area right there,
where there's a little bit
of divergence.
Then when we looked
at that closer,
you could see that
there was actually the watershed
flooded up against a road there,
and so we
went back to the imagery
and looked at that again,
and within ...
This is ESRI basemap imagery.
There's nothing obviously ...
nothing in there
that screams culvert to me,
but if you go back
and look at it
with this Pictometry imagery
that I mentioned,
in here it becomes
very obviously that
there's the end of the culvert
in the ditch, so this was a spot
where we needed to hydro-enforce
one more culvert,
and then the boundary ...
rerun the elevation derivatives,
and the boundary
will adjust itself.
And then I guess
you could go through
and subdivide your 12-digit HUCs
into 14s and 16s,
if that's something that
is helpful to your cooperator.
So these slides were ones that,
when I originally did
this presentation,
the cooperator talked on,
so I'm kind of trying to go
from memory here,
but I know one of the ...
Some of the applications
that they used it
for was there were some areas
within their municipality
that had undergone
some development
prior to implementation
of their drainage ordinance,
so this helped them to kind of
know what was going on there.
They were able to ...for areas
that were slated
for development,
they were able to identify spots
that they could expect nuisance
ponding,
and maybe even specifically
suggest that,
"Hey, this is an area
that could be a good
stormwater retention area.
It's already low.
It's going to hold water
during certain times."
Just to help let developers know
where culverts were likely going
to be needed,
and what the drainage areas
were going to be for culverts
in new areas.
And I guess this was an example
they had put together of ...
You can kind of see the gray
crosshatch polygon there,
and that was area
that was identified
in a FEMA floodplain FIRM
map, but a landowner wanted
to be able
to put a storage building
on part of their lot,
even though it was in this
floodplain-designated area,
but with use of the selective
drainage tools,
they were able to see that ...
Let me see if I can get
the mouse there ...
that a corner of that lot
was actually high enough
that they could add
the storage building on there,
and it made the landowner happy,
and made the cooperator happy
to be able to help him as well.
I guess that's kind
of all I had,
but we definitely have time
for some questions
if anybody had some.
AttendeeI have a question.
Ryan ThompsonAnd Curtis is
on too,
so if you have questions
specifically to the nuts
and bolts
of authoring the tool itself,
he will be able to field
those as well.
Al ReaSo thanks a lot, Ryan.
I'll start off and ask ...
I know you've alluded to this
a couple of times,
but could you give us
some examples of what the ...
first of all,
what your DEM resolution was,
and then what size
of processing units
you ended up using
and what were your run times?
Ryan ThompsonSure, so the DEM
that we had to ...
I guess we went back
to the 1-meter source data,
but we actually did a little bit
of kind of
a sensitivity analysis,
and we took a small subset
of the area.
We went through all the steps,
and we ran and got sort of a ...
the synthetic flow network
when it was
at that 1-meter resolution.
Then we also redid it
when it was resampled to 2-meter
and 3-meter resolutions
and compared.
We actually went up
to 5-meter as well,
and sort of did a comparison
to see how much can we ...
how big a cell could we have
and still not lose accuracy?
And that was
the 3-meter cell size
is what we kind of
settled in on, or yeah.
Yeah, 3-meter cell size.
It was actually the city
wanted to work in English units,
so it was 10 feet
is what our cell size was.
I think initially
we started working ...
We kind of tried to keep
our processing units
to 12-digit
HUCs or smaller,
but because it's working
on an extent box
and not necessarily
an analysis mask,
sometimes we'd cheat
the boundaries to ...
just to get another ...
squeeze another one in there
and have the processing time
not take as long.
I think it was, the steps that
took the longest to run were:
Flow accumulation was one,
and then the step
where it's identifying
the potential culvert locations
was also one that it cranked
away at for quite a while,
and those often
would run overnight
and would be ready
the next morning,
or partway through
the next morning,
if I started those
in the afternoon the day before.
Did I catch all those out,
the questions you had?
Al ReaYeah. That was good,
so those were
kind of overnight runs,
and everything else
you could do in ...
Ryan ThompsonYeah.
Ryan Thompson... sort of ...
Curtis PriceScalability is,
of course,
a real issue
with these things, and ...
But the cooperator
originally is going,
"Well, we have
this 1-meter data,"
and I guess my point is,
is when you average
that out to 3-meter data,
you get really
good 3-meter data
because you've averaged out
all the artifacts, so it's ...
There's a lot of stuff in there
you see in the full resolution
that isn't really real
for this kind of analysis.
AttendeeHey, guys. This
is Sean Vaughn from Minnesota.
Ryan ThompsonMm-hmm?
AttendeeSo I understand
your methodology well.
It reflects a lot
of what we've done here.
I've been doing this type of
work for well over two decades.
Question specifically
is directed
towards your search tolerances.
In much of our experience,
when you're allowing
the algorithm
to search
and create that line, it ...
We sometimes get what
we would call here
a digital dam bridge line
that really isn't in exact
alignment with the culvert.
Did I miss something
in the presentation?
As I'm trying to think
back to it,
did you realign things,
or how did you maintain
more of a perpendicular
directionality for your lines?
>> So what I did
in my workflow is,
I would go through and review
these potential
culvert locations,
and rather than use
the drain line
that the tool came up with,
I used that as the basis for,
"Okay, that there's
a culvert somewhere here,
but I'm going to digitize
a line of my own
that I'll call the culvert,"
and then I could make it ...
Depending on if you had
evidence in imagery,
you could make it perpendicular
or a little bit diagonal,
but then you could get
the length of that culvert
a little bit more realistic.
The tool, you kind of have to
give it a long enough distance
so that it can get across
the road embankment,
in cases where the culvert
is not perpendicular,
but that kind of
has the side effect
that it may continue
the culvert farther
down the slope
than what an actual one would,
so I digitized my own layer
of the culverts
just to have a little bit
more control over that,
and then also attributed
those culverts as to,
"Is this one we could see
in the imagery,
or is it one that we just knew
it was there
because of looking at the" ...
If you can see a channel
on the upstream
or the downstream side
of the road,
but you can't see a culvert,
you can oftentimes be assured
that, well, there must be
a culvert there,
or sometimes you can see
evidence in imagery,
or sometimes you just have to
assume there's a culvert there
because there's not water
ponded up,
or you know that, well,
the township is not going
to put up with water
running over the road
every time it rains,
so there must be
a culvert there.
So yeah, I digitize
my own culverts,
and then attribute it as
to whether there was
evidence in imagery,
or if it was something
that was just kind of a,
"I presume
there's a culvert here."
AttendeeSure.
So I apologize if I missed that
level on that detail earlier.
One of the reasons
to flush that out
is because going back,
manually digitizing them
certainly does add to the time
commitment of this work,
and one thing a lot of us
in this meeting
tend to be aware of is just this
is very time-intensive work,
and you just really can't ...
It's always so hard to get away
from the human involvement.
You need human eyes on this
in reviewing it
so that we can ensure
that our flow paths exist
with a lot of
convenient features.
Ryan ThompsonTrue, and I guess
we were coming
at this kind of
from the flatland extreme.
As I mentioned, we had kind of
a part of our study area
was sort of
a Prairie Pothole environment,
so there we knew
there was going to be culverts
that were going to be
really critical.
If you're in a higher
relief environment, I ...
We haven't worked in a super
high-flow area yet,
but I presume that more
of your culvert lines
that the tool comes up with
are going to be found
basically right over ...
They're going to plot ...
The pour point is going to be
right over at the location
of the actual culvert location,
and it may be in an environment
like that,
you could get by
with less oversight.
If you ratcheted down
your culvert length,
you may be able
to get that to work
without having
to digitize things.
AttendeeSure.
Thanks for your response.
Ryan ThompsonYep.
Al ReaSo, Ryan, you mentioned
that your co-operators went out
then later, I guess,
to verify some of these?
Ryan ThompsonYeah.
Al ReaMaybe the ones that you
couldn't see in the photos,
or did you work that back
into a revision cycle?
Ryan ThompsonThere was kind of
a little bit
of iteration that way.
I guess we came up
with our layer of,
"Here is where we believe
the culverts are.
These are the ones
that we know are there."
Or, well,
and I guess in our case,
there was some
that were already inventoried.
They were a given. There were
some that were newly found
and confirmed through imagery,
and then there was some that
we just believed to be there,
so what they did
is they took that layer.
They would have their staff
check it again
with that Pictometry imagery
that I mentioned.
Depending on the time
of the year,
that imagery coincided with
if the grass was short
and you could get
an ideal angle.
A lot of times,
you could see the either
the ends of the culvert,
or at least a shadow where
the opening of the culvert was,
and then they could confirm
without actually having
to drive to the spot,
but there was some
number of culverts
that were a little bit
more critical,
that they couldn't
confirm with imagery,
that they did actually
do a field visit for,
but most of that was
a desk exercise, actually.
Al ReaOkay.
Al ReaMore questions
from anyone?
All right.
Well, Ryan, thank you again.
Thanks very much
for your presentation.
It was really interesting,
and then you will send out ...
Let's see, did you have the URL
where this tool is available?
We should ...
Ryan ThompsonI believe that's on
one of the slides, yeah.
Let me back up here.
Al ReaThere's something USGS
runs called ScienceBase,
and you can probably search
for ScienceBase
in Selective Drainage
and find it.
Ryan ThompsonRight, yup.
AttendeeI have a quick question.
This is Karen Adkins.
You mentioned that
you're upgrading to ArcGIS 10.6
and ArcGIS Pro.
Do you have an expected timeline
on that at this point?
Are you just getting started?
Ryan ThompsonWe're ...
I think there's just
one of the tools
that's not working in Pro,
or one of the steps in the
Toolbox is not working in Pro.
The rest are
all working in 10.6,
and I might have
to defer to Curtis
as to how much it's going
to take to tease out
what's going to work
in the Pro version,
but I guess I'm hoping
we can get that out in ...
within a month or two. Does that
seem reasonable, Curtis?
Curtis PriceYeah, it just had
a few little tools
that it had to do.
The Python code actually works
both ways pretty well.
The biggest issue we've had
has been the changes
in some of the raster tools
that ESRI has made in 10.5
and 10.6 that have
kind of changed
how temporary files
have been handled,
and it's been kind of a pain
for a lot of these applications,
and so we're quite willing
to hand out
if someone wants
to work with us
and try out one of these tools
in the newer version,
they're welcome to get
a hold of us.
AttendeeThat's excellent.
Al ReaIs the source code
available there
on ScienceBase as well?
Curtis PriceYeah, when you
download it,
it's all right there, yeah.
Al ReaIt's all there, so ...
Curtis PriceYeah.
Al ReaOkay.
Curtis PriceYou have toolboxes
and script folders,
and it's all in
a fully available package there.
Al ReaAnd it's Python, right?
Curtis PriceYeah.
It's all Python, yeah.
Al ReaOkay.
Curtis PricePython toolboxes,
PBX file,
and script files
and layer files,
and then the layer files
are set to symbology
and all that kind of stuff,
so it's all packaged
in a toolbox,
a folder with toolboxes
and stuff,
and the development has mostly
been done in Arc 10.6,
and then we save it back
to a previous version,
so there's a 10.4.1 version
toolbox.
You can read from 10.4,
or 10.5, or Pro or whatever.
You can always read forward.
You just can't go back.
Al ReaOkay.
Al ReaGreat, well, thanks again
to both Ryan and Curtis.
Were there
any last-minute announcements
from anyone on the USGS team?
Becci AndersonNope, not that
I can think of, Al.
Al ReaOkay, well, I think
we'll close then.
