USGS Multimedia Gallery: (Video)--Understanding Drainage Systems

Hello, my name is David Anderson, welcome to

understanding drainage systems. I work as the Partner

Support for Region 6 which is the Northeast of the

United States for the National Geospatial Technical

Operations Center in Rolla Missouri. There are many

types of drainage systems that are natural and

dendritic is the most common and that is what you are

going to see today as far as what is contained in the

NHD. They basically are derived from topology of the area, geology, flow of water, and

other items. The NHD allows end users to visualize

these systems almost immediately in most cases and be

able to determine what size of the area is being

drained by these surface water features. This is a

dentritic system that is being shown here. You can see

it looks kind of link a chain of features going down

into the one pour point which is that green dot up

there next to the lake in the Upper Northeast area.

And this is the most common of the drainage systems.

Interbasin connections can either be natural or

man-made. Karst systems are one of the most common

natural ones. They consist of things like sink holes

and springs where the water might disappear into a

groundwater system and then emerge eventually out into

another area. Man-made systems are quite common too

because of our public water drinking systems, ditches

and canals that are meant to re-route any of the

external waters to another area. One of the big ones

is Harold D. Roberts Aqueduct off the Dillon Reservoir

to Denver, or the Catskill Aqueduct off of the Ashokan

Reservoir in New York City that are used for public

water systems. Drainage basins as far as what is the

area of drainage is contained in the NHD and the WBD

features set. These are what some people like to call

hydrologic units and there are three populated feature

classes within the WBD. At the 8-digit, 10-digit, and

12-digit HUC systems. These are basically the

Subbasins, Watersheds, and Subwatersheds that are

populated. If you want to find out where the water is

coming from or how it is getting to an area, you can

use Utility Network Analyst. There are different flags

you can use such as starts, stops, things like that

that you can trace. In this screen-shot I am showing

that you can actually trace the flow uphill and you

will notice that the flow actually extends beyond the

little green flags which is the start and stop of the

Network Utility Analyst and that is because what it is

doing is identifying the whole feature where that

drainage is coming from. So this is how you would use

Utility Network Analyst to map the flow of a specific

area that you want to look at.