Terrain Modeling:

How to delineate a watershed using a printed topographical map

See NRCS handout: How to Read a Topographic Map and Delineate a Watershed

Mark the outlet (circle); Mark the high points adjacent to the stream or lake (“x’s”)

Starting at the circle , draw a line connecting the “x's" along one side of the waterbody . This line should always cross the contours at right angles (i.e. it should be perpendicular to each contour line it crosses).

Practice Exercises; Watershed & Lakeshed Delineation

Follow the steps just discussed:

•Mark the outlet•Mark the high points adjacent to the water body•Connect the marks; always cross a contour line at right angle (perpendicular).

Delineating Exercise 1

Start with a “lakeshed”; the land area contributing (draining) to a lake.

The lake is Four Point Lake in Cass County, near Hackensack, Minnesota

ADD OUTLET

MARK HIGH POINTS NEAR LAKE

CONNECT THE MARKS

Delineating Exercise 2

A watershed of a stream.

The small stream south of the Kadunce River, near Covill (just north of Grand Marais) in Cook County.

ADD OUTLET

MARK HIGH POINTS NEAR StREAM

CONNECT THE MARKS

Remember contour lines often point up stream; so near outlet make sure you don’t include other near by very small streams

Lab 11

Terrain AnalysisBrush Valley Creek

Data, Instructions,& Videos on FR website

Brush Valley Creek, Houston Country, MN

Lab 11Two .pdf maps to turn in via WebVista

Pay careful attention to where you create your output files

Watch the File Names

Write them down as you create them

3D Analyst

Hillshade

Viewshed

1. Fill2. Flow Direction3. Flow Accumulation4. Snap Pour Point5. Watershed

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23

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