gis applications in watershed analysis …..the watershed unit dr. dennis l. johnson assistant...

GIS Applications in Watershed AnalysisGIS Applications in Watershed Analysis…..the watershed unit…..the watershed unit

Dr. Dennis L. JohnsonAssistant Professor

Michigan Technological UniversityCOMET Hydrometeorology 99-2

Friday, 25 June 1999

DLJ 99 - Juniata College2

Today’s PurposeToday’s Purpose

• Introduce the Concepts of a GIS• Applications of a GIS• Focus on the Watershed Unit• …. Get you thinking …...


What is a GIS ?What is a GIS ?

• A GIS is a Geographical Information System• A series of data layers (maps) that represent

some feature on the earth’s surface• Ability to “overlay” !!

– All data is “georegistered”


Georegistered ?Georegistered ?

• Representing a curved surface in a flat plane

• Locating that plane on the earth

• 3 issues– sphere

– datum

– projection


Sphere & DatumSphere & Datum

Mathematically describe a sphere

Lock it down by making it touch the earth somewhere

NAD27- Kansas

Use satellites in modern dayNAD83


Project to a Flat SurfaceProject to a Flat Surface

Touches at the equator

Touches at 2 lines of latitude


Unwrap the CylinderUnwrap the Cylinder

One cylinder for each data layer

Represent the data electronically

A GIS!!!


GIS LayersGIS Layers


A DEMA DEM

• A Digital Elevation Model or DEM is used to represent the elevations of a section or area of land.

• The DEM is generally a gridded or raster data set.

• A raster data set means a series of rows and columns with each grid cell representing a property such as elevation.


Create A DEM from a Topographic MapCreate A DEM from a Topographic Map


A Bunch of Blocks to A Bunch of Blocks to

Represent the EarthRepresent the Earth


A DEMA DEMWhat the Computer Sees & What You SeeWhat the Computer Sees & What You See

778 765 750 740 747 759 765 766 769 776 786 795770 758 745 737 741 751 753 761 777 789 802 814777 763 747 736 735 743 750 767 787 806 820 832786 767 750 737 733 739 752 769 785 797 808 822791 773 756 741 733 733 744 759 772 779 789 806799 782 763 750 737 733 733 745 757 767 782 801802 788 771 761 751 736 733 738 751 764 779 798799 790 780 772 762 746 733 737 754 770 784 794811 799 787 771 757 741 728 730 745 765 779 783823 807 790 774 762 748 733 725 733 750 764 763830 814 801 787 776 761 743 728 725 737 748 751822 818 811 801 791 776 757 739 726 725 735 751

02

46

810

row0

24

68

10col

725

750

775

800

825

jen1_ele

740 760 780 800 820

jen1_ele


Other ViewsOther Views

0 2 4 6 8 10

0

2

4

6

8

10

col

row

740 760 780 800 820

jen1_ele

0 2 4 6 8 10

0

2

4

6

8

10

colrow

740 760 780 800 820

jen1_ele


Assign Flow DirectionsAssign Flow Directions

750 737 733761 751 736772 762 746

6 7 05 X 14 3 2


Our Simple AreaOur Simple Area

0 2 4 6 8 10

0

2

4

6

8

10

col

row

0 1 2 3 4 5 6 7

jen1_asp

6 7 05 X 14 3 2


Each Cell Flows Into AnotherEach Cell Flows Into Another

• Note that each grid cell flows into another grid cell and so forth.

• One could tally or keep track of the total number of grid cells that flow into each “downstream” grid cell.

• This is generally known as a flow accumulation data set.

0 0 00 2 10 2 8


Our Flow AccumulationOur Flow Accumulation

0 2 4 6 8 10

0

2

4

6

8

10

col

row

0 10 20 30 40 50 60 70 80 90

jen1_cou


Marfc10 - 144145 - 289290 - 434435 - 579580 - 724725 - 869870 - 10141015 - 11591160 - 13041305 - 1449No Data

N

EW

S

Let’s Look at an ExampleLet’s Look at an Example


Marfc10 - 144145 - 289290 - 434435 - 579580 - 724725 - 869870 - 10141015 - 11591160 - 13041305 - 1449No Data

Marfc_rf1

N

EW

S

Add RiversAdd Rivers

Juniata College


Juniata1_fill124 - 203204 - 282283 - 361362 - 440441 - 520521 - 599600 - 678679 - 757758 - 836837 - 916No Data

N

EW

S

Zoom InZoom In


Juniata1_dir1248163264128No Data

N

EW

S

Assign Flow DirectionsAssign Flow Directions


Juniata1_acc0 - 2525 - 9432.6679432.667 - 1414914149 - 18865.33318865.333 - 23581.66723581.667 - 2829828298 - 33014.33333014.333 - 37730.66737730.667 - 42447No Data

N

EW

S

Calculate Flow AccumulationsCalculate Flow Accumulations


Overlay StreamsOverlay Streams


Juniata1_str

N

EW

S



Juniata1_str

N

EW

S

Let’s Delineate a WatershedLet’s Delineate a Watershed

Just Below Raystown Lake (dam)


Delineate Raystown LakeDelineate Raystown Lake

Juniata1_fill124 - 212213 - 300301 - 388389 - 476477 - 564565 - 652653 - 740741 - 828829 - 916No Data

Raystown_wshdJuniata1_str

N

EW

S


Another ViewAnother View

N

EW

S


Raystown_dem211 - 289290 - 367368 - 446447 - 524525 - 602603 - 681682 - 759760 - 837838 - 916No Data

Raystown_str

N

EW

S

Isolate Raystown LakeIsolate Raystown Lake


Raystown_dir1248163264128No Data

N

EW

S

Flow Directions in Raystown WatershedFlow Directions in Raystown Watershed

32 64 128

16 X 1

8 4 2


Rt_south01No Data

N

EW

S

South Facing SlopesSouth Facing Slopes


Buffer the Streams ~100mBuffer the Streams ~100m

Raystown_dem211 - 289290 - 367368 - 446447 - 524525 - 602603 - 681682 - 759760 - 837838 - 916No Data

Raystown_bufRaystown_str

N

EW

S


Find South Faces < 100m from StreamFind South Faces < 100m from Stream

Raystown_str

Final21No Data

Raystown_wshd

N

EW

S


DEM


Flow Direction6 7 05 X 14 3 2


Slope


Stream Delineation

36DLJ 99 - Juniata College

K Values

K = 0.48K = 1.2

K = 2.1


Velocity

V = KS1/2


Flow Length


Advantages of GIS

• Time Savings

• Replication -Precision not Accuracy!!!

• Ancillary Data

• Data Reuses


Lake Superior SWELake Superior SWE

• U.S. Army Corps of Engineers

• Manage Lake Superior

• Sault Ste. Marie Locks

• Snowfall is major contributor

gis applications in watershed analysis …..the watershed unit dr. dennis l. johnson assistant...

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