GIS Applications in Watershed Analysis …..the watershed unit Dr. Dennis L. Johnson Assistant Professor Michigan Technological University COMET Hydrometeorology 99-2 Friday, 25 June 1999

DLJ 99 - Juniata College 2 Today’s Purpose Introduce the Concepts of a GIS Applications of a GIS Focus on the Watershed Unit …. Get you thinking …...

DLJ 99 - Juniata College 3 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”

DLJ 99 - Juniata College 4 Georegistered ? Representing a curved surface in a flat plane Locating that plane on the earth 3 issues –sphere –datum –projection

DLJ 99 - Juniata College 5 Sphere & Datum Mathematically describe a sphere Lock it down by making it touch the earth somewhere NAD27- Kansas Use satellites in modern day NAD83

DLJ 99 - Juniata College 6 Project to a Flat Surface Touches at the equator Touches at 2 lines of latitude

DLJ 99 - Juniata College 7 Unwrap the Cylinder One cylinder for each data layer Represent the data electronically A GIS!!!

DLJ 99 - Juniata College 8 GIS Layers

DLJ 99 - Juniata College 9 A 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.

DLJ 99 - Juniata College 10 Create A DEM from a Topographic Map

DLJ 99 - Juniata College 11 A Bunch of Blocks to Represent the Earth

DLJ 99 - Juniata College 12 A DEM What the Computer Sees & What You See

DLJ 99 - Juniata College 13 Other Views

DLJ 99 - Juniata College 14 Assign Flow Directions

DLJ 99 - Juniata College 15 Our Simple Area

DLJ 99 - Juniata College 16 Each 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.

DLJ 99 - Juniata College 17 Our Flow Accumulation

DLJ 99 - Juniata College 18 Let’s Look at an Example

DLJ 99 - Juniata College 19 Add Rivers Juniata College

DLJ 99 - Juniata College 20 Zoom In

DLJ 99 - Juniata College 21 Assign Flow Directions

DLJ 99 - Juniata College 22 Calculate Flow Accumulations

DLJ 99 - Juniata College 23 Overlay Streams

DLJ 99 - Juniata College 24 Let’s Delineate a Watershed Just Below Raystown Lake (dam)

DLJ 99 - Juniata College 25 Delineate Raystown Lake

DLJ 99 - Juniata College 26 Another View

DLJ 99 - Juniata College 27 Isolate Raystown Lake

DLJ 99 - Juniata College 28 Flow Directions in Raystown Watershed

DLJ 99 - Juniata College 29 South Facing Slopes

DLJ 99 - Juniata College 30 Buffer the Streams ~100m

DLJ 99 - Juniata College 31 Find South Faces < 100m from Stream

DLJ 99 - Juniata College 32 DEM

DLJ 99 - Juniata College 33 Flow Direction

DLJ 99 - Juniata College 34 Slope

DLJ 99 - Juniata College 35 Stream Delineation

DLJ 99 - Juniata College 36 K Values K = 0.48 K = 1.2 K = 2.1

DLJ 99 - Juniata College 37 Velocity V = KS 1/2

DLJ 99 - Juniata College 38 Flow Length

DLJ 99 - Juniata College 39 Advantages of GIS Time Savings Replication -Precision not Accuracy!!! Ancillary Data Data Reuses

DLJ 99 - Juniata College 40 Lake Superior SWE U.S. Army Corps of Engineers Manage Lake Superior Sault Ste. Marie Locks Snowfall is major contributor

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