1. Raster/Map Algebra/Hydrology

2. Cell size of raster data

3. Raster Generalization
Largest share rule
Central point rule

4. Map Algebra/Raster Calculation
Example
Precipitation -
Losses (Evaporation, Infiltration) =
Runoff 5 2 3 4 7 6 - =
Cell by cell evaluation of mathematical functions

5. Cell based discharge mapping by accumulation of generated runoff
Radar Precipitation grid
Soil and land use grid
Runoff grid from raster calculator operations implementing runoff generation formula’s
Accumulation of runoff within watersheds

6. Calculation with consistent 100 m cell size grid
“precip100” - “infiltration”
Outputs are on 100 m grid as desired.
How were values obtained ?
1.8 2 2
1.75
1.775
1.5
1.6
1.55
1.3

7. 100 m cell size raster calculation
4 – = 1.8 4
3.1 5
3.55
4.275 6
5 – 3 = 2
6 – 4 = 2
3.55 – 1.8 = 1.75
1.8 2
1.75
1.775
1.5
1.6
1.55
1.3
4.275 – 2.5 = 1.775
5 – 3.5 = 1.5
3.1 – 1.5 = 1.6
100 m
2.2 3 4
3.5
2.5
2.7 2
1.5
1.8
3.55 – 2 = 1.55
4 – 2.7 = 1.3

8. Analysis of topographic surfaces represented by a Digital Elevation Model (DEM)
3-D detail of the Tongue river at the WY/Mont border from LIDAR.

9. The challenge of increasing Digital Elevation Model (DEM) resolution
1980’s DMA 90 m
102 cells/km2
1990’s USGS DEM 30 m
103 cells/km2
2000’s NED m
104 cells/km2
2010’s LIDAR ~1 m
106 cells/km2

10. Data Conversion Tool

11. Topographic Slope

12. Hydrologic Slope (Flow Direction Tool) - Direction of Steepest Descent30 30 80 74 63 69 67 56 60 52 48 80 74 63 69 67 56 60 52 48
Slope:

13. Eight Direction Pour Point Model32 16 8 64 4
128 1 2
ESRI Direction encoding

14. Map Algebra Tool

15. Hydrology / Flow Direction Tool

16. Hydrology / Flow Accumulation Tool