Network Examples
• Distance to schools in Gambia
• Puerto Rico Streams
• Determine water availability for Nuclear Reactors in Russia
• Invasive fish moving “up stream”
Gambia
“Hydrology”/Stream Paths
• Fill Sinks
• Find direction
• Find Accumulation
• SetNull(“Accumulation”<Desired, ”Accumulation”)
• Stream Feature
• Make a network?
Fill Sinks
Direction
Flow Accumulation
Null Non-Stream Pixels
• SetNull("Accumulation"<10000,"Accumulation")
Stream To Feature
What happened here?
Goes “straight” through lakes
A stream network?
Puerto Rico Streams
Missed Connections
Be Careful with “Near”
Islands and Channels
Natural Earth: Oregon
Stream Ordering
Stream Order
Gauge & Tidal Stations
• Gauge Data: USGS– Flow at a point on a stream/river
• Tidal Stations: NOAA– Tide and/or current at a location
Hydrologic Unit Codes (HUCs)
http://water.usgs.gov/GIS/regions.html
Hydrologic Unit Codes
Sub-Catchments
Lakes
National Hydrography Dataset
• NHD
http://nhd.usgs.gov/
Next Steps?
• Create a stream network– Combine streams from multiple rasters– Compare the accumulated pixels to gauge
station measurements
• Create watershed– Point along the stream can be a “pour” point
• Create lakes?– Constant elevation above the “pour” point
• Get other software?
HEC-RAS
Hydrologic Flow