Watershed Assessment

Question 1

How does a clear cut impact a basin?

Answer 1

More variability (More water flow during rainfall, faster evaporation).

Question 2

How do animals in a river impact a basin?

Answer 2

Nutrient load increases, bank erosion, bacteria can contaminate drinking water

Question 3

What are potential impacts to a watershed?

Answer 3

Changes to peak flows - increased surface run off, loss of water storage, snow melt rates
Landslides/mass wasting
Surface erosion - increased sediment load
Changes to riparian areas (channelized streams, loss of streams)

Question 4

When do most impacts happen?

Answer 4

Usually during significant weather events and extremes

Question 5

What is level 1 of watershed assessment?

Answer 5

Define the watershed
Define basin size (km, ha)
Designated a Point Of Interest
Measure sub-basins above POI (One stream order below main stream)

Question 6

What are face units?

Answer 6

Areas between basins that drain directly into the larger stream

Question 7

What are some measurements we make in watershed assessments?

Answer 7

Relative relief - difference in stream mouth and height of mountains surrounding the basin
Average gradient - indicates ability of stream to erode and transport it’s bed and sediments
Longitudinal stream profile (variance in stream gradiant)
Drainage density.

Question 8

Whatsoever of data needs to be collected for watershed assessment?

Answer 8

Peak flows in basins and subbasins
Logging
Range
Industrial developments
(many others)

Inventory of roads
Rating of erodable soils
Riparian buffers