Hydrology Flashcards
Explain national topographic systems (NTS)
topographic maps made by natural resources canada - there are 3 standard scales available
What are the 3 standard scales of the NTS indexes?
- 1:1,000,000 (083)
-1:250,000 (083H) - 1:50,000 (083H05 (SW Edmonton))
Explain hydrological modeling
modeling the flow of water across a surface using info about the sahpe of the earth’s surface
what are the 3 steps when delineating watersheds or defining stream networks
- hydrologic conditioning
- watershed delineation
- stream network and characteristics
One of the ways to derive hydrologic characteristics of a surface
Ability to determine the direction of flow from every cell in the raster - determined by the direction of the steepest descent
Explain sinks
a cell or set of spatially connected cells whose flow of direction cannot be assigned one of the eight valid values in a flow direction raster
Define depressionless DEM
DEM that has removed all sinks
What casues sinks?
caused by sampling effects and the rounding of elevations to integer numbers
what are 2 methods of removing sinks?
Fill: raises sink cells such that sink cells flow
Cut: lowers neighboring cells to level so that sink cells flow
What are two methods of stream order?
Shreve and strahler
Explain shreve
all exterior links are assigned an order of one - number of upstream links are referred to as magnitudes
Explain strahler
increases in order at intersections of the same order, but it does not account for all link and is sensitive to the addition or removal of links
how to compute the flow direction of a water shed
- user provides locations of catchment areas
- flow threshold: the pour points for the watershed will be the junctions of a stream network
