stream.order {streamDAG}

Strahler or Shreve stream order of a stream DAG

Description

The function stream.order calculates Strahler or Shreve number for each each in a stream DAG. The function sink.G is a utility algorithm that subsets the graph if the sink node is part of a sub-graph that is disconnected from other nodes.

Usage

sink.G(G, sink = NULL)

stream.order(G, sink = NULL, method = "strahler")

Arguments

G

Graph object of class "igraph", see: See graph_from_literal.

sink

Sink node from G.

method

One of "strahler" or "shreve".

Details

Strahler stream order (Strahler 1957) is a "top down" system in which first order stream sections occur at the outermost tributaries. A stream section resulting from the merging of tributaries of the same order will have a Strahler number one unit greater than the order of those tributaries. A stream section resulting from the merging of tributaries of different order will have the Strahler stream order of the tributary with the larger Strahler number. Under Shreve stream order, (Shreve 1966) a stream section resulting from the merging of tributaries will have an order that is the sum of the order of those tributaries.

The function can currently only handle graphs with confluences (which, as noted above, serve to define the stream order) and simple islands (those without sub-islands and those whose downstream endpoint does not occur at a join). Under the current version, islands will not change the order of a reach.

Value

Returns Stahler or Shreve numbers for each stream DAG node.

Note

May be slow for extremely large and complex streams due to a reliance on loops.

Author(s)

Ken Aho

References

Shreve, R. L. (1966). Statistical law of stream numbers. The Journal of Geology, 74(1), 17-37.

Strahler, A. N. (1952). Hypsometric (area-altitude) analysis of erosional topology. Geological Society of America Bulletin, 63 (11): 1117-1142

Examples

stream.order(G = streamDAGs("konza_full"), sink = "SFM01_1", method = "strahler")

stream.order(G = streamDAGs("konza_full"), sink = "SFM01_1", method = "shreve")