Talk:Strahler number

When rivers divide

What happens to the order when a stream divides into more than one channel? —Ian Spackman 02:58, 4 July 2007 (UTC)

That's not related to the tributary problem discussed here, but some distributaries (i.e., Wax Lake Delta) are similarly fractal. Awickert (talk) 03:39, 2 April 2009 (UTC)

It is discussed in river bifurcation. I just removed some material from that article that more properly belongs here. —David Eppstein (talk) 04:24, 2 April 2009 (UTC)

Rooted trees

Looks good, just one comment: It might help the reader (at least me) if the page explicitly mentioned that everything here is about rooted trees. (In particular, "paths of degree-one nodes" is a bit strange if you think free trees. This could be replaced with something slightly less ambiguous.) — Miym (talk) 07:47, 1 April 2009 (UTC)

Pathwidth

The Strahler number of a tree is almost the same thing as its pathwidth, right? Can this observation be sourced, adequately enough to include it in the article? —David Eppstein (talk) 17:29, 1 April 2009 (UTC)

Shreve index of stream order

A similar measure of "downstreamness" is the Shreve measure whereby a channel with no previous tributaries would be a first order stream, a channel with three tributaries upstream would be a third order stream. My A-level geography class used this as a crude method of showing how downstream we were and it proved quite effective. If I havent been clear enough (probably not it's hard to explain) have a look at this website which has a quick diagram of both the shreve and strahler measures http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=Stream%20Order Would it be worth making a new page for this and tagging it onto "see also" or should the shreve method be added to the bottom of this page Biqh (talk) 10:11, 19 January 2011 (UTC)

Horton vs. Strahler

Please correct me if I'm wrong, but from reading Horton's paper and Strahler's it seems that Strahler's criteria is exactly the same as Horton's. It's just that Strahler defined it much more clearly; but his claim that it's a modification of Horton's seems erroneous. If there is a difference, what is an example that would illustrate this? ToneDaBass (talk) 01:10, 21 October 2011 (UTC)

I don't know either. I think that's the reason that when I gave this a major revision in 2009, I left it vague about how much of the definition is due to Horton and how much to Strahler. Of course, if it is unfairly named in the literature, that's not for us to change. —David Eppstein (talk) 01:42, 21 October 2011 (UTC)

I think I've found the answer. In Shreve, R.L., (1966). Statistical law of stream numbers. The Journal of Geology, 17-37., Figure 1 (page 19) he shows Horton's Stream order scheme compared to Strahler's. The Horton one is taken from Horton's 1945 paper (page 297). This shows the subjectivity inherent in Horton's method, as opposed to Strahler's being much more objective. So in fact, there is a true difference between the two. —ToneDaBass (talk) 00:13, 22 October 2011 (UTC)

river networks

I propose splitting that section into a new page. It is a notable topic per se and the new article can talk about the implications (e.g. the relationship between bifurcation ratio and the chance of flooding) instead of focussing only on the maths. Kayau (talk · contribs) 01:23, 12 January 2013 (UTC)

river networks

I find this problematic:

 "To qualify as a stream a hydrological feature must be either recurring or perennial. Recurring (or "intermittent") streams have water in the channel for at least part of the year."

A dry creek bed or rivulet would therefore qualify as "recurring" (= "intermittent") if it barely trickled once a year for a few minutes. Plus, one would have to be present at the right instant to observe that flow. And surely, if one looked more closely (fractally so to speak) one would find signs of arbitrarily tinier nearly always dry rivulets, like micro-tributaries. So the notion of a first order stream seems to lie in the eyes of the beholder. Strahler's paper claims an objective criterion but suffers from a similar ambiguity:

 "Stream orders have been defined by Horton (1945, p. 281-283), but the writer has followed a somewhat different system of determining orders: The smallest, or "finger-tip", channels constitute the first-order segments. For the most part these carry wet-weather streams and are normally dry. A second-order segment is formed by the junction of any two first-order streams; a third-order seg- ment is formed by the joining of any two second- order streams, etc. This method avoids the neces-sity of subjective decisions, inherent in Horton's method, and assures that there will be only one stream bearing the highest order number." 

In a nutshell, "normally dry" is no more objective than "at least part of the year."

Also, the schematic of the "correct conversion of water bodies to a tree network" seems to impose a precedence on the 3 tributaries flowing into the lake, namely that the upper most tributary joins the lake "upstream," followed by the left tributary and then finally the right tributary. A correct and unbiased conversion would seem to show all 3 tributaries as peers converging at a single node. (Nevertheless the Strahler number resulting from both conversions is the same, namely 3.) Wiki egret (talk) 23:32, 7 October 2017 (UTC)

References

Edges or nodes?

The figure at the top shows Strahler orders assigned to edges, whereas the text describes assigning Strahler orders to nodes. Strahler's paper from 1957 (Transactions of the American Geophysical Union, pp. 913ff) describes the former (orders for edges). Please object if I'm mistaken, but I think the text should be adapted accordingly (and I could do so). — Preceding unsigned comment added by 80.226.24.15 (talk) 10:03, 6 October 2015 (UTC)

One gets the same collection of numbers either way. The number for an edge is the same as the number for the upstream endpoint of the edge. But in the other applications I think node numbering is more common. We should explain the equivalence between the two positions of the numbers, but it would be helpful to find a source for it. —David Eppstein (talk) 17:46, 6 October 2015 (UTC)