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<br />5 <br /> <br />Stream Channl,ls <br /> <br />Ranking Stream Tributaries by Number <br /> <br />Historically, quantification of the Hnear segments of streat.s began <br />at the turn of the century with a European system that defined the! main <br />stem as first order (i.e., number one) all the way to its headwat..r origin <br />and then numbered tributaries so that unbrallched tributaries had the <br />highest order number. Later, a system was proposed that reversed the <br />sequence so that unbranched tributaries were given the, lowest ord..r number <br />(1.e., #1) (Horton 1932, 1945). Stresm order number f.dentif1es the <br />position of a stream segment in the hierarchy of triblJ,taries within a' <br />drainage basin. 'It is best described by a sketch of II hypotheticl,l <br />drainage network'(Figure 3). Strahler (1952) proposed a modification of <br />the Horton system whereby the main stem was ordered bi the same WlLY as the <br />other sections. According to the current I}" accepted 8.ystem of ordering, <br />the amallest unbranched tributaries of a strea. syatal are designated as a <br />number 1 or first order. Streall order is increased ltG' the next hf,gher <br />order whenever two streallS of the same order unite. p'or example, when two <br />first order strea.. unite, a second order stream is fc,rmed. The (Irdering <br />or ranking continues until each tributary in a drainage .ystem 11 numbered. <br /> <br />Second~ <br />order <br />. basin <br /> <br /> <br />11.ure 3. Stre.. order analysis. Note that the <br />the naII..r unbranched tl:'lbutarles are dest~n.llt.,d <br />as number 1 (First Order). Stream order 1s Incrt~ased <br />to the next higher order vhenevl!t' two streams of the <br />aalM order unite. The main atelll of the atre.. hi <br />alway. dealRnated by the highear. order number of the <br />drain.se .yar... <br /> <br />It takes at Iea.t <br />the next higher order. <br />cannot be increased by <br />a given order may have <br /> <br />two streams of sny g:lven order Ito form a stream of <br />A key point 'in the Ilystea is that stream order <br />the entry of a tribul:ary of a lc)wer order. That is, <br />more than two lower order segments: for ex.tmple, a <br />