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<br />70(1
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<br />HYDRAULIC ENGINEERING '94
<br />
<br />The results of the photogrammetric investigations showed that the deler-
<br />mina.ion of the surface of the water meets. the hydrological demands, especially if
<br />the relative change of the water surface level is of interest. The precision of the
<br />measurements of the bank lines depends on the interpretation and definition of the
<br />water boundaries Sometimes it was bard to define the boundary between water and
<br />lIIui1>lCned Mones. Furthermore. these difficulties were increased at covered and
<br />underexpost:d places of the model area. In future projects, the coloring of the waler
<br />or .he use of infrared films could facilitate the measurements of the bank lines in the
<br />stereo pairs.
<br />
<br />3.3. Sail-dilution method
<br />The sall-dilulion melhod is the best applicahle hydromelric melhod to deter-
<br />mine the discharge and the mean velocity of IUrbulenl uniform now in mountain
<br />rivers. h is based on lhe injeclion of a precisely known sale solulion quantity, and on
<br />the registration of the conductivilY graph.
<br />The most importanl parameter of solute transpon. the dispersion coefficient, is
<br />obtained through this method. This parameter is of increasing importance fur
<br />pollulion control and risk management.
<br />
<br />4. Results
<br />The resuhs of Ihe derived kst-coefficienls for two torrenl reaches in
<br />Switzerland are summarized in Table 2.
<br />
<br />reach olSCnarge lDean velocity kSI-coel!lcient
<br /> Iml/sl (mlsl Imlll/sl
<br />I .lZ-II.5~ 11.:14 - II.J~ 5 -
<br />2 .21-11.22 O.~' - 0.5ti 9 - 1
<br />2 '.34 - 0.39 O.U/-II.Uti IV - 1
<br />
<br />Table 2: kSl-coefficienls of210rrenl reaches hy lhe new approach (Hodel. /993).
<br />
<br />S. Conclusions
<br />Although lhe amounl of observations is small, the praclicality of this procedure
<br />has been proved. The observations, perfomled within a small range of discharge
<br />values lead to lower Slrickler coefficients than the commonly assumed values for
<br />torrents. '
<br />The following are recommended ror fulure use of this approach:
<br />Color film, or even beuer infrared film lo beller discriminate water against
<br />river bed. and resolution of at least ASA400.
<br />photographs should be taken as close to vertical as possible
<br />in order to gel ohservations over a wide range of disdmrge values, dilution
<br />method and photographs should be performed autumatically loll distinct rales IIf
<br />now IGru,ww, 1986)
<br />
<br />6. A I'Illication or Ihe proposed approach
<br />Improving and completing this approach through consecutive use at several sitc~
<br />could result in a new type of gauge. This gauge would provide nol onfy hydrographs
<br />accompanied by a rating curve of a very confined range of calibration values, hul
<br />also
<br />Strickler's kSI or Manning's n for a wider mnge of discharge values
<br />idealized mean cross-seelions of differeDltypes of lorrents and rivers
<br />dispersion coefficients
<br />
<br />~
<br />
<br />.
<br />
<br />EXTREME ROUGHNESS ESTIMATE-NEW
<br />
<br />701
<br />
<br />These chaf'dC~erislics may be useful for
<br />- COl.I~fXU"lson of channel capacily and excessive flood
<br />poss,ble effec.s of regulation - d' ""
<br />~xaminalion of hYdrological ~;pon t~~~.S,1r(~clIOCn:R(~~ l~e ,op~sile: revitalisalion)
<br />m carchmenl area SIS I.e. - constanl) aJong streams
<br />dclcrmining travel time of pollution slushes caused by accident or disaster
<br />7. Future research
<br />Future research direc'ion~ should be inOu d b he
<br />Could analog photographs'~ replaced b e;c~ I y t following questions:
<br />Which .racer can be mo ' ffi . Y Iglla Images?
<br />Is lhe length of a represe~t~ti~~C::~hr automat~ln than salt (conductivily)?
<br />Elemenlary Volume (REV) in ground~~:fh~dr~ut~c~; Represemalive
<br />
<br />The mosl import.ant goal lhough is 10 .. . .
<br />endargering lhe observation staff during pe~~~~;I~:W~:cedure IR order 10 avoid
<br />
<br />Appendix A. References
<br />
<br />Grunow, H. G., J986: Die auWmalische M . F . .
<br />Un/immung i 01' FUessgesc:hwimli keften e.~sung "on.. lIeSSUtlen utlll die
<br />Phof(}gr(munelrie, KuJturlech"ik. 12/86g 64/6;5 Bergbachen. Vermen"JJg,
<br />lIodel, Hp., Slorchenegger, I.: 1994' P~. Ne~ Po'" 1
<br />Torrent.\'. Proc..'eeditlgs of the /994 A"SeE N. mu u for Mean Veloc.'lty in
<br />1~'ngi1U!erinJl. Sessions l>>I Hyd l"'1' M, ~/w~1l1 Conjerem'c on Hydraulic:
<br />Hodel, Hp., Kersten TlL ~lIU Ie.! 0 flun!"", R,,,ers, Buffalo, New York, USA.
<br />Wilt/biiche" milteis Hy:"~ne,;~, 199J. SchlJtzung der Abjlussheih'erle vo"
<br />Phmogrammetric, KulturtecJmikm~:,IJe un~o IjPZhologrammelrie. Vermes.sung,
<br />HdlH .'7.pp.O".
<br />. 0 e, p,~ 1993: lJn/erxuchung lur Geomor hi'
<br />.')/romutiJ.:,\widerSlalldes und des Fliessvorpun~ . ~ 0 r:.~:'eh' der. Rauheit, des
<br />ETll.Ziirkh, Nr. 9830. Q Qes m erguuc en. D,ssertatio,,"der
<br />Slorchellegger, I"t 1984: Oru. und eli' . 'h h .
<br />.!(('h1ug-Ahj1u..'ls.Modelle. Diss~rtalion d~~E:;;'~ ~~~he~de 7~7rume/er fur Nieder.
<br />Slurchenegger, I., J 988.- Nalul7Ulhe B h rac;, r. 9,
<br />tltUiirJi(.'hen Fliessgewdssem In'erna~~ ge:tu/~"g uU/$rund von Messungen lUl
<br />Gru4 Band 4, pp. 397-407.' IOnD t!s ympos,um Imerpraevenl /988,
<br />
<br />Appendix B. Notation
<br />
<br />The following symbols are used in Ibis paper:
<br />
<br />A
<br />As
<br />('
<br />kSI
<br />I
<br />
<br />n
<br />p
<br />Q
<br />R
<br />v
<br />
<br />cross-sccJjUIJ area of How
<br />water surface area
<br />Chezy cocCt1cit:1lI
<br />Strickler's veJocity coefficient
<br />, reach length
<br />Manning's roughness factor
<br />welled perimeter
<br />discharge
<br />hydraulic radius .:e ratio AlP
<br />mean velocity
<br />
<br />-
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