|
<br />,..,~
<br />; I I
<br />-,''^'-
<br />}II
<br />.; I
<br />,
<br />
<br />
<br />I
<br />
<br />766 JULY 1977 H~ WHITEWATER CHANNEL 767
<br />
<br />desirable to maintain this slab intact. The l.ength of the chute would be betwee~dePths great enough to require extensive eXFavation below the grade of the
<br />500 ft and 600 ft (152 m and 183 m), and the rIver bottom would be at approximalel'exisling river banks would be minimized to reduce construction costs.
<br />E!. 79.0 at the end .of the chute. ,The ~aximum width of the chute wouk WhitewaterCriteria.-For an interestingwhitewatercourse-on ethat is neither
<br />be 40 ft (12.2 m) with the east (rIver) Side of the chute conforming to too boring nor too challenging-the chute should be designed to provide Class
<br />III water as defined in Fig. 3. Associated with this class of water would be
<br />numerous eddies and waves on which a boater could "surf" (i.e., maintain
<br />his position in an upstream direction on the sloping face of a wave with minimal
<br />paddling). Through proper placement of these eddies and standing waves, boaters
<br />should be able to return from the downstream end of the chute to the upstream
<br />pool.
<br />Safe/y.-Because the channel would be part of a public recreational park,
<br />-swimmers, inner~tubers. rafters. and open canoeists. as well as whitewater
<br />boaters, should be able to negotiate the chute safely. In particular. the edtry
<br />into the chute and the exit into the river were locations of potentially dangerous
<br />bydraulic conditions.
<br />ObjectIves 01 Studies.-Because a numerical solution for developing a hydraulic
<br />ilructure complying with the stated criteria is not possible. a physical model
<br />,test program was undertaken. Specific objectives were to
<br />
<br />I. Determine the basic geometry of the channel (Le..length. width. alinement,
<br />,bottom slope, and location and shapes of obstructions and berms). Satisfactory
<br />= 0.028 m3 Is; 11 geometry would include conformance to the site conditions of a near-constant
<br />upstream reservoir elevation, a bike path and a spectator area between. the
<br />channel and the existing railroad on the west bank of the river. a smoothly
<br />curving alinement on the east side of the' channel, and retention of existing
<br />trees on the west river bank. From observing movies and reading the report
<br />of the Olympic course in Augsburg. Germany. it was determined that sloping
<br />walls would be desirable throughout the chute. The vertical channel walls at
<br />Augsburg were believed to promote undesirable reflected waves and to increase
<br />",rging.
<br />2. Develop the basic design of an entry gate and transition that would pass
<br />wiable flows while maintaining a constant upstream reservoir elevation. and
<br />. the same time permit safe transit of boaters from the reservoir into the
<br />channel.
<br />3; Determine the hydraulics of the channel, including how much head loss
<br />sliould be absorbed in the entry, in the chute itself, and at the exit. Determine
<br />the operating characteristics and control problems associated with all flow
<br />conditions, including misoperation of the entry gate and the fabridam. to maximize
<br />. sot. hydrauli~ conditions.
<br />4. Satisfy the criteria of Class III water. provide satisfactory positions for
<br />. banging gates for a slalom course. provide velocities no greater than IS fps
<br />14.6 m/ s), provide sufficient depth for Eskimo rolls, and determine proper
<br />placement and shaping of obstructions and berms to enable boaters to return
<br />upstream.
<br />5. Develop the obstacles and berms with simple geometrically similar shapes
<br />6.e.. uniform side slopes and radii of curvature) so construction formwork would
<br />oot be difficult, precasting may be possible, and forms for cast-in-place construc-
<br />tion would be reusable. Significant construction cost reductions can be realized
<br />. by meeting this objective.
<br />
<br />.-
<br />
<br />
<br />\
<br />\
<br />I
<br />
<br />CLAn :r.:IIl:
<br />
<br />.'-
<br />,
<br />
<br />ClASSl
<br />
<br />.
<br />.
<br />
<br />- -
<br />CM.....UIlOPi lfTlFtj
<br />
<br />FIG. 3.-Whitewater Classific:ation Versus Slope end Flow (1 cis
<br />It ~ 0.305 m)
<br />
<br />
<br />~. c'
<br />',,'. .
<br />'"', ..
<br />~"~- ',~;, -:'.,b",
<br />:"-~'~'/ ~
<br />
<br />FIG. 4--Fine' Model
<br />
<br />river channel, so as to present the least possible obstruction to river flow at
<br />high stages. The west side of the chute would be dictated by a path and spectallX
<br />area on the west bank, between the chute and an existing railroad track. A
<br />minimum depth of 2 ft-3 ft (0.6 01-0.9 m) of water was desired so that.
<br />kayaker or whitewater canoeist can successfully perform an Eskimo roll; however,
<br />
<br />.1
<br />
<br />"
<br />
<br />i
<br />
<br />1
<br />I
<br />,
<br />j
<br />!
<br />
<br />i.
<br />
<br />I
<br />
<br />~
<br />
<br />1:
<br />
<br />~,
<br />
<br />"
<br />!i
<br />
<br />i
<br />1,
<br />
<br />I:
<br />
<br />''''.''
<br />
<br />, , , "",,<., ,,~.-' ,: r _'J, '. i 'P "., lit
<br />
|