Parks and park engineering . ing line is employed. A good soundingline can be made of sash-cord with a colored string tied ateach foot-mark. Different colors are used to good advan-tage, the number of feet being thus readily sinker will be required to hold the lower end of the lineto the bottom. Alignment of the sounding rod or ropemay be had by means of rods on the shore or else by distance is obtained by stadia or else by alignmentrods on a line at right angles to the other. Brooks and Creeks. The flow of streams is determinedby use of a weir unless the flow is large
Parks and park engineering . ing line is employed. A good soundingline can be made of sash-cord with a colored string tied ateach foot-mark. Different colors are used to good advan-tage, the number of feet being thus readily sinker will be required to hold the lower end of the lineto the bottom. Alignment of the sounding rod or ropemay be had by means of rods on the shore or else by distance is obtained by stadia or else by alignmentrods on a line at right angles to the other. Brooks and Creeks. The flow of streams is determinedby use of a weir unless the flow is large. In the latter case,which is not common, a current meter or rod float must beemployed. Fig. 9 shows clearly the customary method ofmaking weir measurements. Depths over the crest are measured either by a car-penters square or a footrule. For measuring depthsthe hook-gauge is never necessary except when litigationis probable. Measurements of flow may be made twice aday, or oftener when the water is rising or falling Loaned by J. & W. Jolly. Hnlynkp, Mass. FIG. 0. -Gauging the Discharge of a Stream, 33 THE HYDROGRAPHICAL SURVEY 35 In determining the discharge of a stream by meansof a weir great importance should be attached to the matterof keeping the weir crest free from floating objects, whichby backing up the stream may invalidate the readingseven after the brush is removed. Weir frames are oftenwashed out by freshets. To prevent this the frame shouldbe firmly set in a trench excavated for the purpose withriprap on the down-stream side to prevent scour. Shouldthe weir be found leaky or should leaks be apprehended, alittle clay placed on the bed of the stream against theupper face will be found very satisfactory. Full hydrographical information is required by the land-scape architect in his preparation of plans for lakes andwater courses, and by the engineer in connection withexcavation and dredging operations and the design ofoutlet sewers. CHAPTER III DESIGNT
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