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CLEVELAND APRIL, 1913 NEW YORK No. 4 Improving the Des Moines Rapids A Description of the Keokuk Dam Across the M ississippi River With Its Effects on Navigation HE: Mississippi river as far as obstructions other than low wa- ter-=are concerned is singularly avigation difficulties all the way fromeSt. Paul to New Orleans. In' fact there: are only. two places in this entire stretch requiring locks; one is at Rock Island and the other at the Des Moines rapids, near Keo- 'miles that its details are of concern to anyone interested in navigation on the Mississippi. river. The rapids at Keokuk were pro- duced by glacial action. The channel of. the -rrver:-at: this. point "ts: of -com- paratively recent origin and was orig- inally located some distance to the. west. The old channel: at some* pre- south of St. Paul.. This allows a dam at Keokuk with a comparatively small area overflowed by the pool above, thus keeping the cost of flood dam- age within reasonable limits and makes the proposition financially feasible. : The Des Moines rapids extend for a distance of about 12 miles from: FIG. 1--_KEOKUK POWER HOUSE AND DAM WITH LOCK SITE kuk. At Rock Island the lift require- ment is approximately 12 ft., and at Keokuk about 22 ft. At the latter point the Mississippi River Power Co. is now constructing an immense dam across the river primarily for the pur- pose of generating hydro-electric power. The work, however, incident- ally includes the construction of a large lock and dry dock and 'so alters the character of the stream for many historic time was dammed by the in- trusion of a glacier and the river forced to the. eastward. The condi- tions which caused the river to cut a valley 5 to 10 miles wide in the pre-glacial age were absent. in the post-glacial age when the _ present channel constituting the Des Moines rapids was formed. Asa result the bluffs and rapids are closer to the _ present river than at any other point IN FOREGROUND Keokuk to Montrose, Ia.; between these points the river bed has a fall of: 23. ft. The surface fall is about '16 ft. at high water and 23 ft. at low water, the greater part of this fall being. in. the lower 8 miles. The river is in a solid limestone forma- tion and its bed is practically smooth so that there are no broken water or surface disturbances during ordinary stages. The stream is nearly a mile