70 ILCS 615/2
Such corporate authorities may lay out, construct and maintain a cut-off drain or ditch for the diversion of the flood waters of the Des Plaines river into Lake Michigan at some point north of the City of Chicago, for the relief and in aid of the drainage system established or to be established within said district, the location and route, dimensions and capacity of such cut-off to be determined by said corporate authorities. If the location of such cut-off shall occupy a portion of the North Branch of the Chicago river, said North Branch may be widened and deepened as shall be required. Such cut-off or diversion may be so constructed and maintained as to answer the purpose of a drain for the lands through which it shall pass, and such corporate authorities may allow said lands to be drained into the same upon such terms and conditions as they may determine: Provided, such corporate authorities shall not be allowed to interfere with any right of drainage which the owners of land have or would have, if such cut-off had not been made.
70 ILCS 615/2