A STUDY OF THE EFFECTS OF STREAM CHANNELIZATION AND BANK STABILIZATION ON WARMWATER SPORT FISH IN IOWA: SUBPROJECT NO. 3. SOME EFFECTS OF SHORT-REACH CHANNELIZATION ON FISHES AND FISH FOOD ORGANISMS IN CENTRAL IOWA WARM WATER STREAMS

Six central Iowa streams were studied in 1974 to determine whether fish and fish food organisms were affected by short-reach channelization associated with bridge replacement in the last 15 years. In all cases the streams had been previously modified in the original bridge construction. The recent construction involved loss of 151 to 429 m of stream length in three streams and in the other streams the new channel was the same length as before. This would involve a loss of up to 18% of the stream if a bridge were built on each section line. Downstream the channel was narrower and shallower and perhaps had less brush shelter than upstream from the channel. Brush shelter was lacking in 2 of the 3 streams channelized in the last 2 years but had recovered somewhat, but not completely, in those channelized 10-15 years earlier. There was no evidence that dissolved oxygen, turbidity, or stream macroinvertebrates as measured by core, drift or artificial substrate samples differed upstream, in the channel, or below. The most evident impact of short-reach channelization is the removal of cover in the altered area and the loss of stream length.