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, . l~j~l<S QOCJ\[A.. ~h V\ cuJ 6r~/k~.f\der Iq<6'tA..~~~a Me e Re Me e te ~o ~ lssourl lver ltlga Ion: -~&~~~ A System Approach ~0~ ~ ~" ~ ~~ tff t-.. v - .;:- ~ ~'~ .~~ 9..~ ~. ,,",,\ ... 0'"' . I ~ L rc,.~ ' r r~ \\ ....-k. i \ t;, ~/\~ , . I', . , ," \ ?~' Larry W. Hesse, Gerald R. Chaffin, and Jerry Brabander ABSTRACT Channelization of the Missouri River from Sioux City. Iowa. to the mouth at St. Louis directly e1iminatl!d 192.071 hectares (474.600 acres) of aquatic and terrestrial habitat from the activl! erosion zone; agricultural and urban encroachml!nt has affected an additional 728.460 hectares (1.8 million acres). The Water Resources and Development Act of 1986 authorized a mitigation package which would result in the acquisition of 12.100 hectares (29.900 acres) of habitat; this mitigation would replace only 6.3% of lost habitat. Development of this land should proceed in a manner consistent with the view that the river is an ecosystem. The system approach suggests that: (1) successful mitigation is related to the extent to which natural channel and floodplain morphology and vegetative cover are replaced; (2) mitigation must be an ongoing program which recognizes need beyond that which has been already identified; (3) a "Trust Fund" is an appropriate instrument to provide for the allocation of funds for recovery projects; and (4) system users should help to pay for fish and wildlife recovery plans. , 'The character of a stream is determined by the character and magnitude of the basin it drains and its climate" (Sedell and Richey 1989). Stream ecology is a relatively new science and even though research- ers, for the past decade or more. have recognized that streams function as integrated systems (Hynes 1975; Platts 1974). only recently have data been gathered from around the world to permit us to test the concepts concern- ing the important features of these systems. One of the most provocative stream concepts is that proposed by Vannote et al. (1980). Termed the river contin- uum concept. it perceives a river as a . . . continuously integrated series of physical adjustments and resource gra- dients along which the biota and eco- system processes in downstream reaches are linked to upstream reaches. Subsequent research and re- view of data from several rivers of varying size and basin conformation suggest that all rivers do not conform precisely to the central precepts of the original river continuum concept (Se- dell and Richey 1989). Clearly. how- ever, there are fea tures tha t do conform and as the science of stream ecology evolves, the relationship of individual river system components will be more readily understood. Stalnaker et at. (1989) stated that in the past floodplains were viewed pri- marily as a source of microhabitats, and modeling efforts often led to the erroneous conclusion that high flows (Le., floods) have a limiting effect on fish production. This conclusion was reached because past models did not account for microhabitats created within floodplains during flood events. Thus, analyses often overestimated the negative effects of increased depth and velocity in the main channel. Evidence today suggests that a flood not only makes floodplain habitat seasonally available to aquatic inhabitants. but is also important (1) for maintaining natural channel morphology, (2) as a mechanism whereby primary energy and nutrients are transported from up- land and floodplain sources to wetland and aquatic communities, (3) as a con- trolling factor in floodplain plant suc- cession, and (4) as a nutrient cycling mechanism that enhances productivity Larry Hesse is all aquatic rcscarch biologist witll the Nebraska Game and Parks Commission. P. O. Box 934. Norfolk. N E 68701. Most of his 15 Yf/lrs with the Commission have been Spellt studyinS the rclationship between biota and the altered physiCilI system that is the present day Missouri River. Gerald Chalfin is a water resources planner with the Nebraska Gall/e and Paries Commission and Jerry Brabander is the Nebraska state supervisor for fish and wildlife enhancement for ti,e Fish and Wildlife Service in Grand Island, Nebraska. January - February 1989 of floodplain vegetation (Bragg and Tatschll977; Bayley and Petrere 1989; Welcomme 1989). The objectives of this paper are to: (1) broadly define the extent of habitat loss in the Missouri River ecosystem; (2) define the role the Water Resources Development Act of 1986 can play in Missouri River mitigation; (3) define an ecosystem approach for the expendi- ture of Missouri River mitigation dol- lars; and (4) describe the precedent approach for mitigation and enhance- ment in the Columbia River ecosystem, a possible role model for the future of the Missouri River. Channelization of the Missouri River directly eliminated 40,591 hectares (100,300 acres) of aquatic habitat and 151,479 hectares (374,300 acres) of wet- land and terrestrial habitat from the natural river and its active erosion zone (U .5. Fish and Wildlife Service 1980) in the reach from Sioux City. Iowa, to the mouth at St. Louis, Missouri. Channelization, along with the flood protection provided by mainstem and tributary reservoirs, has fostered agricultural, urban, and industrial en- croachment on 95% (728,460 hectares) of the floodplain. This extensive de- velopment has dramatically changed the composition of the natural plant communities that formerly colonized the floodplain, reduced available sup- plies of organic material by at least 65% and interrupted vital life processes for nearly all of the native resident and migratory fauna that depended upon habitat along the Missouri River cor- 11