In 1997, Ministry of Land, Infrastructure and Transport revised the River Act., and they newly add the aim of “the adjustment and preservation of the river environment” to those of “the flood control” and “the water use”. It is necessary to examine new methods for relating their opinions to the river improvement plan. Once the river policies promoted by the Old River Act improved inhabitant's living environment remarkably for a long time, and brought the expansion of the residential space widely. The river improvement projects contribute to the reduction of flood damage, when snow is melted in Hokkaido enormously. At the same time, the progress of the river improvement made association with the river estranged, and the improvement reduced the natural preservation ability. The new methodological purpose of the improvement and preservation of the river environment is included in the infrastructure that brings such affordability and comfort. The objective of this study is to adjust ideas of a river improvement plan, to propose the trial balloon and to examine a practical model to treat the concrete process of planning. The concrete decision process of a plan leads an approach to think about in terms of strategic environmental assessment (SEA). Here, the idea that makes the final agreement easily is proposed. Namely, the opinions and information can be exchanged with each other using three axes of planning process, that is, the administration process of decision-making, the participation process of community reflecting residents' opinions, and the adjusting process on such opinions and information. The workshop is available for constructing the interrelationship between administrative sector and inhabitants. We introduce some technical methods such as fuzzy structural modeling, conjoint analysis and fuzzy integral into the discussion in workshops. An example here is a river improvement plan in the middle stream of the Tokachi River. Through the planning systems, we conclude the following points: 1) The comprehensive planning system leaded the issues of the river improvement projects to be developed. 2) The contents and factors were founded due to discussions using Brain Storming, KJ method and FSM. 3) The alternative plans to be completed by using some components of river improvement were selected by Conjoint Analysis and those plans are assessed due to a kind of Multicriteria Analysis, namely, Fuzzy Integral (Choquet's integral). 4) Finally we can establish a stage where the complicated alternative plans are discussed and assessed. And then, we can also determine the appropriate plan smoothly in terms of such discussions.