Research Trends and Results

Proposal for Enhancing River Environment
Management
FUKUHAMA Masaya, Research Coordinator for Water Environment, River Department
HATTORI Atsushi (D.Eng.), Head; NAKAMURA Keigo (D.Eng.), Senior Researcher; SUZUKI
Hiroyuki, Researcher; MAEDA Yoshiyuki (Dr. Agr.), Guest Research Engineer
River Division, River Department
Keywords: river environment, management, Ecological niche model

1. Maximizing the information on riverenvironment
In realizing the conservation and restoration of abeautiful and natural river environment, basic riverenvironment information is mainly obtained from thebiological surveys, called the National Census of theRiver Environment ("Census"), which is conducted every
5 years. A river environment information map iscreated by summarizing the Census data in a map. Suchinformation has become available this decade andaccordingly basic knowledge of the conditions of riverenvironments in Japan has been increased. Therefore,efforts should be made to utilize such information andknowledge in the practical river management, with theaim of enhancing the effectiveness of management.
2. Issuesinpracticing
environmental
management and solutions
Generally, management consists of four items:monitoring and evaluating conditions, improvement
measures, and target setting. As a result of applying thisto the management of a river environment, issues andsolutions in each item are considered as follows.
○ Issue 1 <Monitoring the conditions> Measuring thedistribution / amount of habitat
In river environment management, not only living
things but their habitats are generally taken intoconsideration. Particularly, for what regards river
channel topography and vegetation, a good balance offlood control conditions, such as discharge capacity, andenvironmental conditions, such as good habitats, isneeded, and is one of the targets in practical management.
For what regards physical habitats, neither amechanism nor a survey method for periodicallycollecting data has been established, as in the Census, e.g.,
distribution or amount (e.g. area) of rapids and pools
essential for fishes. For this reason, it is necessary toestablish a mechanism for obtaining habitat data
periodically.
○ Issue 2 <Evaluating of the conditions> Evaluating
habitat quality
The quality of a habitat is evaluated by checking theinhabitation of living things under the Census against thecondition of the habitat. Since the Census is conductedin typical areas, a method is required to evaluate thecondition of habitats in other areas.
○ Issue 3 <Improvement measures> Providing technicalinformation on improvements / management
For the river segments under the control of the national

government, technical information as to what approach isappropriate or should be avoided for eco-friendly river
improvement / management is lacking. It may require
steady efforts, but it is necessary to focus on collecting
existing data for the locations improved as part ofactivities in Issue 1, and provide the obtained
information.
○ Issue 4 <Target setting> Need further discussion
Many discussions have been made on setting targets
but not yet reached a conclusion. Therefore, practicalmeasures should be continued in order to maintain orimprove the present situation for the time being.
3. Development of habitat evaluation methods
The NILIM, in collaboration with the MLIT, Regional
Development Bureaus, and Public Works ResearchInstitute, has been studying the aforementioned issues
since last fiscal year. To represent our study, thefollowing describes Issue 2. For Issue 2, studies areunderway on the application of an approach (ecologicalniche model) for evaluating, based on habitat information,
the appropriateness of a habitat as probable habitat for acertain type of organism (indicator species). This issue
was studied using Census data on fishes and physicalenvironment data on 1 km sections plotted in 2006 for therivers under the direct control of the national government(Figure).
In the future, we will also study practical measures for
Issue 2, using this kind of models.
Upstream

Midstream (2)Midstream (1)Nephropidae habitat probability(present condition)

Check status (Nephropidae - 2005)○ Present Not present

Figure: Example of Habitat Potential
Evaluation with Ecological Niche Model