Messages from Departments and Centers of NILIM
Shed light on the river channel design!
FUJITA Koichi (PhD, Engineering)
Director of the River Department(Keyword) Foundation of study of technology policy, Disaster Prevention and Mitigation, Flood control, Rivers
technology, Climate Change Adaptation
1. Six Reasons to consider river channel design is very
important
It is a technology that integrates a plurality of objects.
For the creation of the river channel, maintenance,
conservation of nature, landscape formation, riverchannel use and easy flood control, completely
different nature of several important goals are required
for each purpose. Channel design is to aggregate atonly one point of how the shape of the river after all.
In this point, competence to proceed is asked thatthings are truly integrated.
It is a technology that does not escape abstract theory,
the theory of generalRiver channel design cannot be supported underdiscussion "debate should be like this" or "indicativeof the direction". In the end, we must decide on theform, so there is no room to replace the text
representation. Under the pressure that we must decideconcrete things, technical merits of the individual tobe charged will be apparent. Therefore, the techniqueand technicians engaged with the technology are welltrained.
Logic is required and people in charge will betrained
It is the technology of building social infrastructure isrequired logic in deciding. There is more than one
purpose, and the theory of integrating and adjustingthem is required to determine the shape. So, throughthe river channel design, logic of technology isexercised. The theory of negative effects of what it istrying to determine the things that have been
documented only in 100% logically is the logic thathas been trained proceeding to its destination and theturn will be coming for the first time. And to expose
the negative effects in the front of the theory andtechnology, then it is probably more likely to become
useless.
It will be a serious match called into questions of theresults

In consideration of various measures, it should befairly possible to develop the rivers relatively as soon
as possible. Aspect of river disaster recovery isdefinitely important. If this is performed, then theresult will appear in front as usual first appearance ofthe river, which is asked questions of the judgment ofthe quality; whether it is good to be true or not. Overthe years, a variety of further quality can be seen.
After 10 years to develop a river channel, thefollowing things become specifically apparent; to findwhat organisms, to give effective flood control in
response to the flood, and to fall within the expectedmaintenance effort. If there is a spirit that catches it,
river channel design is a unique opportunity for
hardball to improve technology.
To be thought of the basics of the river technology
The following inquiries of essential matters emerge:
if one wants to determine the shape of the river, how
the depth of the river? and how determined the widthof the river in the first place? : What do you think you
have to assume what the sediment supply? : How doesit come to its present form? : If we continue in thisstate, what does the form become? etc.. Directly, it
would be a discussion of the basic frame design ofriver channel. And it will lead to systematization of
the river and technology.
It is a technology that is open and connected toknowledge in various fields
Even saying to determine the shape of the bite,
utilization of knowledge is required in the following
various fields; Hydrology and Hydraulic Engineering,
Sediment hydraulics, of course, Geological terrain,
Geotechnical Engineering, and Biology, and such as
those involved in the ecosystem. And it is necessary tounderstand the relationship between the river andsocial and local conditions. The large number ofelements involved the diversity of those characters isdifficult to design river. However, those matters arealso a proof of being a technology that has beenconnected to the open state of the river which is also adesign community and the development of science andtechnology. You may also express it as "the junctionof rivers technology".
2. Now, four reasons to consider why the river channel
design is important
Standing position as a potential last resort of Disaster
Prevention and Mitigation
Increase due to the impact of climate change flood
flow has been an issue of concern. While a variety ofmeasures to address the larger flood will be examinedin one piece of hardware and software, we hit thespotlight inevitably also means that the excavation of
the river channel in order to increase the flow-throughcapability (flood discharge flowing through the riversafely). According to a simple calculation, Riverchannel tract area (Cross-sectional area of a riverchannel) increases by few %, probability of flooding
to occur outside the dike is reduced. For river channel
excavation, there is the difficulty to a certain degree.
However, it is a measure basically carried out only inriver. So depending on the degree to which thepractice of certainty would increase. In fact, many ofthe disaster recovery of the river channel excavation
are mainly focused. Therefore, without falling into theriver easy technique referred to as "you can simplydig"
by excavation carried out through theappropriate consideration, we need to keep the prideof a persons involved in the rivers technology.
It is a technology that makes the system, and make aterrain
River channel design can be expressed thetechnology to create a system that is responsible forthe formation or terrain. It is now commonly discussed
that it should assume that the external force isincreased in disaster prevention and mitigation by
occurrence of the phenomenon in the long term, once
hundreds of years or more. When we think of thedifficulty of ensuring the sustainability of such a timescale in social infrastructure to develop, we remind of
the importance of the workings of "creating a terrainthat may be present in very long-term" again. Today it
is also asked that putting in the river channel design
technical content that matches the true meaning of"making the terrain" of things.
Needs to go beyond the "River channel-oriented
Status"Technology system to advance properly to increase

cross-sectional area of a river channel was animportant place about the technology involved in theriver channel improvement by laying the basis of age
enhancement of flow-through capacity. On the otherhand, now we also aware that there is a change in theriver channel system of the formation and river
channel respectively based on the understanding that it
is important opinion arose. In other words, theimportance of river channel plan was grounded inso-called understanding of the characteristics of theriver channel. It was happened in the early Heisei
period. In this regard, "Emphasis river channel current
state" as a practical measure, in other words, the ideathat change unnecessarily low-flow channel that isformed over the years has emerged. And this has
become the starting point of river development even in
the current study. This is (the author is seen as) a
solution is a first-order approximation of river channel
development that you understand the characteristics ofthe river channel. But wouldn’t only emphasized"Status" or obsession have to walk alone? Would
understanding river channel characteristics and efforts
to river channel design that takes into account theunderstanding not have become blurred?
Now I
think we have been asked again river channel design
which is advanced to status-oriented.
The need for a large scale of time and space to think
Related to the fact above, we are much likely to focus
on each single event of interesting and important rightin front of you in the excavation of technology andresearch issues related to the river channel and thesetting process. Therefore, wouldn't the tendency toperceive how a dwarf compared to the scale of timeand space to think little about the technology thatmeets the river channel have come out? With theabove thing, bearing in mind the large changes in theentire river channel, and considering the nature of theriver channel is neglected, are we likely to prone tofall into the pattern from the next to the next toconsider the local symptomatic treatment? Or,
research interdisciplinary is seemingly progressing,
however, because of the above reason, it does not leadto the theory of technology to think the way the entire
river channel, putting into a new field which isvertically integrated namely comprehensive andintegrative. Consequently, would it become the ironic
situation? If more concern has become a reality in anyway, I think it is highly significant that the work fromthe front to the river channel design technology as akey to break it down.
3. The importance of making foundation for study ofhigh-quality technology policy
Everyone says that leading to practical measures tointegrate a variety of research and field information isrequired. If so, I want to emphasize that it is important
to try and establish a concrete way one by one in orderto decide how it should proceed. Comprehensive
approach is an approach to achieve things, therefore, Iwould also confirm that it does not itself become atarget. We should not be misled by the catchphrasethat looks attractive. And we create a foundation andwork together as forming the axial and specifictechnical issues and the goal which are surely
important. You may think challenges for "channeldesign" sounds a bit old school. However from thispoint of view, don’t you think it is not very importantand modern field? I intend to take better care of highquality foundation of study of technology policy.
Channel design is a representative, which is only oneof them.