Post on 08-Aug-2020
Developing an evaluation method for channel widening
－Towards a friendly river to fish and people －
Group 7
Clean up campaign in Kakogawa River with Wakamiya Elementary School students 1
キーワード
Contents
Keyword Motive and purpose
Evaluation method and its accuracy
Conclusion
Acknowledgements References
Ecosystem Flood prevention
Sustainability of cross sectional shape
2
Keyword
River channel widening dredging a river to prevent flooding
Channel widening
ユールストローム図…
M.L.I.T plan
the plan carried out by the ministry of land, infrastructure, transport and tourism
3
Target area
downstream area of the Kakogawa River
First-class river
Kakogawa River basin
Target area
Hyogo Prefecture
Kakogawa city
Kakogawa River
4
Especially important for our lives and economy
National governments are tasked with the management for these rivers
・
・
Motive｜flooding Kato city Touryu Bridge
Target area
Hyogo Prefecture
Kakogawa city
Kakogawa River
Kato city
Channel widening is necessary
5
Motive
The number of fish decreased after channel widening
Habitat quality decreased
the number of the fish captured per one time of casting net
＜Hakuryo Junior&Senior High School Biology Club ＞
Red line: the year when conducted channel widening
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[year] Red line: channel widening
The
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er o
f fi
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Purpose
Existing evaluation
事前評価… 事後評価…生態系，持続性
Sustainability…lower the frequency of channel widening
Habitat suitability…estimate the effect on the ecosystem
Let’s evaluate beforehand!! ② Suggest a new widening plan
using new method
Merits of prior evaluation
Habitat suitability, Sustainability…after channel widening River flow…before channel widening
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Establishing a method to evaluate channel widening plans beforehand
Evaluation method
Calculating velocity and depth
Ecosystem diversity
Flood prevention
Sustainability of river channel
8
Calculating velocity and depth
Tool:iRIC
Velocity(m/s)
Velocity distribution map （4.2㎞～6.8㎞ from river mouth）
Target area 3.8㎞～11.8㎞ from river mouth
Discharge 27[m3/s]
Time 30,000[s]
Calculation conditions
Average velocity: 0.4[m/s]
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EED[Eco-Environmental Diversity] Index to evaluate the diversity of habitat EED has a positive correlation with the number of species of fish reference：Hirohumi ito ,Research on practical application of fish habitat evaluation
in small-scale rivers ,2016-4
流速と水深についてEEDを算出
depth(m)
velo
city
(m/s
) ～0.2 0.2～0.6 0.6～
～0.2 a1 a2 a3
0.2～0.6 a4 a5 a6
0.6～1 a7 a8 a9
EED = 1－ 𝑎𝑖2
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𝑖=1
a:the relative proportion of each environment
Ecosystem diversity｜Evaluation method 10
Flood prevention
Calculate water surface elevation during flood discharge
Compare with government-run widening plan
過去最大の増水にも耐えられる流量で 計画高水流量を流すことができれば 河川の氾濫の危険性は低いといえる
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Sustainability of river channel cross section
Hjulström diagram
Grain size：35.6mm
Deposition：
Under 0.55m/s
Erosion：
Over 2.3m/s
Grain size[mm]
Flo
w s
pee
d[c
m/s
]
Transport
Erosion
Deposition
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Calculation results
Accuracy of iRIC calculation
Actual measurement
結果
Actual measurement Calculation
4.2km 0.52m 0.67m
5.0km 2.12m 2.24m
compare
Difference：about 0.10m
The calculation is accurate
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Field work measure actual water surface elevation
1km 4.6km sedimentation 0.223 > 0.208
erosion 0 ＝ 0
Accuracy of evaluation of sustainability
The change of cross sectional shape
compare
結果
Light green：deposition Orange：erosion
1km (H27 to H29)
4.6km
(H24 to H29)
Deposition 1km＞4.6km
Erosion
1km≅4.6km
This evaluation method is accurate.
1m
25ｍ
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（reality）
Evaluation results
（simulation）
Velocity and depth
Calculate them using iRIC
Observe it after digging
Ecosystem preservation
Evaluate it using EED beforehand
Evaluate the effectiveness of flood prevention using iRIC
Evaluate it using Hjulström curve beforehand
Observe it after digging
Before
New method
Sustainability of cross sectional shape Flood prevention
Conclusion｜ Evaluation method
Before
New method
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:
:
:
:
Conclusion
・河道掘削において、断面を事前に、簡単に、 定量的に評価する方法を開発し、その有効性を示した
・開発した断面の評価方法で、掘削案の改善ができる ことを示した
Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins
Confirm the accuracy of the evaluation method
・
・
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Future issues
・Make a better channel widening plan
・Examine the accuracy of our evaluation method in greater detail
・Consider interactions among various kinds of fish
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Acknowledgements This study was supported by these people.
M.L.I.T Himeji Office of River and National Highways
Associate Professor, Department of Civil Engineering, Graduate School of Engineering, Osaka University
Mr. Masayasu Irie
Mizuho Information & Research Institute, Inc
Mr. Keisuke Inoue
Civil Engineering Research Institute for Cold Region
Mr. Toshiki Iwasaki
Hakuryo Junior&Senior High School Biology Club
We’d like to acknowledge their great help.
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References
・Evaluation and monitoring project commission．“Re-evaluation for the Kakogawa River improvement ”．Kinki Regional Development Bureau． 2011-12．https://www.kkr.mlit.go.jp/plan/ippan/zigyohyoka/ol9a8v000000dn20-att/4.pdf. （referred on 2018-09-17）
・ M.L.I.T Himeji Office of River and National Highways “an outline of the Kakogawa River basin”．2008-07-16．https://www.kkr.mlit.go.jp/himeji/iin/kako_ryuiki/pdf_files/20080716siryou7_vol01.pdf
（referred on 2018-09-17）
・Kakogawa River basin council，“The second Kakogawa River basin council, document 6（the report of the progress of the project）”.
・Hirohumi ito ,Research on practical application of fish habitat evaluation in small-scale rivers ,2016-4
（In Japanese）
・事業評価監視委員会．“加古川直轄河川改修事業再評価 近畿地方整備局． 2011-12．https://www.kkr.mlit.go.jp/plan/ippan/zigyohyoka/ol9a8v000000dn20-att/4.pdf．
（参照日 2018-09-17）
・国土交通省姫路河川国道事務所 “加古川流域の概要”．2008-07-16．https://www.kkr.mlit.go.jp/himeji/iin/kako_ryuiki/pdf_files/20080716siryou7_vol01.pdf
（参照日 2018-09-17）
・加古川流域懇談会，“第二回加古川流域懇談会資料6 事業の進捗状況について”
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Thank you for listening !
Discussion with M.L.I.T Himeji Office of River and National HIghways
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Q&A
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New channel widening plan
Blue：government’s plan • Flat • Hard to inhabit for various
species
Orange：cross-section A • Various water velocities
Light blue：cross section B More differences in depth than government’s plan
B A
Water surface
1m
25ｍ
Government’s
plan
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Evaluation results
Government’s plan
New plan A New plan B
Ecosystem diversity 0.793 0.837 0.822
Flood prevention criterion +0.06ｍ -0.06ｍ
Sustainability 42％ 34％ 37％
A B
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Example Applications of iRIC
・Inundation Simulation of Oda River in 2018 West Japan Flood ・Debris flow simulation in West Japan Flood Disaster
of 2018 in Kumano, Hiroshima, Japan ・Inundation Simulation of Shozu River
in 2017 Flood in Kyushu, japan ・A lot of research on rivers
Reference:iRIC Website＜http://i-ric.org/ja/＞
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27.1
19.3
11.2
11.1
8.4
7.3
4.9
3.8
2.3 1.0 3.4 Tanakia limbata
Freshwater minnow
Goby
Skin carp
Sugomoroko
Pike gudgeon
Dusky tripletooth goby
Sweet fish
Black bass
Blugill
Others
Proportion of the caught fish in about 5 km from the river mouth[%]
25 25
Sweet fish
50㎝ Skin carp
reference： WEB fish illustrated book
reference：M.L.I.T Himeji office of River and National Highways
Freshwater minnow
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The number of fish
[year]
the number of fish captured per one time of casting net ＜Hakuryo junior-senior high school biology club ＞
Lower stream Midstream
The number of fish
[year]
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Simpson’s Diversity Index
Cross sectional shape 29
The water level at flood discharge
Erosion at flood discharge
Government’s plan
１ ２ ３ ４
Erosion(％) 66 69 69 67 67
deposition（left）erosion（right）distribution map
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Satellite photo downstream of the Kakogawa River
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Cross-section 1m
25ｍ
River flow 400m
Water surface
Relationship between flow velocity, water depth, and water surface elevation
Bottom of the river channel
Water surface elevation
Water depth
elevation
Accurate
Accurate measurement by Himeji Office of River and National HIghways
Water surface elevation is accurate Water depth is accurate
Relationship between flow velocity, water depth, and water surface elevation
Water surface elevation is accurate Water depth is accurate
Area
Discharge[m3/s]=Area[m²]×Flow velocity[m/s]
Water depth is accurate Flow velocity is accurate
How to calculate flow velocity and water depth
Import the elevation data and make a grid
River bottom elevation
River flow
Target area 3.8㎞～11.8㎞ from river mouth
Discharge 27[m3/s]
Time 30,000[s]
… …
How to calculate flow velocity and water depth
Set calculation conditions
How to calculate flow velocity and water depth
Run the simulation
Calculation result of water depth
River flow
Widening of the width of a river
There is a house near the river, and width is not widened
Raising a dike
The top of the dike becomes the way, and construction is difficult
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Widening of the width of a river
Raising a dike
Dredging the bottom of a river, widening of the width of a river and raising a dike would affect the river ecosystem.
a river
Heavy rain falls, and a river rises.
The flooding is generated.
a river(conducted channel widening)
Heavy rain falls, and a river rises. But much water can discharge and are hard to occur a flooding.
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Geospatial Information Authority of Japan has already measured .
measure
measure
How to measure the water surface elevation
We can get the elevation here.
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20172016201520142013201220112010
sweet fish freshwater minnow skin carp [year]
the number of the fish captured per one time of casting net ＜Hakuryo Junior&Senior High School Biology Club ＞