Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method...
Transcript of Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method...
![Page 1: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/1.jpg)
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
![Page 2: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/2.jpg)
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
![Page 3: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/3.jpg)
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
![Page 4: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/4.jpg)
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
・
・
![Page 5: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/5.jpg)
Motive|flooding Kato city Touryu Bridge
Target area
Hyogo Prefecture
Kakogawa city
Kakogawa River
Kato city
Channel widening is necessary
5
![Page 6: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/6.jpg)
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
0
2
4
6
8
10
19
99
20
01
20
03
20
05
20
07
20
09
20
11
20
13
20
15
20
17
[year] Red line: channel widening
The
nu
mb
er o
f fi
sh
6
![Page 7: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/7.jpg)
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
7
Establishing a method to evaluate channel widening plans beforehand
![Page 8: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/8.jpg)
Evaluation method
Calculating velocity and depth
Ecosystem diversity
Flood prevention
Sustainability of river channel
8
![Page 9: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/9.jpg)
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]
9
![Page 10: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/10.jpg)
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
9
𝑖=1
a:the relative proportion of each environment
Ecosystem diversity|Evaluation method 10
![Page 11: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/11.jpg)
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
11
![Page 12: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/12.jpg)
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
12
![Page 13: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/13.jpg)
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
13
Field work measure actual water surface elevation
![Page 14: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/14.jpg)
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
14
(reality)
Evaluation results
(simulation)
![Page 15: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/15.jpg)
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
15
:
:
:
:
![Page 16: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/16.jpg)
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
・
・
16
![Page 17: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/17.jpg)
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
17
![Page 18: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/18.jpg)
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.
18
![Page 19: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/19.jpg)
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”
19
![Page 20: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/20.jpg)
Thank you for listening !
Discussion with M.L.I.T Himeji Office of River and National HIghways
20
![Page 21: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/21.jpg)
Q&A
21
![Page 22: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/22.jpg)
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
22
![Page 23: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/23.jpg)
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
23
![Page 24: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/24.jpg)
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/>
24
![Page 25: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/25.jpg)
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
![Page 26: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/26.jpg)
Sweet fish
50㎝ Skin carp
reference: WEB fish illustrated book
reference:M.L.I.T Himeji office of River and National Highways
Freshwater minnow
26
![Page 27: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/27.jpg)
0 2 4 6 8 10
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
0 2 4 6 8 10
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
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]
27
![Page 28: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/28.jpg)
28
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
19
94
19
95
19
96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
20
06
20
07
20
08
20
09
20
10
20
11
20
12
20
13
20
14
20
15
20
16
20
17
Simpson’s Diversity Index
![Page 29: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/29.jpg)
Cross sectional shape 29
The water level at flood discharge
![Page 30: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/30.jpg)
Erosion at flood discharge
Government’s plan
1 2 3 4
Erosion(%) 66 69 69 67 67
deposition(left)erosion(right)distribution map
30
![Page 31: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/31.jpg)
31
Satellite photo downstream of the Kakogawa River
![Page 32: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/32.jpg)
32
Cross-section 1m
25m
River flow 400m
Water surface
![Page 33: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/33.jpg)
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
![Page 34: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/34.jpg)
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
![Page 35: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/35.jpg)
How to calculate flow velocity and water depth
Import the elevation data and make a grid
River bottom elevation
River flow
![Page 36: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/36.jpg)
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
![Page 37: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/37.jpg)
How to calculate flow velocity and water depth
Run the simulation
Calculation result of water depth
River flow
![Page 38: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/38.jpg)
Widening of the width of a river
There is a house near the river, and width is not widened
![Page 39: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/39.jpg)
Raising a dike
The top of the dike becomes the way, and construction is difficult
![Page 40: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/40.jpg)
40
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.
![Page 41: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/41.jpg)
a river
Heavy rain falls, and a river rises.
The flooding is generated.
![Page 42: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/42.jpg)
a river(conducted channel widening)
Heavy rain falls, and a river rises. But much water can discharge and are hard to occur a flooding.
![Page 43: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/43.jpg)
43
Geospatial Information Authority of Japan has already measured .
measure
measure
How to measure the water surface elevation
We can get the elevation here.
![Page 44: Towards a friendly river to fish and peoplekakohigashi-hs/pdf/h30/kadai/...Development of a method to evaluate channel widening plans easily, quantitatively, and before widening begins](https://reader033.fdocument.pub/reader033/viewer/2022050514/5f9ea19fca690c07b73b5dc3/html5/thumbnails/44.jpg)
0
0.5
1
1.5
2
2.5
3
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 >