![Page 1: Evaluation of regional groundwater flow by dredging the Hida River, Gero district in Gifu Prefecture Shoya KITAGAWA Course of Architecture and Civil Engineering](https://reader037.vdocuments.mx/reader037/viewer/2022110207/56649d1c5503460f949f1a58/html5/thumbnails/1.jpg)
Evaluation of regional groundwater flow by dredging the Hida River,
Gero district in Gifu Prefecture
Shoya KITAGAWA
Course of Architecture and Civil Engineering Gifu National College of Technology
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Background of the study
River channel dredging
The Hida River cannot secure Design Height Water Discharge
Drawdown of the groundwater level was forecasted
GROUNDWATER FLOW ANALYSIS
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Table of contentsIntroduction of the study domain
Method of analysis and analysis result
Analysis example of the Koden district
・ Background of the study・ Summary of the Gero district ・ Area division of the Gero district
Analysis example of the Mori district
・ Effect assessment of the dredging
Summary
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Basin summary of the Hida River
in the Gero district
Gero, Gifu
Hida River
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Koden district
Shogano district
Ogawa district
Mori district
Area of the analysis
Yunoshima district
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①considering several set of coefficient of permeability affecting the field survey②considering an incline of the impermeable ground
Method of analysisQuasi-three dimensional analysis
Basic equation of the groundwater flow
0,,
ry
zhhyxk
yx
zhhyxk
x
h: groundwater level measured on x-y plane (m)z: height of the impermeable ground(m)k: coefficient of permeability(m/s)r: water supply strength from the upper part(m/s)
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Gero-ohashi bridge
Koden district
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0352.0
353.0
354.0
355.0
356.0
357.0
358.0
359.0
360.0
0 2 4 6 8 10 12 14
Gro
un
d h
eigh
t(m
)
X direction
353.0 -354.0 354.0 -355.0 355.0 -356.0
Analysis condition (Koden district)
Range of the analysis
Boundary water level①Incline of the
impermeable ground
Neighborhood of the Hida River : k=14.4×10-5(m/s)Flat plains : k=7.73×10-5(m/s)
②The distribution situation of the coefficient of permeability
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0
4
356
357
358
359
360
361
362
363
364
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Gro
un
dw
ater
leve
l h(m
)
X direction
356 -357 357 -358 358 -359 359 -360
Range of the analysis
The point that groundwater level is high
The point that groundwater level is low
From this direction
Distribution of the groundwater levelbefore dredging(Koden district)
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0
4
356
357
358
359
360
361
362
363
364
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Gro
un
dw
ater
leve
l h(m
)
X direction
356 -357 357 -358 358 -359 359 -360
The Hida River
Distribution of contour line and current speed vector(Koden district)
Range of the analysis
Infiltration from the river to the bank inland
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0
4
356
357
358
359
360
361
362
363
364
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Gro
un
dw
ater
leve
l h(m
)
X direction
356 -357 357 -358 358 -359 359 -360
Contour line(Gero district)
Gero bridge
Upper stream
Down stream
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320
240
160
80
00 240 480 720 960 1200
X direction(m)-1.50 --1.00 -1.00 --0.50 -0.50 -0.00
1.0~1.5m
0.5~1.0m
Dis
tan
ce f
rom
the
rive
r(m
)
Range of the analysis
Distribution of the groundwater level drawdown when river water level
decreased 1.5m
About 240m
The Hida River
Influence of the dredging
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Range of the analysis
Comparison after/before dredgingContour line of after dredging
Contour line of before dredging
Contour line, in the Koden district
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Range of the analysis
Contour line, in the Koden district
Blue : After dredgingBlack : Before dredging
Contour line after and before dredging
Comparison after/before dredging
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Mori district
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0
3
6
9
345
350
355
360
365
370
375
0 2 4 68
10
Y direction
Gro
un
d h
eigh
t(m
)
X direction
370 -375
365 -370
360 -365
355 -360
350 -355
Analysis condition (Mori district)
Range of the analysis
Boundarywater level
②The distribution situation of the coefficient of permeability
① Incline of the impermeable ground
Mountain area : k=3.56×10-4(m/s)Flat plains : k=17.8×10-4(m/s)
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0
3
6
9
345
350
355
360
365
370
375
0 1 2 3 4 5 6 7 8 9 10 11
Y direction
Gro
un
dw
ater
leve
l h(m
)
X direction
355 -360 360 -365 365 -370 370 -375
Range of the analysis
Groundwater level
Distribution of the groundwater levelbefore dredging(Mori district)
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720
640
560
480
400
320
240
160
80
00 80 160 240 320 400 480 560 640 720 800 880
Dis
tan
ce fr
om th
e ri
ver(
m)
X direction(m)
-1.50--1.00 -1.00--0.50 -0.50-0.00
1.0~1.5m
0.5~1.0m
0~0.5m
Upper stream
Down stream
About 300m
Distribution of the groundwater level drawdown when river water level
decreased 1.5m
Influence of the dredging
Range of the analysis
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320
240
160
80
00 240 480 720 960 1200
X direction(m)-1.50 --1.00 -1.00 --0.50 -0.50 -0.00
1.0~1.5m
0.5~1.0m
Dis
tan
ce f
rom
th
e ri
ver
(m)
720
640
560
480
400
320
240
160
80
00 80 160 240 320 400 480 560 640 720 800 880
Dis
tan
ce fr
om th
e ri
ver(
m)
X direction(m)
-1.50--1.00 -1.00--0.50 -0.50-0.00
1.0~1.5m
0.5~1.0m
0~0.5m
Comparison of influence of dredging
Kod
en d
istr
ict
Mor
i dis
tric
t
About 240m
About 300m
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Summary
Groundwater of the Koden district
On the influence by dredging
・ Infiltration from the river to the bank inland is thought about near the Gero-ohashi bridge down stream.
・ The shape of groundwater flow does not change after dredging.・ Mori district is influenced considerably by dredging compared with Koden district.
Groundwater of the Mori district
・ Groundwater flow is not complicated compared with Koden district.
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END