Evaluation of regional groundwater flow by dredging the Hida River, Gero district in Gifu Prefecture...
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Transcript of Evaluation of regional groundwater flow by dredging the Hida River, Gero district in Gifu Prefecture...
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
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
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
Basin summary of the Hida River
in the Gero district
Gero, Gifu
Hida River
Koden district
Shogano district
Ogawa district
Mori district
Area of the analysis
Yunoshima district
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)
Gero-ohashi bridge
Koden district
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
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)
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
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
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
Range of the analysis
Comparison after/before dredgingContour line of after dredging
Contour line of before dredging
Contour line, in the Koden district
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
Mori district
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)
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)
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
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
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.
END