physical modelling of the removal of glines canyon dam & lake mills by chris bromley, gordon...
TRANSCRIPT
Physical modelling of the removal of Glines Canyon
Dam & Lake Mills
By
Chris Bromley, Gordon Grant, Colin Thorne
University of Nottingham / Oregon State University
Source: National Park Service
Elwha River Project
“…the full restoration of the Elwha River ecosystem and the native anadromous fisheries…’
Elwha River Ecosystem and Fisheries Restoration Act, 1992 (P.L. 102-495)
Lake Aldwell ~ 2.98 million m3
Lake Mills ~ 11.85 million m3
Image courtesy of National Park Service
Baselevel
2.29 m =
2.8 cm
Research hypotheses The greater the magnitude of the drop in
baselevel,
a. The greater the incision and lateral adjustment that will occur within the original delta area
b. The more rapidly sediment will erode from the delta surface
c. The greater the total volume of original delta sediment will be eroded
Dam
Horizontal scale = 1 : 310
Vertical scale = 1 : 81.7
Vertical distortion = 3.79
3.3 km = 10.65 m
1.067 km = 3.44 m
45.72 m = 0.56 m
•Similitude of Froude No. & Shields No.
•Assume uniform steady flow
Qm = Qp * HV1.5
Qm growth = 110 l/min → Qp = 420 m3/s (14,825 cfs)
Amount of original delta eroded by different channel positions under the single and triple
notch scenarios
0
10
20
30
40
50
60
70
80
0 2,000 4,000 6,000 8,000 10,000Run time (minutes)
Per
cen
tag
e er
od
ed
1x L
3x L
3x C
3x R
Amount of original delta eroded by increasing incrementsof removal starting
from the central channel position
0
10
20
30
40
50
60
70
80
0 1,000 2,000 3,000 4,000 5,000
Run time (minutes)
Perc
en
tag
e e
rod
ed
3x C
6x C
12x C
21x C
Erosion rates of the original delta for the single and triple notch scenarios in
different channel positions
0
50
100
150
200
250
300
350
400
450
500
0 2,000 4,000 6,000 8,000 10,000
Run time (minutes)
Ero
sio
n r
ate
(cm
3/m
in) 1x L
3x L
3x C
3x R
Erosion rates of the original delta for increasing increments of dam
removal in the central channel position
0
100
200
300
400
500
600
700
800
0 2,000 4,000 6,000
Run time (minutes)
Ero
sio
n r
ate
(c
m3/m
in)
3x C6x C12x C21x C
R113x - center
R73x - left
0 - 21 0 - 21
R113x - center
R73x - left
3 - 21 3 - 21
R113x - center
R73x - left
6 - 21 6 - 21
R113x - center
R73x - left
9 - 21 9 - 21
R113x - center
R73x - left
12 - 21 12 - 21
R113x - center
R73x - left
15 - 21 15 - 21
R113x - center
R73x - left
18 - 21 18 - 21
R113x - center
R73x - left
21 - 21 21 - 21
Total dimensionless incision along initial delta topset
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
100 200 250Distance downstream along delta topset (cm)
Dim
ensio
nles
s inc
ision
(T
otal
inci
sion
/ in
itial
sed
imen
t dep
th)
1x Left 3x Left 3x Centre 6x Centre 12x C 21x C
Thalweg lengths for the different removal scenarios
200
400
600
800
1,000
1,200
1,400
0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000
Run time (Minutes)
Th
alw
eg le
ng
th (
cm)
1x L 3x L 3x C 6x C
12x C 3x R 21x C
Run From
(mins.)
To
(mins.)
Prototype
Sediment-transporting
time
(Weeks)
% total sediment volume
passing
Downstream
Yrs-worth of
Sediment
Transport
1x Left
7345 7765 7.0 8.41 6.6
3x Left
3430 3730 5 14.57 11.5
3x
Centre
3470 4360 14.8 32.69 25.8
3x
Right
2790 2940 2.5 3.72 2.9
Run From
(mins.)
To
(mins.)
Prototype
Sediment-transporting
time
(Weeks)
% total sediment volume
passing
downstream
Yrs-worth of
Sediment
transport
1x Left
7345 7975 10.5 13.54 10.7
3x Left
3430 4035 10.1 26 20.5
3x
Centre
3470 4720 20.8 40.08 31.7
3x
Right
2790 3430 10.7 15.54 12.3
Conclusions 1
• Volumes and rates of original delta erosion increase with,
-central incisional channels
-increasing magnitudes of removal
Conclusions 2• Beyond 3x C, relationships less clear,
-peak rates and volumes very high
during very early stages of removal
-increasing channel lengths d/s of original delta may represent negative feedback between original delta erosion and delta progradation
Acknowledgements • St. Anthony Falls Laboratory & NCED• Dianna Smith, Jason Lundheim, Mike
Plante, Dick Christopher, Ben Erickson, Jeremy Schultz, Josh Brand, Matt Leuker
• Brett Otteson, Ben Freisen, Corey Markfort• Alessandro Cantelli, Gary Parker, Chris
Paola, Greg Stewart, Tim Randle, Gordon Grant, Colin Thorne
• Brian Winter, Bill Jackson, Reclamation