1122251-0035
E-mail: workishikawa0612@yahoo.co.jp (Corresponding Author)( )2-4-15170-0004
E-mail: kawachi-a@tokencon.co.jp

1-15-6

1/5
1100 m3/s

1800 m3/s
10cm

Key Words: nature restoration, gravel riverbed, dam operation rule, stochastic analysis, numerical flowanalysis

1.

1)
1)
2), 3)
9)

4)
2)

3)
4), 5)

6), 7), 8)

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2.
(1)
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890 km2

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20 km

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6)1800 m3/s

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2003

m3

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1.5 2.0 kmm3/s

160 m3/s

11)

1947
2200 m3/s

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27
3

400 m /s

2 4m

1965
(2)
1/507)-3

940 m3/s

4)

1965

2017

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2011

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3

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8)1975 m3/s

395

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JR507)

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201112)

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n0.0022hI

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3 km

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4 6 km
-6

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-4
1800 m3/s(3)-61800 m3/s=//(4)

51

0.81800 m3/s

-9-9 (a)-5-61800 m3/s
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()

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()

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4.
0.05
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(1)
13)

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1100 m3/s

-92

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55-4-10 (a)Manning-10 (b)

1976
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5

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14)

10 cm15)16)-9 (b)(2)

1/100
1800 m3/s-3 (b)REFERENCES
1)-9 (b)

45
pp. 1105-1110 2001 [Tsujimoto, T., Murakami, Y.
and Yasui, T.: Growth of vegetation in fluvial-fan segment
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Vol. 85 No. 3 pp. 214-221
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2)

3)Vol. 44 No. 3 pp. 489-493
2019 [Gomi, T. and Ohira, M.: Gravel riverbed as an interface for ecosystem networks: spatio-temporal scale organization of watersheds, Journal of the Japanese Societyof Revegetation Technology, Vol. 44, No. 3, pp. 489-493,
2019.]

NOTES
1)
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9Vol. 40 No. 3
pp. 465-471 2015 [Sakio, H.: Why did the black locust
expand broadly at the river basin in Japan, Journal of theJapanese Society of Revegetation Technology, Vol. 40, No.
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2)()30123)
6135)

4)
159Vol. 57

No. 2

pp. 14-192015[Kayaba,Y., Taya, Y., Makishima, M., Akamatsu F. Nakanishi, T.
and Miwa, J.: Controlling method of regeneration of riparian trees for effective riparian trees management, Civil Engineering Journal, Public Works Research Institute, Vol.
57, No. 2, pp. 14-19, 2015.]

11)
45
pp. 619-624 2001 [Kadota, A., Suzuki, K. and Mori,K.: Study on flow resistance over steep-slope gravel-bed,
Annual Journal of Hydraulic Engineering, JSCE, Vol. 45,pp. 619-624, 2001.]

6)
12)

B1
Vol. 71 No. 4 pp.
I_631-I_636 2015 [Kometani, S., Michioku, K., Kanda,K., Irie, Y. and Sakumoto, C.: Equivalent Mannings’sroughness coefficient of vegetated alternative bars, Journalof Japan Society of Civil Engineers, Ser.B1 (Hydraulic Engineering), Vol. 71, No. 4, pp. I_631-I_636, 2015.

No. 18 pp. 41-49 2007 [Tsuzuki, T., Kodama, Y.,Taki, K. and Goto, T: Restoring the gravel bars of the Ina
River: verifying a hypothesis by experimental river works(interim report), Report of Japan Riverfront research Center, No. 18, pp. 41-49, 2007.]
7)13)
16
pp. 235-240 2010 [Matsuda, K., Uchibori, S., Shimizu, Y., Ishihara, M. and Todo, M.: Study on
riverbed deformation caused by flood disturbance resulting
from channel excavation and forestation control measures
on a stable gravel bars, Advances in River Engineering, Vol.
16, pp. 235-240, 2010.]
8)
21
pp.
217-222 2015 [An effective method for restoring theformer water courses of a river where the water courses arewell established, Advances in River Engineering, Vol. 21,
pp. 217-222, 2010.]
9)18
1
pp. 47-52 2015 [Chibana, T.
and Harada, M.: Effectiveness of comprehensive approaches to macro-scale phenomena in rivers, Ecologicaland Civil Engineering, Vol. 18, No. 1, pp. 47-52, 2015.

B1 Vol. 74 No. 4 I_1441-I_1446 2018 [Akoh, R.,
Maeno, S, Yoshida, K., Takahashi, Y. and Ishikawa, T.:
Study of inundation flow analysis considering small topography and numerical experiment of the Kinu River, Journalof Japan Society of Civil Engineers, Ser.B1 (Hydraulic Engineering), Vol. 74, No. 4, pp. I_1441-I_1446, 2018.]
14)
(I)
41
pp. 1-21 1956 [Iwagaki, Y.: Hydrodynamical study on
critical tractive force, Transaction of the Japan Society ofCivil Engineers, No. 41, pp. 1-21, 1956.]
15)
234
pp. 13-19 1971.
[Tabata, S and Ichinose, H.: An experimental study on critical tractive force of cobble gravels, Journal of the Japan
Society of Erosion Control Engineering, Vol. 23, No. 4, pp.
13-19, 1971.]10)
p. 1-22 1966.

(Received May 31, 2023)(Accepted September 12, 2023)

POSSIBILITY OF GRAVEL RIVERBED RESTORATION BY CHANGING THE
FLOOD REGULATION RULE AT UPSTREAM DAMS --- A CASE STUDY OF
YUDA DAM ON THE UPPER WAGA RIVER --Tadaharu ISHIKAWA and Atsushi KAWACHI
Gravel riverbeds are disappearing due to the growth of forests in river sections downstream from dams
because of the reduction of tractive force by flood control. In this study, the measures to activate riverbed
gravel movement by changing the flood control rule was examined for the Yuda Dam upstream of the Waga
River, a right tributary of the Kitakami River, where the gravel riverbed is remarkably forested. First, it wasconfirmed that the Yuda Dam has sufficient flood control capacity from the statistical analysis of the inflow
to the Yuda Dam and the flow rate of the Waga River at the time of flood as well as the capacity analysisof the downstream channel. Next, the increase in discharge from the dam during floods was examinedwithin the range of the flood flow capacity of the Waga River channel. The result suggested that the riverdischarge with a probability of occurrence of 1/5 can be changed from about 1100 m3/s to 1800 m3/s byincreasing in the minimum flood discharge. Finally, we calculated changes in bed tractive force using ashallow water flow model and showed that the above changes in the flood control rule can increase themobility of 10-cm-diameter pebbles which is dominant in the Waga Riverbed.