ㄽᩥ                                   Ἑᕝᢏ⾡ㄽᩥ㞟➨ᕳᖺ᭶኱ᆺᶍᆺᐇ㦂࡟ࡼࡿᒾ┙ᗋࢆྵࡴἙᗋపୗᑐ⟇࡟㛵ࡍࡿ୍⪃ᐹA STUDY ON THE RIVERBED LOWERING MEASURES, INCLUDING THE BEDROCK FLOOR USING A LARGE MODEL EXPERIMENT∵ᒣᬛኵ1࣭᪫୍ᓅ2࣭⡿ඖ ග᫂3࣭஭ୖ༟ஓ4
Tomoo USHIYAMA, Kazutake ASAHI, Mitsuaki YONEMOTO and Takuya INOUE
1ṇ఍ဨ ᰴᘧ఍♫ Ỉᕤࣜࢧ࣮ࢳ㸦ࠛ062-0933 ໭ᾏ㐨ᮐᖠᕷ㇏ᖹ༊ᖹᓊ3᮲3୎┠2␒7ྕ㸧2ṇ఍ဨ ᕤಟ ୍⯡㈈ᅋἲே ໭ᾏ㐨Ἑᕝ㈈ᅋ㸦ࠛ060-0807 ໭ᾏ㐨ᮐᖠᕷ໭༊໭7᮲す4୎┠5-1㸧
3ṇ఍ဨ ᅜᅵ஺㏻┬ ໭ᾏ㐨㛤Ⓨᒁ ᪫ᕝ㛤Ⓨᘓタ㒊㸦ࠛ078-8513 ໭ᾏ㐨᪫ᕝᕷᐑ๓㏻ᮾ4155␒31㸧
4ṇ఍ဨ ᕤ༤ ᐮᆅᅵᮌ◊✲ᡤ ᐮᆅἙᕝࢳ࣮࣒㸦ࠛ062-8602 ໭ᾏ㐨ᮐᖠᕷ㇏ᖹ༊ᖹᓊ1᮲3୎┠㸧In the Ishikari River, riverbed degradation has been caused by bedrock erosion. Local bedrock erosion
leads to insufficient embedded depth of bridge piers and the damage of revetments. Bedrock that iscompletely covered by alluvium cannot undergo erosion. So, we are planning to be covered the bedrockby gravel in order to suppress the riverbed degradation in the Ishikari River. However, gravel bars formedon the alluvial bed often cause partial bedrock exposure. The purpose of this work is to understand themechanisms underlying the bedrock re-exposure by a large-scale flume experiment. The results suggest
that; 1)bedrock of river banks neighborhood is re-exposed continuously in the longitudinal direction; 2)gravel bars are formed, and the bar height affects partial bedrock exposure; 3) in the straight channel zone,
bedload moves over the exposed bedrock patches; 4) in the meandering zone, secondary flow prevents theintrusion of bedload into the exposed bedrock patches.
Key Words : riverbed degradation, bedrock erosion, alluvial cover, bedrock exposure,a large-scale flume experiment㸯㸬ࡣࡌࡵ࡟
᪫ᕝᕷࢆ㈏ὶࡍࡿ▼⊁ᕝKP157㹼KP166༊㛫࡛ࡣ㸪ᒾ┙౵㣗ࢆక࠺Ἑᗋపୗࡀ㐍⾜ࡋ㸪᪤タㆤᓊࡢᶵ⬟႙ኻࡸᶫ⬮ࡢᏳᐃᛶపୗࡀᠱᛕࡉࢀ࡚࠸ࡿ㸬ᙜヱ༊㛫ࡢᒾ┙ࡣὶ◁ࡢ⾪✺࡟ࡼࡗ࡚౵㣗ࡉࢀࡸࡍ࠸ࡓࡵ1)㸪ᒾ┙ᗋࡢ౵㣗ᢚไࢆ┠ⓗ࡜ࡋࡓそ♟࡜㸪ᤲὶຊపୗࢆ┠ⓗ࡜ࡋࡓపỈ㊰ᣑᖜࡀィ⏬ࡉࢀ࡚࠸ࡿ㸬᪤ ࡢᐇ㦂ⓗ◊✲࡟ࡼࡿ࡜㸪ὶ◁ࡢ⾪✺࡟ࡼࡿᒾ┙౵㣗㏿ᗘࡣ㸪ὶ◁㔞࡟ẚ౛ࡋ1)㸪◁♟⿕そࡢቑຍ࡟࡜ࡶ࡞࠸ῶᑡࡍࡿ2)㸬ࡲࡓ㸪◁♟⿕そࡢ㠃✚ࡣ㸪⤥◁㔞ࡢῶᑡ࡟క࠸⥺ᙧⓗ࡟ቑຍࡍࡿഴྥ࡟࠶ࡿࡀ3)4)㸪ᒾ┙ᗋୖ࡟஺஫◁ᕞࡸᅛᐃ◁ᕞࡀᙧᡂࡉࢀࡿሙྜࡣ㸪ࡑࡢỈ⌮≉ᛶࡸᅵ◁⛣ື≉ᛶ࡟ᛂࡌ࡚㸪⌧㇟ࡀࡼࡾ」㞧໬ࡍࡿࡇ࡜ࡀ▱ࡽࢀ࡚࠸ࡿ3)5)6)7)㸬
ᙜヱ༊㛫࡟࠾࠸࡚ࡶ㸪ᒾ┙ᗋୖ࡟஺஫◁ᕞࡸᅛᐃ◁ᕞࡀᙧᡂࡉࢀ࡚࠾ࡾ㸪ᒾ┙ᗋࢆ◁♟࡛そࡗࡓ㝿ࡢᑐ⟇ຠᯝᅗ▼⊁ᕝ࡟࠾ࡅࡿᒾ┙౵㣗㸦KP161.5km௜㏆㸧ࡸ㸪ᑐ⟇ᐇ᪋ᚋ࡟⏕ࡌࡿ⌧㇟ࡢண ࡀ㞴ࡋ࠸≧ἣ࡟࠶ࡿ㸬ࡑࡇ࡛㸪ᮏ◊✲࡛ࡣ㸪ᒾ┙ᗋࢆ◁♟࡛⿕そࡋࡓ㝿ࡢ෌㟢ฟ⌧㇟࡜Ỉ⌮≉ᛶࡢ㛵ಀࢆ᫂ࡽ࠿࡟ࡍࡿࡓࡵ࡟㸪ᙜヱ༊㛫ࡢ1/50ࡢ኱ᆺỈ⌮ᶍᆺࢆ⏝࠸ࡓᐇ㦂ࢆ⾜࠸㸪ࡑࡢ⤖ᯝࡢ⪃ᐹࢆ⾜ࡗࡓ㸬- 289 -ᅗᐇ㦂ᶍᆺᖹ㠃ᅗ



2.56

KP162.4

2.52
㧗ỈᩜపỈ㊰⾲ᐇ㦂᮲௳

㧗Ỉᩜ

ᶆ㧗(m)

2.48

᮲௳

2.44
2.40
ᒾ┙㧗2.36

ᣑᖜᚋᶓ᩿
ᣑᖜ๓
ᒾ┙⿕そ

2.32
2.28
0

1

2

3

4
㊥㞳(m)

56

78



ᅗึᮇᶓ᩿ᙧ

㸰㸬኱ᆺỈ⌮ᶍᆺᐇ㦂್ഛ⪃ὶ㔞Q (Ɛ/s)35.6ᖹᆒᖺ᭱኱ὶ㔞ᖹᆒἙᗋ໙㓄I

1/299

ᖹᡂ23ᖺ9᭶ὥỈᚋἙᗋᮦᩱ⢏ᚄd (mm)

1.18

60㸣⢏ᚄ

↓ḟඖᤲὶຊȫ*

0.046

KP165.05㹼KP167ᖹᆒ༢఩᫬㛫⤥◁㔞 (Ɛ/10ศ)3.5

ⰱ⏣࣭㐨ୖᘧ

࣐ࢽࣥࢢࡢ⢒ᗘಀᩘn0.0151㏻Ỉ᫬㛫 (hr)30ࡢᙧ≧࡛࠶ࡿࡓࡵ㸪ᣑᖜᚋࡢపỈ㊰㒊ࡣᒾ┙ᗋ࡛࠶ࡿ㸬ᮏ◊✲࡛⏝࠸ࡽࢀࡓᐇ㦂Ỉ㊰ࡣ㸪ᙜヱ༊㛫ࡢ⦰ᑻ1/50ᙜヱ༊㛫࡜ྠࡌ౵㣗㏿ᗘࡢᒾ┙ᗋࢆసᡂࡍࡿࡇ࡜ࡣᅔ㞴ࡢ኱ᆺᶍᆺ࡛࠶ࡿ ᅗ 㸬ࡇࢀࡲ࡛࡟㸪1ࢣ࣮ࢫࡢ⌧ἣ࡞ࡓࡵ㸪ᮏᐇ㦂࡛ࡣᒾ┙ᗋࢆࣔࣝࢱࣝᛶࡢᅛᐃᗋ࡜ࡋࡓ㸬෌⌧ᐇ㦂࡜4ࢣ࣮ࢫࡢᑐ⟇ຠᯝண ᐇ㦂ࢆ⾜ࡗ࡚࠸ࡿ㸬ࡲࡓ㸪㧗ỈᩜࡶⰪࡸ࢔ࢫࣇ࢓ࣝࢺࡀᙇࡽࢀ࡚࠾ࡾ㸪Ṥ࡝ᮏ✏࡛ࡣ㸪ᑐ⟇ຠᯝண ᐇ㦂ࡢ୰ࡢࠕపỈ㊰ᣑᖜ㸩ᒾ┙Ἑᗋኚືࡋ࡞࠸ࡓࡵᅛᐃᗋ࡜ࡋࡓ㸬ࡋࡓࡀࡗ࡚㸪㉥⥺࡛
⿕そ2cm ⌧ᆅ⦰ᑻ1m ࠖࡢࢣ࣮ࢫ࡟ࡘ࠸࡚グ㏙ࡍࡿ㸬♧ࡋࡓᣑᖜᚋᶓ᩿ࡣ඲࡚ᅛᐃᗋ࡛࠶ࡿ㸬そ♟ᚋᶓ᩿ࡣ㸪そ♟ཌࡀ2cm௨ୖ࡜࡞ࡿࡼ࠺࡟タᐃࡋ Ἑᗋపୗᑐ⟇᱌ࡓ㸬ᑠὶ㔞᫬ࡢỈ῝ࢆ☜ಖࡍࡿࡓࡵ࡟㸪⌧ἣ⃢➽㒊ࡀV⌧ᅾ᳨ウࡉࢀ࡚࠸ࡿἙᗋపୗᑐ⟇ࡣ㸪పỈ㊰ᣑᖜ࡜そᏐ࡟࡞ࡿࡼ࠺࡟⿕そࡋ࡚࠸ࡿ㸬ࡲࡓ㸪పỈ㊰ᣑᖜ࠾ࡼࡧ
♟࡛࠶ࡿ ᅗ 㸬◁ᕞ᥀๐࡟ࡼࡾⓎ⏕ࡍࡿᅵ㔞࡜そ♟ᅵ㔞ࡀᴫࡡ➼ࡋࡃ࡞పỈ㊰ᣑᖜࡣ㸪ᤲὶຊࢆపୗࡉࡏ◁♟ࡢὶฟࢆᢚไࡍ
ࡿࡼ࠺࡟タᐃࡉࢀ࡚࠸ࡿࡓࡵ㸪⌧ἣἙ㐨ࡢᖹᆒἙᗋ㧗࡜ࡿࡇ࡜ࢆ┠ⓗ࡜ࡋ࡚࠸ࡿ㸬ᣑᖜᚋࡢపỈ㊰ᖜࡣ㸪ᖹᆒᖺそ♟ᚋࡢᖹᆒἙᗋ㧗ࡣᴫࡡ➼ࡋ࠸㸬᭱኱ὶ㔞ୗ࡟࠾ࡅࡿ↓ḟඖᤲὶຊࢆἙᗋపୗ༊㛫Ἑᗋᮦᩱࡣ㸪ᖹᡂ8ᖺ࠾ࡼࡧᖹᡂ23ᖺࡢἙᗋᮦᩱㄪᰝ
KP160㹼165 ࡢୖୗὶ༊㛫࡜ྠ⛬ᗘ࡜ࡍࡿࡓࡵ࡟ᚲせ⤖ᯝࢆᇶ࡟ᐇ㦂༊㛫࡛࠶ࡿKP160.0㹼165.0༊㛫ࡢᖹᆒⓗ࡞⣙3.2m ⌧ᆅ⦰ᑻ160m ࡛࠶ࡿ㸬࡞⢏ᚄศᕸࡢ1/50࡟⦰ᑻࡋ୚࠼ࡓ㸬そ♟ࡣ㸪㟢ᒾ⟠ᡤࢆῶᑡࡉࡏᒾ┙౵㣗ࢆ㜵ࡄࡇ࡜ࢆ┠ᐇ㦂ὶ㔞ࡣ㸪᪫ᶫỈ఩ὶ㔞ほ ᡤࡢ㐣ཤ30ᖺ㛫 ᫛࿴ⓗ࡜ࡋ࡚࠸ࡿ㸬そ♟ཌࡣ㸪పỈ㊰ᣑᖜ࠾ࡼࡧ◁ᕞ᥀๐࡟53ᖺ࠿ࡽᖹᡂ19ᖺ ࡢᖹᆒᖺ᭱኱ὶ㔞Q 35.6Ɛs ⌧ᆅ⦰ࡼࡾⓎ⏕ࡍࡿ◁♟㔞ࢆ᭱኱㝈฼⏝ࡋ㸪ୟࡘ⌧ἣᖹᆒἙᗋ
ᑻ630m3s ࢆᐃᖖὶ࡛୚࠼ࡓ㸬㧗⛬ᗘ࡜ࡍࡿࡓࡵ࡟ᚲせ࡞⣙2cm ⌧ᆅ⦰ᑻ1m ࡛࠶ࡿ㸬 ୖὶ➃⤥◁㔞ࡣ㸪ⰱ⏣࣭㐨ୖࡢᤲὶ◁㔞ᘧ8)ࡼࡾồࡵࡓ㣬࿴ὶ◁㔞 ᖹ⾮ὶ◁㔞 ࢆィ㔞࢝ࢵࣉ࡛ィ㔞ࡋୖὶ➃ ᐇ㦂᮲௳
KP167.0 ࡢᅛᐃᗋ༊㛫 ᘏ㛗2m ࡼࡾேຊ࡛⤥◁ࡋࡓ㸬ᅗ࡟ึᮇᶓ᩿ᙧࢆ♧ࡍ㸬ᅗ୰ࡢ◚⥺ࡣ⌧ἣἙ㐨 ᖹ
ᡂ23ᖺ 㔞 㸪ᅗ୰ࡢ㯮⥺࡛♧ࡋࡓ㧗ࡉࡣ⦪᩿ⓗ࡞࣮࣎ ほ ᪉ἲࣜࣥࢢㄪᰝࡼࡾุ᫂ࡋࡓᒾ┙ᒙࡢ㧗ࡉ㸪㉥⥺ࡣᣑᖜᚋἙ
㏻Ỉ๓ᚋࡢἙᗋ㧗ኚ໬ࢆᢕᥱࡍࡿࡓࡵ㸪KP159.0㹼㐨㸪㯤Ⰽ⥺ࡀそ♟ᚋἙ㐨 ᐇ㦂ࡢึᮇἙ㐨 ࡛࠶ࡿ㸬
KP165.0༊㛫࡛⦪᩿᪉ྥ100m㛫㝸㸪ᶓ᩿᪉ྥ5mm㛫㝸࡛ᣑᖜᚋᶓ᩿ࡣ㸪ᒾ┙ᒙࡼࡾ㧗࠸◁♟ᒙ㒊ࢆ᥀๐ࡋࡓᚋ ࣮ࣞࢨ࣮◁㠃ィ ᰴ ࢪࣕࢥ࣒〇 ࢆ⏝࠸࡚ ᐃࡋࡓ㸬- 290 -

iRIC࡟ࡼࡾྍど໬ᅗึᮇἙᗋ࠿ࡽࡢኚ໬㔞ࢥࣥࢱ࣮ᅗ㻵㻩㻜㻚㻜㻜㻝㻵㻩㻜㻚㻜㻜㻜㻝 㻵㻩㻜㻚㻜㻝㻵㻩㻜㻚㻜㻜㻝㻵㻩㻜㻚㻜㻝㻵㻩㻜㻚㻜㻜㻜㻝㻵䠖Ỉ㠃໙㓄ᐇ㦂⤖ᯝ㻡㻚㻜㻜◁ᕞ㠀Ⓨ⏕」ิ◁ᕞ༢ิ◁ᕞ䃣㻖㻾

㏻Ỉ๓ᚋࡢ㟢ᒾ㠃✚ࡢኚ໬ࢆᢕᥱࡍࡿࡓࡵ㸪KP159.0
㹼KP165.0༊㛫࡛ࢺ࣮ࢱࣝࢫࢸ࣮ࢩࣙࣥࢆ⏝࠸࡚㟢ᒾ⠊ᅖࡢᗙᶆࢆ ᐃࡋࡓ㸬
㏻Ỉ୰ࡢ⾲㠃ὶἣ࠾ࡼࡧἙᗋࡢὶ◁≧ἣࢆᢕᥱࡍࡿࡓࡵ㸪ࣅࢹ࢜᧜ᙳࢆ⾜ࡗࡓ㸬㻜㻚㻡㻜㸱㸬ᐇ㦂⤖ᯝ㻜㻚㻜㻡㻜㻚㻝

㻝㻚㻜㻝㻜㻚㻜㻝㻜㻜㻚㻜㻝㻜㻜㻜㻚㻜

㻮㻵㻌㻜㻚㻞㻛㼔

ᅗ஺஫◁ᕞࡢᙧᡂ㡿ᇦ༊ศ

2.70

ึᮇἙᗋ㧗

ᒾ┙⥺(H19䞉20䝪䞊䝸䞁䜾ㄪᰝ䜘䜚)ᖹᆒἙᗋ㧗䠄30᫬㛫㏻Ỉᚋ䠅᭱῝Ἑᗋ㧗䠄30᫬㛫㏻Ỉᚋ䠅⌧ἣ᭱῝Ἑᗋ㧗ᒾ┙⿕そ⠊ᅖ

పỈ㊰ᣑᖜ⠊ᅖᖹᆒἙᗋኚ໬㧗䠄30᫬㛫ᚋͲึᮇἙᗋ䠅

2.60

2.40

Ọᒣᶫ
KP164.58

0.14
0.12

໭᪫ᕝ኱ᶫ
KP163.01⛅᭶ᶫ
KP161.08

2.50

0.16
Ọᒣほ ᡤ
KP163.90.10
0.08

ⰼဏ኱ᶫ
KP159.42

2.30

0.06

2.20

0.04

2.10

0.02

2.00

0.00

1.90
㻝㻡㻥㻚㻜㻌㻝㻢㻜㻚㻜㻌㻝㻢㻝㻚㻜㻌

㻝㻢㻞㻚㻜㻌
࣏࢟ࣟࢫࢺ㻝㻢㻟㻚㻜㻌

㻝㻢㻠㻚㻜㻌

Ἑᗋኚ໬㧗䠄m䠅

2.80

ᶆ㧗䠄m䠅

 ᑐ⟇ᚋࡢἙᗋᙧែ
ᅗ࡟♧ࡍࡼ࠺࡟㸪ᐇ㦂㏻ỈᚋࡢἙᗋࡣపỈ㊰୰ᚰ㒊࡛ሁ✚ഴྥ㸪Ἑᓊ㝿࡛పୗഴྥࡀぢࡽࢀࡿ㸬ᙧᡂࡉࢀࡓ
◁ᕞࡢἼ㛗ࡣ᭱ప16m㸪᭱኱32m㸪ᖹᆒ28m⛬ᗘ㸪Ἴ㧗
ࡣ᭱ప3cm㸪᭱኱8.4cm㸪ᖹᆒ6cm⛬ᗘ࡛࠶ࡗࡓ㸬㏻Ỉ୰ࡢỈ఩࠾ࡼࡧ㏻ỈᚋࡢἙᗋ㧗࠿ࡽ୰つᶍἙᗋᙧែࡢ㡿ᇦ༊ศ9)ࢆᩚ⌮ࡍࡿ࡜㸪ᅗ࡟♧ࡍࡼ࠺࡟༢ิ◁ᕞ࠿ࡽ」ิ◁ᕞࡢ㡿ᇦ࡟༊ศࡉࢀ㸪Ἑᗋపୗ༊㛫ࡢୖୗὶࡢ♟ᗋ༊㛫࡜ྠᵝࡢἙᗋᙧែ࡛࠶ࡿ
 Ἑᗋ㧗ኚ໬ᅗ࡟♧ࡍࡼ࠺࡟㸪ึᮇἙᗋ࠿ࡽࡢἙᗋኚ໬㧗ࢆࡳࡿ࡜ᖹᆒἙᗋ㧗ࡣኚ໬㔞ࡀᑠࡉࡃᴫࡡᏳᐃഴྥ࡛࠶ࡿ㸬ࡲࡓ㸪ᐇ㦂ᚋࡢ᭱῝Ἑᗋ㧗ࡣ⌧ἣ᭱῝㒊ࡲ࡛ࡣపୗࡋ࡞
࠿ࡗࡓ㸬ࡇࢀࡽࡢࡇ࡜࠿ࡽ㸪పỈ㊰ᣑᖜ࡟ࡼࡗ࡚そ♟ᅵ◁ࡀ⥔ᣢࡉࢀ㸪Ἑᗋపୗࢆᢚไ࡛ࡁࡿࡇ࡜ࡀ☜ㄆࡉࢀࡓ㸬

Ͳ0.02
㻝㻢㻡㻚㻜㻌ᅗἙᗋ⦪᩿ᅗỈⰍࡢ㒊ศࡀ㟢ᒾ⟠ᡤ ᒾ┙㟢ฟそ♟ᅵ◁ࡣ⥔ᣢࡉࢀࡿࡶࡢࡢ㸪◁ᕞࡢⓎ㐩࡟ࡼࡾᒾ┙ᗋ ࣔࣝࢱࣝᗋ ࡢ㟢ฟࡍࡿ⟠ᡤࡀ☜ㄆࡉࢀࡓ㸬ᅗ㸪ᅗ࡟♧ࡍࡼ࠺࡟そ♟ཌࡀ◁ᕞἼ㧗ࡼࡾⷧ࠸Ἑᓊ㝿ࡀ㟢ฟࡍࡿഴྥ࡛࠶ࡗࡓ㸬㏻Ỉ࠿ࡽ15᫬㛫⛬ᗘࡲ࡛ࡣ㸪ࣃࢵࢳ≧࡛࠶ࡗࡓ㟢ᒾࡀ㸪ᚎࠎ࡟ᗈࡀࡾ⦪᩿ⓗ࡟㐃⥆ࡋࡓ㸬ࡓࡔࡋ㸪㟢ᒾ㠃✚ࡣᅗ࡟♧ࡍࡼ࠺࡟ᑐ⟇๓ ⌧ἣἙ㐨 ࡟ẚ࡭ᑐ⟇ᚋ ᐇ㦂ᚋ ᪉ࡀ5๭௨ୖῶᑡࡍࡿ⤖ᯝ࡜࡞ࡗࡓ㸬ᅗ㟢ᒾ≧ἣ㸦KP162.0௜㏆㸧 㟢ᒾ⟠ᡤࡢὶ◁᭷↓㟢ᒾ⟠ᡤ࡟࠾࠸࡚ࡣ㸪ᅗ࡟♧ࡍࡼ࠺࡟㸪ὶ◁ࡀ࠶ཌࡀⷧ࠸పỈ㊰ᣑᖜ⟠ᡤ࡛㟢ᒾࡋ࡚࠸ࡿ㸬㟢ᒾ⟠ᡤ࡛ὶࡿ⟠ᡤ㸪ὶ◁ࡀ࡯࡜ࢇ࡝࡞࠸⟠ᡤࡀ☜ㄆࡉࢀࡓ㸬◁ࡀ࠶ࡿ⟠ᡤࡣ┤⥺㒊࡟ከࡃ㸪ὶ◁ࡀ࡯࡜ࢇ࡝࡞࠸⟠ᡤࡑࡇ࡛㸪㟢ᒾ⟠ᡤ࡟࠾ࡅࡿὶ◁ࡢ᭷↓ࢆศᯒࡋࡓ㸬ὶ◁
ࡣ‴᭤㒊እᓊ࡟ከ࠿ࡗࡓ㸬ᐇ㦂୰㸪㟢ᒾࡋ࡚࠸ࡿ‴᭤㒊ࡢ᭷↓ࡣ㸪㏻Ỉ୰࡟2᫬㛫ẖ࡟᧜ᙳࡋࡓὶἣࣅࢹ࢜࠿ࡽ
እᓊ࡛ᐇ㦂◁ࢆᩓᕸࡋ࡚ࡳࡿ࡜㸪Ἑ㐨ෆᓊ࡬ὶࢀࡿࡢࡀุㄞࡋࡓ㸬ᅗ࡟♧ࡍࡼ࠺࡟㸪‴᭤㒊እᓊࡸึᮇ⿕そ☜ㄆࡉࢀࡓ㸬- 291 -

㏻Ỉ5᫬㛫ᚋ㏻Ỉ10᫬㛫ᚋ㏻Ỉ15᫬㛫ᚋ㏻Ỉ20᫬㛫ᚋ㏻Ỉ30᫬㛫ᚋỈⰍ㒊ศࡀ㟢ᒾ⟠ᡤᅗ┠ど࡛☜ㄆࡋࡓ㟢ᒾ≧ἣ᫬⣔ิኚ໬ᑐ⟇๓㟢ᒾ㠃✚㸸Pᐇ㦂ึᮇ㸦そ♟㸧ᑐ⟇ᚋ㟢ᒾ㠃✚㸸P㟷Ⰽ㒊ศࡀ㟢ᒾ⟠ᡤᅗᒾ┙㟢ฟ⟠ᡤᖹ㠃ᅗ- 292 -‴᭤㒊ୗὶ㸸࡯࡜ࢇ࡝ὶ◁ࡀὶࢀ࡚࠸࡞࠸┤⥺㒊㸸ὶ◁ࡀ⦪᩿ⓗ࡟㐃࡞ࡗ࡚ὶࢀ࡚࠸ࡿ

ᅗᒾ┙ୖࡢὶ◁ࡢ᭷↓ձղճմյն‫ ڦ‬ὶ◁࡞ࡋ‫ ڦ‬ὶ◁࠶ࡾᅗ㟢ᒾ⟠ᡤุᐃ⤖ᯝ㸦㏻Ỉ᫬㛫ᚋ㸧ࡀ⦪᩿ⓗ࡟㐃⥆ࡋࡓせᅉ࡜ࡋ࡚⪃࠼ࡽࢀࡿࡢࡣᒾ┙ᗋ࡜◁♟ᗋࡢ⢒ᗘࡢ㐪࠸࡛࠶ࡿ㸬▼⊁ᕝࡢ㟢ᒾ༊㛫࡟࠾࠸࡚㸪ᒾ┙ᗋࡢ⢒ᗘࡣ◁♟ᗋࡢ⢒ᗘࡼࡾప࠸ࡓࡵ1)㸪ᮏ◊✲࡛ ᒾ┙ᗋୖ࡟ᙧᡂࡉࢀࡿ⮬⏤◁ᕞ࡜㟢ᒾ⟠ᡤ⏝࠸ࡓࣔࣝࢱࣝᗋࡢ⢒ᗘࡶ◁♟ᗋࡢ⢒ᗘࡼࡾపࡃタᐃࡋᒾᗋୖ࡟ᙧᡂࡉࢀࡿ⮬⏤◁ᕞ࡟ࡘ࠸࡚ࡣ㸪ࡇࢀࡲ࡛࡟࡚࠸ࡓ㸬ࡇࡢࡓࡵ㸪㟢ᒾࣃࢵࢳࡀฟ᮶ࡿ࡜㸪Ỉ㊰ࡢྜᡂ࠸ࡃࡘ࠿ࡢ◊✲ࡀ⾜ࢃࢀ࡚࠾ࡾ㸪ᕝᖜỈ῝ẚࡀ኱ࡁࡃ㸪⢒ᗘࡣపୗࡍࡿ㸬⢒ᗘࡀపୗࡍࡿ࡜㝈⏺ᤲὶຊࡣపୗࡋ1)⤥◁㔞ࡀ㣬࿴ὶ◁㔞 ࡑࡢἙ㐨ࡀὶࡋ࠺ࡿὶ◁㔞 ࡟㏆ࡃ㸪 㸪⤖ᯝⓗ࡟Ỉ㊰඲యࡢ㣬࿴ὶ◁㔞ࡣቑຍࡍࡿ10)㸬ୖὶἙᗋ໙㓄ࡀ⦆࠸ሙྜ㸪ᒾᗋୖ࡟ࡶ◁ᕞࡀⓎ⏕ࡍࡿࡇ࡜ࡀ➃࡛ࡣ◁♟ᗋࢆ᝿ᐃࡋࡓ㣬࿴ὶ◁㔞ࢆ⤥◁㔞࡜ࡋ࡚୚࠼3)ᐇ㦂࡟ࡼࡾ☜ㄆࡉࢀ࡚࠸ࡿ ᅗ 㸬ࡲࡓ㸪⤥◁㔞࡜㣬࡚࠸ࡓࡓࡵ㸪㟢ᒾࡢቑຍ࡟క࠸㣬࿴ὶ◁㔞ࡀቑຍࡍࡿ࡜㸪࿴ὶ◁㔞ࡢẚࡀᑠࡉࡃ࡞ࡿ࡜㸪◁ᕞࡢἼ㛗ࡀ㛗ࡃ࡞ࡿࡇ⤥◁㔞㣬࿴ὶ◁㔞ࡢẚࡣపୗࡋ㸪⤖ᯝⓗ࡟㛗࠸Ἴ㛗ࡢ5)6)◁ᕞࡀⓎ㐩ࡋ㟢ᒾ⟠ᡤࡀ㐃⥆ࡋࡓ࡜᥎ ࡉࢀࡿ㸬࡜ࡀ⌮ㄽⓗ◊✲ ࠾ࡼࡧᩘ್ゎᯒⓗ◊✲ ࡟ࡼࡗ࡚ᣦ᦬ࡉࢀ࡚࠸ࡿ㸬▼⊁ᕝࡢࡼ࠺࡟㸪ᒾ┙ᗋࡢ⢒ᗘࡀ◁♟ᗋࡢ⢒ᗘࡼࡾపᮏᐇ㦂ࡢᕝᖜỈ῝ẚࡣ29㹼156⛬ᗘ࠶ࡾ㸪㯮ᮌ࣭ᓊࡢ࠸ᒾ┙Ἑᕝࡣከ࠸㸬ࡇࡢࡼ࠺࡞ᒾ┙Ἑᕝ࡛ࡣ㸪そ♟ࢆࡋ୰つᶍἙᗋᙧែࡢ㡿ᇦ༊ศᅗ9)࡟ࡼࢀࡤ㸪஺஫◁ᕞⓎ⏕࡚ࡶ㸪୍ᗘᒾ┙ࡀ㟢ฟࡍࡿ࡜㸪◁ᕞἼ㛗ࡀఙࡧ㸪㟢ᒾ㠃㡿ᇦ࡜」ิ◁ᕞⓎ⏕㡿ᇦࡢ㛫࡟఩⨨ࡍࡿ㸬ࡇࡢࡓࡵ㸪ᐇ✚ࡀቑ኱ࡍࡿྍ⬟ᛶࡀ㧗࠸㸬ࡇࡢࡼ࠺࡞ᒾ┙Ἑᕝ࡟そ♟㦂ࡢึᮇẁ㝵 ඲㠃◁♟ᗋ≧ែ ࡟࠾࠸࡚㸪◁ᕞࡀⓎ⏕ࡋࢆ⾜࠺ሙྜࡣ㸪ᒾ┙ࡀ㟢ฟࡋ࡞࠸ࡼ࠺࡟㸪◁ᕞ㧗௨ୖࡢࡓ㸬ࡑࡢᚋ㸪◁ᕞἼ㧗ࡢⓎ㐩࡟క࠸㸪ࣃࢵࢳ≧ࡢ㟢ᒾ⟠そ♟ཌࢆ☜ಖࡍࡿࡇ࡜ࡀ㔜せ࡜⪃࠼ࡽࢀࡿ㸬ᡤࡀそ♟ཌࡢⷧ࠸ᕥྑᓊ࡟⌧ࢀࡓ㸬ᮏᐇ㦂࡛ࡣ㸪㣬࿴ὶ◁㔞࡜➼ࡋ࠸⤥◁㔞ࢆୖὶ➃࡟୚࠼࡚࠸ࡓࡵ㸪ᐇ㦂㛤ጞ 㟢ᒾ⟠ᡤ࡜ὶ◁ࡢ᭷↓๓ࡢᐃᛶⓗ࡞ண ࡛ࡣ㸪◁ᕞἼ㛗ࡣఙࡧࡎ㸪ࣃࢵࢳ≧ࡢከࡃࡢᒾ┙Ἑᕝ࡟࠾࠸࡚㸪ᒾ┙ᗋࡣ୺࡟ὶ◁ࡢ⾪✺࡟㟢ᒾ⟠ᡤࡀ㸪◁ᕞࡢ⛣ື࡟క࠸㸪ୗὶ࡟⛣ືࡋ࡚࠸ࡃ࡜ࡼࡗ࡚౵㣗ࡉࢀࡿ㸬Chatanantavet and Parker11)࡟ࡼࢀࡤὶ
⪃࠼࡚࠸ࡓ㸬ࡋ࠿ࡋ㸪ᐇ㝿࡟ࡣ᫬㛫ࡢ⤒㐣࡟క࠸㸪◁ᕞ◁ࡢ⾪✺࡟ࡼࡿ౵㣗㏿ᗘࡣ㸪௨ୗࡢᘧ࡛⾲ࡉࢀࡿ㸬Ἴ㛗ࡀᘏఙࡋ㸪㟢ᒾࣃࢵࢳࡀ⧅ࡀࡾ㸪⦪᩿ⓗ࡟㐃⥆ࡋࡓ
E E qb Fe(1)㟢ᒾ⟠ᡤࢆᙧᡂࡋࡓ㸬⤥◁㔞ࡀ㣬࿴ὶ◁㔞࡟➼ࡋ࠸࡟ࡶ㛵ࢃࡽࡎ㸪㟢ᒾ⟠ᡤࡇࡇ࡛㸪Eࡣ౵㣗㏿ᗘ㸪ȕࡣᦶ⪖ಀᩘ㸪qbࡣὶ◁㔞㸪Feࡣ㸲㸬⪃ᐹ- 293 -⾲㟢ᒾ⟠ᡤࡢ᭤⋡༙ᚄ㸦పỈ㊰ࢭࣥࢱ࣮㸧༊㛫ุᐃ

ձKP159.2㹼160.1

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16.2 (810)ղKP160.1㹼160.8
ճKP160.8㹼161.5
մKP161.5㹼162.5
յKP162.5㹼164.0
նKP164.0㹼164.8

ὶ◁࠶ࡾ
ὶ◁࡞ࡋ
ὶ◁࠶ࡾ
ὶ◁࠶ࡾ
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109.6 (5,480)
16.6 (830)34.6 (1,730)
48.6 (2,430)
16.4 (820)᭤⋡༙ᚄm ⌧ᆅ⦰ᑻ㟢ᒾ㠃✚⋡ ᏶඲࡞㟢ᒾᗋࡢሙྜ1㸪᏶඲࡞◁♟ᗋࡢሙྜ
0 ࡛࠶ࡿ㸬ࡘࡲࡾ㸪᏶඲࡟㟢ᒾࡋ࡚࠸࡚ࡶὶ◁ࡀ࡞࠸⟠ᡤ࡛ࡣ㸪ὶ◁࡟ࡼࡿ౵㣗ࡣⓎ⏕ࡋ࡞࠸࡜⪃࠼ࡽࢀࡿ㸬ᅗ࡟ࡼࡿ࡜㸪㟢ᒾࡋ࡚࠾ࡾὶ◁ࡀ࠶ࡿ⟠ᡤࡣ㸪Ἑ㐨ࡀ┤⥺࡟㏆࠸༊㛫࡟ከࡃ㸪㟢ᒾࡋ࡚࠸ࡿࡀὶ◁ࡀ↓࠸⟠ᡤࡣ㸪Ἑ㐨ࡀ‴᭤ࡋ࡚࠸ࡿ༊㛫ࡢእᓊ࡟ከ࠸㸬ᅗ࡟♧ࡋࡓ㉥ࣃࢵࢳ༊㛫࡜⣸ࣃࢵࢳ༊㛫ࡢἙ㐨ࡢ᭤⋡༙ᚄࢆ⟬ฟࡍࡿ࡜ ⾲ 㸪᭤⋡༙ᚄࡀ20m ⌧ᆅ⦰ᑻ1000m
௨ୗࡢ㟢ᒾ㒊࡟ࡣὶ◁ࡀ࠶ࡿࡀ㸪᭤⋡༙ᚄࡀ20m ⌧ᆅ⦰ᑻ1000m ௨ୖࡢ㟢ᒾ㒊࡟ࡣὶ◁ࡀ↓࠸ࡇ࡜ࡀ☜ㄆࡉࢀࡓ㸬‴᭤㒊እᓊ࡛ࡣ㸪஧ḟὶࡢᙳ㡪࡟ࡼࡗ࡚㸪Ἑᗋ㏆ഐ࡟እᓊ࠿ࡽෆᓊ࡟ྥ࠿࠺ὶࢀࡀ⏕ࡌࡿ㸬㏻ᖖࡢ◁♟Ἑᗋࡢሙྜ㸪ࡇࡢὶࢀ࡟ࡼࡗ࡚㸪እᓊࡢ◁♟ࡀෆᓊ࡬⛣ືࡋ㸪እᓊഃࡢ῝࠸᥀ࢀࡀᙧᡂࡉࢀࡿ㸬ᒾ┙ᗋࡢሙྜ㸪୍ᗘᒾ┙ࡀ㟢ฟࡍࡿ࡜㸪ࡑࡇ࠿ࡽὶ◁ࡣ⏕ࡌ࡞࠸㸬ࡲࡓ㸪ୖὶ࠿ࡽὶࢀ㎸ࡴ◁♟ࡣ㸪እᓊഃࡢ㟢ᒾ༊㛫࡟฿㐩ࡍࡿ๓࡟ෆᓊ࡟ᐤࡏࡽࢀࡿ㸬ࡇࡽࢀࡢ⤖ᯝ㸪‴᭤㒊እᓊ࡟ὶ◁ࡢ↓࠸㟢ᒾ༊㛫ࡀ⏕ࡌࡓ࡜᥎ ࡉࢀࡿ㸬  ᮏ◊✲ࡢ㝈ᐃᮏ◊✲࡛ࡣ㸪㠀౵㣗ᛶࡢࣔࣝࢱࣝᗋࢆ⏝࠸࡚ᐇ㦂ࢆ⾜ࡗ࡚࠸ࡿ㸬ࡲࡓ㸪ᐇ㦂ὶ㔞ࡶ୍ᐃ࡛࠶ࡿ㸬ᐇ㝿ࡢᒾ┙Ἑᕝࡢሙྜ㸪ᒾ┙౵㣗ࡸὶ㔞ࡢኚື࡟ࡼࡗ࡚ὶἣࡀኚ໬ࡋ㸪㟢ᒾ⟠ᡤࡸ◁ᕞᙧ≧ࡀኚ໬ࡍࡿྍ⬟ᛶࡀ࠶ࡿ㸬ࡇࡢᙳ㡪ࡘ࠸࡚ࡣ㸪௒ᚋ㸪┤⥺Ỉ㊰ࢆ⏝࠸ࡓᇶ♏ⓗ࡞ᐇ㦂࡟ࡼࡾ☜ㄆࡋ࡚࠸ࡃணᐃ࡛࠶ࡿ㸬㸳㸬ࡲ࡜ࡵἙ㐨┤⥺㒊ࡢ㟢ᒾ⟠ᡤ࡛ࡣ➽≧࡟࡞ࡗ࡚ὶ◁ࡀὶࢀࡿ ୍᪉㸪‴᭤㒊እᓊࡢ㟢ᒾ⟠ᡤࡣ஧ḟὶࡢᙳ㡪࡟ࡼࡾὶ◁ࡀὶࢀ࡚ࡇ࡞࠸᪤ ◊✲1)࠿ࡽ⌧ᆅࡢᒾ┙ࡣὶ◁࡟ࡼࡾὙ᥀ࡉࢀࡿࡇ࡜ࡀ☜ㄆࡉࢀ࡚࠸ࡿ㸬そ♟ࡋࡓ࡜ࡋ࡚ࡶἙᓊ㝿ࡀ㟢ᒾࡍࡿࡇ࡜ࡣ㸪Ἑᓊ㝿࡟⃢➽ࡀᙧᡂࡉࢀࡿྍ⬟ᛶࢆ♧ࡍࡶࡢ࡛࠶ࡿ㸬୍᪉㸪㟢ᒾ㒊࡛ὶ◁ࡀᑡ࡞࠸ࡇ࡜ࡣ㸪ᒾ┙Ὑ᥀ࡀ㐍⾜ࡋ࡙ࡽ࠸ࡇ࡜ࢆ♧ࡍ⤖ᯝ࡛ࡶ࠶ࡿ㸬ࡲࡓ㸪㟢ᒾ⟠ᡤ ὶ◁ࡢ↓ࡋ ࡣ㸪஧ḟὶ࡜㛵㐃ࡢ῝࠸Ἑ㐨᭤⋡࡟ࡼࡗ࡚᥎ᐃ࡛ࡁࡿࡇ࡜ࡀ♧၀ࡉࢀࡓ㸬௒ᚋ㸪ᮏ◊✲࡛ᚓࡽࢀࡓ▱ぢࢆ㋃ࡲ࠼㸪ࡼࡾຠᯝⓗ࡞Ἑᗋపୗᑐ⟇ᕤ࡟ࡘ࠸᳨࡚ウࢆ⾜ࡗ࡚࠸ࡁࡓ࠸㸬ㅰ㎡㸸ᮏ◊✲࡟࠶ࡓࡗ࡚㸪໭ᾏ㐨኱ᏛࡢἨ඾ὒඛ⏕㸪ΎỈᗣ⾜ඛ⏕㸪໭ぢᕤᴗ኱ᏛࡢΏ㑔ᗣ⋞ඛ⏕㸪NPOἲே⎔ቃ㜵⅏⥲ྜᨻ⟇◊✲ᶵᵓࡢ㯮ᮌᖿ⏨ඛ⏕㸪ᅜᅵᢏ⾡ᨻ⟇⥲ྜ◊✲ᡤࡢ᭹㒊ᩔᐊ㛗ࢆࡣࡌࡵࡓࡃࡉࢇࡢ᪉࡟ࡈຓゝࢆ㡬ࡁࡲࡋࡓ㸬ࡇࡇ࡟グࡋ࡚ㅰពࢆ⾲ࡋࡲࡍ㸬ཧ⪃ᩥ⊩1)஭ୖ༟ஓ㸪Ἠ඾ὒ㸪⡿ඖග᫂㸪᪫୍ᓅ㸸㌾ᒾୖࡢ㝈⏺ᤲὶຊ࡜㌾ᒾࡢὙ᥀㏿ᗘ࡟㛵ࡍࡿᐇ㦂㸪Ἑᕝᢏ⾡ㄽᩥ㞟㸪➨17ᕳ㸪
77-82㸪2011㸬
2)Sklar, L. S., and W. E. Dietrich㸸A mechanistic model for river
incision into bedrock by saltating bed load, Water Resour. Res., 40,W06301, 2004.
3)Chatanantavet, P., and Parker, G.㸸Experimental study of bedrock
channel alluviation under varied sediment supply and hydraulicconditions, Water Resour. Res., 44, W12446, 2008.
4)⏣୰ᓅ, Ἠ඾ὒ㸸㒊ศⓗ࡟そ♟ࡋࡓᒾ┙Ἑᗋ࡟࠾ࡅࡿᤲὶ◁㔞࡜ὶࢀࡢ᢬ᢠ๎, ᅵᮌᏛ఍ㄽᩥ㞟 B1(ỈᕤᏛ), Vol. 69, No. 4,
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6)஭ୖ༟ஓ㸪ΎỈᗣ⾜㸪Gary Parker㸪ᒣཱྀ㔛ᐇ㸪ఀ⸨୹㸸⤥◁㔞࡜ᒾᗋ౵㣗ᆅᙧࡢ㛵ಀ㸪ᅵᮌᏛ఍ㄽᩥ㞟B1(ỈᕤᏛ)㸪
Vol.70㸪No.4㸪I_1039-I_1044㸪2014㸬7)᪩ᕝ ༤㸸ᒅᢡ⺬᭤ࡍࡿᒾᗋἙᕝ࡟࠾ࡅࡿ◁ࣞ࢟ሁࡢ⛣ື೵Ṇ᮲௳㸪໭ᾏ㐨Ἑᕝ㈈ᅋ ◊✲ᡤ⣖せ(XXI)㸪2010.

8)ⰱ⏣࿴⏨㸪㐨ୖṇつ㸸⛣ືᗋὶࢀࡢ᢬ᢠ࡜ᤲὶ◁㔞࡟㛵ࡍࡿᮏ◊✲࡛ࡣ㸪ᒾ┙ᗋࡢ౵㣗ࢆక࠺Ἑᗋపୗࢆᢚไࡍࡿ
ᇶ♏ⓗ◊✲㸪ᅵᮌᏛ఍ㄽᩥሗ࿌㞟㸪➨206ྕ, pp.59-69, 1972.
ࡓࡵࡢᑐ⟇᪉ἲࢆ᳨ウࡍࡿࡓࡵ࡟㸪▼⊁ᕝ㟢ᒾ༊㛫ࡢ⦰9)㯮ᮌᖿ⏨㸪ᓊຊ㸸୰つᶍἙᗋᙧែࡢ㡿ᇦ༊ศ࡟㛵ࡍࡿ⌮ㄽⓗᑻ1/50ࡢ኱ᆺᶍᆺỈ㊰ࢆ⏝࠸࡚ᐇ㦂ࢆ⾜ࡗࡓ㸬ࡇࡢ⤖ᯝ㸪 ◊✲㸪ᅵᮌᏛ఍ㄽᩥሗ࿌㞟㸪➨ 342ྕ㸪87-96㸪1984.
పỈ㊰ᣑᖜ࠾ࡼࡧそ♟࡟ࡼࡾ㸪Ἑᗋపୗࢆᢚไ࡛ࡁࡿࡇ10)஭ୖ༟ஓ㸪ఀ⸨୹㸸㌾ᒾἙᗋ࡟࠾ࡅࡿ⢒ᗘ㸪↓ḟඖ㝈⏺ᤲ࡜ࡀ☜ㄆࡉࢀࡓ㸬ࡉࡽ࡟㸪そ♟ᚋ࡟⏕ࡌࡿ⌧㇟࡜ࡋ࡚௨ὶຊ࡜㣬࿴ὶ◁㔞ࡢ㛵ಀ㸪➨68ᅇᅵᮌᏛ఍ᖺḟㅮ₇఍ሗ࿌㞟㸪ୗࡀ☜ㄆࡉࢀࡓ㸬
ϩ-072, 2013㸬 ᒾ┙ࢆそ♟ࡋࡓ࡜ࡋ࡚ࡶ㸪Ἑᓊ㝿ࡀ⦪᩿ⓗ࡟㟢ᒾ11)Chatanantavet, P., and Parker, G.㸸Physically based modeling ofࡍࡿഴྥ࡟࠶ࡿ
bedrock incision by abrasion, plucking, and macroabrasion, J.
 ᑐ⟇ᚋࡢἙ㐨࡟ࡣ◁ᕞࡀᙧᡂࡉࢀ㸪ࡑࡢἼ㧗࡜Ἑ
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ᓊ㝿ࡢ㟢ᒾ࡟ࡣ㛵ಀࡀ࠶ࡿ㸦ཷ௜㸧
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