北海道地区自然災害科学資料センター報告
Vol.36, 85-93, 2023

໭ᾏ㐨ࡢࡢἙᕝ࡟࠾ࡅࡿ㏆ᖺࡢἙ㐨⅏ᐖ࡟࡟ࡘ࠸࡚(2016 ᖺ༑຾ᕝỈỈ⣔࣌࣌ࢣࣞ࣋ࢶᕝἙἙ㐨⅏ᐖࡢࡢ౛)Recent River Channel Disasters and Their Countermeasures inHokkaido, JapanΎỈᗣᗣ⾜ 11㸪໭ᾏ㐨኱ᏛᕤᏛ㝔ᕤᏛ◊✲㝔Yasuyuki Shhimizu11㸪Faculty of Engineering, Hokkaido University

Abstract
In August 2016, Hokkaido region of Japan was exposed to record breaking precipitation
by four typhoons. The Pekerebetsu river which is a tributary of Tokachi river in Easternpart of Hokkaido, a comparatively small river, was worst affected after facing the lasttyphoon. The width of the river expanded from two to five times overnight. In this study,
the authors conducted several field surveys, and followed by performing numericalcalculations to analyze the erosion and deposition phenomena. The results showed that
although overall the river width widened significantly, the situation of the channel
deformation was different between the upstream and downstream. This article describes
the recent trend of the river channel disasters in the rivers in Hokkaido
Key Words: Meandering, flood disaster, record breaking precipitation, bed rock exposure࣮࣮࢟࣡ࢻ㸸⺬⾜, ὥỈ⅏ᐖ, ᪤ ᭱኱㝆㞵, ᒾ┙㟢ฟ1㸬ᴫせ2016 ᖺ 8 ᭶㸪໭ᾏ㐨࡟㐃⥆ࡋ࡚฿᮶ࡋࡓ 4 ࡘࡢྎ㢼 1) ࡟ࡼࡾ㸪༑຾⟶ෆ࡛ࡣᖺ㛫㝆Ỉ㔞ࡢ
⣙ 2 ศࡢ 1 ࡟┦ᙜࡍࡿ⥲㞵㔞 500mm ࢆ㉺࠼ࡿ㞵㔞ࢆほ ࡋࡓ㸬ࡇࡢ㝆㞵࡟ࡼࡾ㸪༑຾⟶ෆࡢከࡃࡢἙᕝ࡛ࡣィ⏬㧗Ỉࢆ㉸࠼ࡿ᪤ ᭱኱ὶ㔞ࢆほࡋ㸪ὶ㊰ࡢ⺬⾜໬࡟క࠺ἙᓊḞቯ㸪ⴠᶫ㸪㐨㊰ᔂⴠ㸪ỏ℃㸪ᾐỈ⿕ᐖ➼ࡀ⏕ࡌࡓ㸬࡞࠿࡛ࡶ㸪ΎỈ⏫ࢆὶࢀࡿ࣌ࢣࣞ࣋ࢶᕝ㸦ᅗ-1㸧࡟࠾ࡅࡿ⿕ᐖつᶍࡣ኱ࡁࡃ㸪1 ᬌ࡛ᕝᖜࡀ 3~5 ಸ⛬ᗘࡲ࡛ᣑᖜ㸦⣙ 35m ࠿ࡽ⣙ 150m ࡞࡝㸧ࡋ㸪Ἑᕝ஦ᴗ༊㛫㸦඲㛗 4.7km㸧ࡢୖὶഃ࡛ࡣ኱つᶍ࡟Ἑᗋపୗࡋ㸪ୗὶഃ࡛ࡣẚ㍑ⓗ┤⥺ⓗ࡟ᩚഛࡉࢀࡓὶ㊰ࡀ኱ࡁࡃ⺬⾜ࡍࡿࡇ࡜࡛ᕥྑᓊࡢ㐃⥆ⓗ࡞ἙᓊḞቯࡀ⏕ࡌ㸪ᶫྎ⿬ࡢὙ᥀࡟క࠺ⴠ
ᶫ㸪ᐙᒇὶኻ㸪ᕷ⾤ᆅࡢᾐỈ➼ࡢ⿕ᐖࡀ⏕ࡌࡓ㸦ᅗ-2㸧㸬ࡇࡢࡼ࠺࡞ᛴ⃭࡞ὶ㊰ኚືࡣ㸪ィ⏬つᶍ௨ୖࡢὶ㔞࡟క࠺኱㔞ࡢᅵ◁ࡢ⛣ື࡟ࡼࡾ㸪Ἑ㐨ࡀእຊ࡟⪏࠼ࡽࢀࡎ࡟኱つᶍ࡟ᣑᖜࡋ㸪ὶ㊰ኚືࡀ⏕ࡌࡓࡶࡢ࡜⪃࠼ࡽࢀࡿ㸬

2㸬࣌ࢣࣞ࣋ࢶᕝ࡟࠾ࡅࡿ⅏ᐖ࣭⿕⿕⅏≧≧ἣࡢᢕᥱ࣌ࢣࣞ࣋ࢶᕝ࡛ࡣୖὶࡢ⿕⅏༊㛫࡜ୗὶࡢ⿕⅏༊㛫࡟࠾࠸࡚␗࡞ࡿὶ㊰ኚື≉ᛶࡀㄆࡵࡽࢀ85ࡓ㸬ࡇࡇ࡛ࡣྛࠎࡢ⿕⅏༊㛫࡟ࡘ࠸࡚㸪⅏ᐖ࣭⿕⅏≧ἣࢆᩚ⌮ࡍࡿ㸬ᅗ1࣌ࢣࣞ࣋ࢶᕝᕷ⾤ᆅ௜㏆ࡢ≧ἣ((2016/9/22 ᧜ᙳ㸪໭ᾏ㐨Ἑᕝ㈈ᅋ᧜ᙳ))ᅗ࣌ࢣࣞ࣋ࢶᕝࡢฟỈ๓ᚋࡢ≧ἣ㸪ୖᅗ㸧ฟỈ๓((2014/7 ᧜ᙳ))㸪ୗᅗ㸧ฟỈᚋᅗୖὶഃࡢ⿕⅏༊㛫ࡢ≧ἣ[[a) ฟỈ๓ᚋࡢὶ㊰఩⨨((㉥⥺㸸⅏ᐖ๓ࡢὶ㊰ࢆ♧ࡍ)),b) ᩚഛ᫬ࡢ≧ἣ,, c)) ฟỈᚋࡢ≧ἣ((2016/11/17 ᧜ᙳ))]ᅗୗୗὶഃࡢ⿕⅏༊㛫ࡢ≧ἣ,, a) ฟỈ๓ᚋࡢὶ㊰఩⨨((㉥⥺㸸⅏ᐖ๓ࡢὶ㊰ࢆ♧ࡍ)),b) ▼ᒣᶫࡢᶫྎ⿬Ὑ᥀((2016/88/311 ᧜ᙳ)), c) ▼ᒣᶫୗὶᇦ((2016/9/1 ᧜ᙳ㸧86

2-1ୖὶഃࡢࡢ⅏ᐖ࣭࣭⿕⅏≧≧ἣᅗ ࡟㸪ୖὶഃࡢ⿕⅏༊㛫㸦ィ⏬໙㓄㸸1/48㸧ࡢ≧ἣࢆ♧ࡍ㸬⌧ᆅㄪᰝࡢ⤖ᯝ㸪◁㜵ࢲ࣒ୗὶࡢὶ㊰ᕤ༊㛫࡛ࡣṤ࡝ὶ㊰ኚືࡣㄆࡵࡽࢀ࡞࠿ࡗࡓࡀ㸪ὶ㊰ᕤ༊㛫ࡢ⤊஢ᆅⅬ࡟఩⨨ࡍࡿ⏫
㐨࣌ࢣࣞ࣋ࢶᕝᶫୗὶ࠿ࡽࡣ኱つᶍ࡞Ἑᗋపୗ࡜Ἑᓊᾐ㣗ࡀ☜ㄆࡉࢀࡓ㸬ࡲࡓ㸪UAV ᧜ᙳ㸦ᅗF㸧ࡼࡾ㸪⺬⾜㒊࡟࡚ὶ㊰ࡀ┤㐍ࡍࡿ࡜ඹ࡟㸪Ἑ㐨඲㠃࡟Ώࡗ࡚ᩘ࣓࣮ࢺࣝ࡟ཬࡪἙᗋపୗࡀ⏕ࡌࡓࡇ࡜ࡀ☜ㄆࡉࢀࡓ㸬ࡇࡢἙᗋపୗ࡟క࠸㸪ୖὶഃࡢ⿕⅏༊㛫࡛ࡣ㸪ᇙἐࡋ࡚࠸ࡓᮍᅛ⤖ࡢᇶᒾ࡛࠶ࡿ῰ᒣᒙࡀ኱つᶍ࡟㟢ฟࡋࡓ㸦ᅗF㸧㸬῰ᒣᒙࡀ㟢ฟࡋࡓሙ࡛ࡣἙᗋ࠿ࡽࡢᅵ◁౪⤥㔞ࡀῶᑡࡍࡿࡓࡵ㸪ฟỈ୰㸪ᶓ᪉ྥ࠿ࡽࡢᅵ◁ὶධࡀቑ࠼ࡸࡍࡃᕝᖜ඲㠃࡟Ώࡗ࡚Ἑᗋపୗࡀ㐍⾜ࡋࡸࡍ࠸≧ἣࡀ⏕ࡌࡿ࡜ඹ࡟㸪ฟỈᚋ༙࡟ࡣὶࢀࡀ㞟୰ࡍࡿࡓࡵ㸪῰ᒣᒙࡢ⦪ᾐ㣗ࡀ㐍ࢇࡔ࡜᥎ᐹࡉࢀࡿ㸬࡞࠾㸪⌧ᆅㄪᰝࡼࡾ㸪ࡉࡽ࡟ୖὶ࡟఩⨨ࡍࡿ◁㜵ࢲ࣒ࡣ‶◁࡟࡞ࡿࡲ࡛ᅵ◁ࢆᤕᤊࡋࡓࡇ࡜ࢆ☜ㄆࡋ࡚࠸ࡿ㸬1 ᇶ┠ࡢ◁㜵ࢲ࣒࡟ࡣ኱♟㸪2 ᇶ┠ࡢ◁㜵ࢲ࣒࡟ࡣከ㔞ࡢ⣽⢏ᅵ◁ࡀሁ✚ࡋ࡚࠸ࡓࡇ࡜࠿ࡽ㸪ฟỈ᫬㸪ୖὶࡢ◁㜵༊㛫࠿ࡽࡢᅵ◁౪⤥ࡣ㝈ࡽࢀ࡚࠸ࡓ࡜᥎ᐹࡉࢀࡿ㸬
2-2ୗὶഃࡢࡢ⅏ᐖ࣭࣭⿕⅏≧≧ἣᅗ ࠾ࡼࡧᅗ ࡟㸪ୗὶഃࡢ⿕⅏༊㛫㸦ィ⏬໙㓄㸸1/66㸧ࡢ≧ἣࢆ♧ࡍ㸬ୗὶഃࡢ⿕⅏༊㛫࡛ࡣ㸪ୖὶഃ࡜␗࡞ࡾ㸪ὶ㊰ࡀ኱ࡁࡃ⺬⾜ࡍࡿࡇ࡜࡛ᕥྑᓊࡢ㐃⥆ⓗ࡞ἙᓊḞቯࡀ⏕ࡌࡓ㸬ࡇࡢὶ㊰ࡢ⺬⾜໬࡟ࡼࡾ㸪▼ᒣᶫ㸪࣌ࢣࣞ࣋ࢶᶫ㸪᪂Ύᶫ㸪࠾ࡼࡧ᪂㘊ᶫ㸪࠸ࡎࢀࡶᶫྎ⿬ࡢᅵ◁ࡀὙ᥀ࡉࢀ㸪ࡑࢀ࡟క࠸ᶫྎ⿬ࡢ㐨㊰ࡢᔂⴠ➼ࡀ⏕ࡌࡓ㸬
2-3ᅵ◁ࡢሁሁ✚࡜࡜ᾐ㣗ᅗ ࡟㸪ୖὶഃ࠾ࡼࡧୗὶഃࡢ⿕⅏༊㛫࡟࠾ࡅࡿ᭱῝Ἑᗋࡢ⦪᩿ᅗࢆ♧ࡍ㸬ᅗ୰ࡢ㟷ࣛ࢖ࣥࡣ㸪1990 ᖺ௦ࡢἙᕝᩚഛ᫬ࡢィ⏬Ἑᗋ㧗࡛࠶ࡿ㸬ᅗ ࡼࡾ㸪ୖὶഃࡢ⿕⅏༊㛫࡛ࡣ᭱኱ 5m ⛬ᗘࡢἙᗋపୗࡀ⏕ࡌࡓࡇ࡜ࡀศ࠿ࡿ㸬ᅗ ࡟㸪Ἑ㐨ෆ࡛ࡢᅵ◁ࡢᾐ㣗㔞࡜ሁ✚㔞㸦ᅗD㸧㸪࠾ࡼࡧἙᓊࡢᾐ㣗㔞࡜ሁ✚㔞㸦ᚋ㏥࡜๓㐍㸧ࡢᴫ⟬್㸦ᅗE㸧ࢆ♧ࡍ㸬ࡇࢀࡣ㸪ᮏฟỈ๓㸦1990 ᖺ௦ࡢἙᕝᩚഛ᫬㸧ࡢ 㔞ᶓ᩿࡜ฟỈᚋࡢ 㔞ᶓ᩿㸦2016 ᖺ 9 ᭶ 㔞㸧ࡢᕪศࢆྲྀࡿࡇ࡜࡛ồࡵࡓᴫ⟬್࡛࠶ࡾ㸪ሁ✚࣭ᾐ㣗㔞ࢆ㐣኱ホ౯ࡋ࡚࠸ࡿྍ⬟ᛶ࡟ࡣὀពࡍࡿᚲせࡀ࠶ࡿࡶࡢࡢ㸪ᴫࡡࡢഴྥࢆㄞࡳྲྀࡿࡇ࡜ࡀ࡛ࡁࡿ㸬ᅗD ࡼࡾἙ㐨ෆࡢᾐ㣗㔞࡜ሁ✚㔞ࢆẚ㍑ࡍࡿ࡜㸪ୖὶഃ࡛ࡣἙ㐨ෆࡢᾐ㣗㔞ࡀ༟㉺ࡋࡓࡇ࡜㸪ୗὶഃ࡛ࡣἙ㐨ෆࡢሁ✚㔞ࡀ༟㉺ࡋࡓࡇ࡜ࡀศ࠿ࡿ㸬ࡲࡓ㸪ᅗE ࡼࡾἙᓊࡢᚋ㏥࡜๓㐍ഴྥࢆẚ㍑ࡍࡿ࡜㸪ୖὶഃ࡛ࡣྑᓊഃ࡟Ἑᓊᾐ㣗ࡀ༟㉺ࡋࡓࡇ࡜㸪ୗὶഃ࡛ࡣᕥྑᓊ஺஫࡟Ἑᓊᾐ㣗ࡀ⏕ࡌࡓࡇ࡜ࡀศ࠿ࡿ㸬ࡉࡽ࡟㸪ࡑࡢᾐ㣗㔞ࡣୗὶ࡬㐍ࡴ࡯࡝ቑຍࡋ࡚࠾ࡾ㸪ὶ㊰ࡢᶓ᪉ྥ࡬ࡢ⛣ື㔞ࡀḟ➨࡟኱ࡁࡃ࡞ࡗࡓᵝᏊࡀぢ࡚ྲྀࢀࡿ㸬ࡓࡔࡋ㸪඲యⓗ࡞ᅵ◁ࡢᾐ㣗㔞࡜ሁ✚㔞ࡢ཰ᨭࢆẚ㍑ࡍࡿ࡜㸪ᾐ㣗㔞࡟ᑐࡋ࡚ሁ✚㔞ࡀ᫂ࡽ࠿࡟ᑡ࡞࠸㸬ࡇࢀࡣ㸪⏕⏘ࡉࢀࡓᅵ◁ࡢከࡃࡀᮍᅛ⤖ᒾᒙ࡟⏤᮶ࡍࡿ⣽⢏ศ࡛࠶ࡗࡓࡓࡵ㸪ฟỈᚋ༙࡟࡞ࡿ࡯࡝ୖὶᇦ࡛⏕⏘ࡉࢀࡓᅵ◁ࡢ኱༙ࡀἙ㐨ෆ࡟ሁ✚ࡏࡎ㸪ୗὶࡢబᖠᕝࡲ࡛ὶࢀ㎸ࢇࡔࡓࡵ࡛ࡣ࡞࠸࠿࡜᥎ᐹࡉࢀ
ࡿ㸬

3㸬ᩘ್ゎᯒ
࣌ࢣࣞ࣋ࢶᕝ࡟࠾ࡅࡿฟỈ᫬ࡢὶ㊰ኚື≉ᛶ࠾ࡼࡧ⅏ᐖ࣭⿕⅏≧ἣࡢศᯒࢆ┠ⓗ࡟㸪ᖹ㠃 2ḟඖἙᗋኚືゎᯒࢆᐇ᪋ࡋࡓ㸬ゎᯒ࡟ࡣ iRIC Nays2DH 4) ࡟ᇙἐᇶᒾࡢ㧗ࡉࢆᶓ᩿ ⥺ࡈ࡜࡟87タᐃ࡛ࡁࡿࡼ࠺࡟ಟṇࢆຍ࠼ࡓࡶࡢࢆ⏝࠸ࡓ㸬ᅛᐃᗋ࡜⛣ືᗋࡢΰᅾሙࡢὶ◁㔞ࡢ᥎ᐃ࠾ࡼࡧἙᗋኚືィ⟬࡟ࡣᤲὶ◁ᒙࣔࢹࣝࢆ⏝࠸࡚࠸ࡿ 2), 3)㸬

ᅗ-5 ⦪᩿ᅗᅗᅵᅵ◁ࡢὶฟ㔞࡜ሁ✚㔞((ᴫ⟬್)) a) Ἑ㐨ෆࡢᾐ㣗࣭࣭ሁ✚㔞㸪bb) Ἑᓊࡢࡢᾐ㣗࣭࣭ሁ✚㔞ィ⟬㡿ᇦࡣ㸪⏫㐨࣌ࢣࣞ࣋ࢶᕝᶫ࠿ࡽᕷ⾤ᆅ௜㏆ࡢ᪂Ύᶫୗὶᇦࡲ࡛ࢆタᐃࡋࡓ㸬ୖὶ➃ὶ㔞ࡣ㸪࣌ࢣࣞ࣋ࢶᕝࡢỈ఩࣭ὶ㔞ほ ್ࡀฟỈ୰࡟Ḟ ࡋࡓࡓࡵ㸪ᅗ ࡟♧ࡍศᕸᆺὶฟࣔࢹࣝࢆ⏝࠸࡚᥎ᐃࡉࢀࡓࡶࡢࢆ౑⏝ࡋࡓ 4㸧㸬࡞࠾㸪ᮏ್ࡣ໭ᾏ㐨᥎ᐃࡢὶ㔞㸦⣙ 400m3/sec㸧ࡼࡾࡶࣆ࣮ࢡ್㸦⣙ 250m3/sec㸧ࡀᑠࡉ࠸್࡜࡞ࡗ࡚࠸ࡿࡀ㸪୰ᑠἙᕝࡢὶ㔞ࣆ࣮ࢡࡢୖ᪼㏿ᗘࡀ୙᫂ࡢࡓࡵ㸪ࡇࡇ࡛ࡣ㝆㞵᝟ሗ࠿ࡽᚓࡽࢀࡓ᥎⟬ࣁ࢖ࢻࣟࢢࣛࣇࢆࡑࡢࡲࡲ⏝࠸ࡓ㸬Ἑᗋᮦᩱࡣ⌧ᆅㄪᰝ⤖ᯝ㸦໭ᾏ㐨ᥦ౪㸧ࡼࡾ 90mm ࡢᆒ୍⢏ᚄ࡜ࡋ㸪࣐ࢽࣥࢢ⢒ᗘಀᩘࡣ 0.030 ୍࡛ᐃ್ࢆ୚࠼ࡓ㸬88ᅗゎ
ゎᯒ࡟⏝࠸ࡓࣁ
ࣁ࢖ࢻࣟࢢࣛࣇ

ᅗC
Case1 ࡢỈ῝ࢥࣥࢱ࣮ᅗ㸦ὶࢀࡢࡳࡢィ⟬ᅗ Case 2 ࡢἙᗋኚືࢥࣥࢱ࣮ᅗ89ゎᯒࡣ 4 ࢣ࣮ࢫ࡜ࡋ㸪ὶࢀࡢィ⟬ࡢࡳᑐ㇟࡜ࡋࡓ Case 1 ࡜ᅵ◁ࡢ⛣ືࢆ⪃៖ࡋࡓ Case 2 ~Case 4 ࢆᐇ᪋ࡋࡓ㸬Case 2 ࡣᮏฟỈࡢ෌⌧ィ⟬࡛࠶ࡿ㸬ᮏィ⟬࡛ࡣ㸪⌧ᆅㄪᰝࡼࡾ◁㜵ࢲ࣒ࡢᅵ◁ᤕᤊຠᯝࡀ኱ࡁ࠿ࡗࡓ࡜᥎ᐹࡉࢀࡓࡇ࡜࠿ࡽ㸪ୖὶ➃࠿ࡽࡢᅵ◁౪⤥㔞ࢆᖹ⾮ὶ◁㔞ࡢ
50%࡜௬ᐃࡋ㸪ᇙἐࡍࡿᇶᒾࡀ㟢ฟࡍࡿ᮲௳࡜ࡋ࡚࠸ࡿ㸬ᇶᒾࡢᇙἐ῝ࡣ㸪㐣ཤࡢ࣮࣎ࣜࣥࢢㄪᰝ⤖ᯝ㸦໭ᾏ㐨ᥦ౪㸧ࢆཧ⪃࡟㸪ィ⟬᱁Ꮚࡢᶓ᩿ ⥺ࡈ࡜࡟᭱῝Ἑᗋࡼࡾ 30cm ῝࠸ሙᡤ࡟タᐃࡋ࡚࠸ࡿ㸬Ἑᗋኚືィ⟬࡛ࡣ㸪㞄ࡾྜ࠺࣓ࢵࢩࣗ㛫ࡢἙᗋ㧗ࡢᕪࡀᏳᜥゅ௨ୗ࡟࡞ࡿࡼ࠺࡟ࡋ࡚࠸ࡿ㸬㟢ฟࡋࡓᇶᒾࡢᾐ㣗ࡣ㸪࣌ࢣࣞ࣋ࢶᕝࡢᮍᅛ⤖ᒾࡢᛶ㉁ࡀ୙࡛᫂࠶ࡿࡇ࡜㸪ฟỈ୰ࡢୖὶ➃࠿ࡽࡢᅵ◁౪⤥㔞ࡀ௬ᐃ್࡛࠶ࡿࡇ࡜㸪ฟỈࡀẚ㍑ⓗ▷᫬㛫࡛࠶ࡗࡓࡇ࡜➼࠿ࡽ㸪㠀ᾐ㣗ᛶࡢᇶᒾ࡜ࡋ࡚ᢅࡗ࡚࠸ࡿ㸬Case 3 ࡣ㸪ᇙἐᇶᒾࡀᏑᅾࡋ࡞࠸ሙྜ࡛࠶ࡾ㸪Case 2 ࡜ὶ㊰ኚື≉ᛶࢆẚ㍑ࡍࡿࡶࡢ࡛࠶ࡿ㸬Case 4 ࡣ㸪ୖὶ➃࠿ࡽࡢᅵ◁౪⤥㔞ࡀ༑ศᏑᅾࡍࡿ㸦ᖹ⾮ὶ◁㔞㸧ሙྜ࡛࠶ࡾ㸪Case 2 ࡜ὶ㊰ኚື≉ᛶࢆẚ㍑ࡍࡿࡶࡢ࡛࠶ࡿ㸬4. ᩘ್ゎᯒࡢࡢ⤖ᯝ࡜⪃ᐹ
4-1 ὶࢀࡢࡳࡢィ⟬㸦CCase 1㸧
ᅗ ࡟㸪Case 1 ࡢὶ㔞ࣆ࣮ࢡ᫬࡟࠾ࡅࡿỈ῝ࢥࣥࢱ࣮ᅗࢆ♧ࡍ㸬ᅗ ࡼࡾ㸪ᅵ◁ࡢ⛣ືࢆ⪃៖ࡋ࡞࠸ሙྜ㸪࣌ࢣࣞ࣋ࢶᕝࡢᕷ⾤ᆅ௜㏆ࡢᾐỈ⠊ᅖࡣẚ㍑ⓗᑠࡉ࠸ࡇ࡜ࡀศ࠿ࡿ㸬ࡘࡲࡾ㸪௒ᅇࡢ࣌ࢣࣞ࣋ࢶᕝ࡟࠾ࡅࡿ⅏ᐖ࣭⿕⅏ࡣ㸪ィ⏬つᶍ௨ୖࡢὶ㔞࡟క࠺኱㔞ࡢᅵ◁ࡢ⛣ື࡟ࡼࡾ㸪Ἑ㐨ࡀእຊ࡟⪏࠼ࡽࢀࡎ㸪኱つᶍ࡟ᕝᖜࡀᣑᖜࡋ㸪ὶ㊰ኚືࡀ⏕ࡌࡓࡇ࡜ࡀせᅉࡔ࡜᥎ᐹࡉࢀࡿ㸬
4-2 ෌⌧ィ⟬㸦CCase 2㸧ᅗ ࡟ Case 2 ࡢἙᗋ࣭ὶ㊰ኚືࡢ᫬㛫ኚ໬ࡢᵝᏊࢆ㸪ᅗ ࡟ᅗH ࡟♧ࡍ SP4650 m ࡜SP4400 m ᆅⅬ௜㏆࡟࠾ࡅࡿᶓ᩿ 㔞ࢹ࣮ࢱࢆ♧ࡍ㸬ᅗ ࡼࡾ㸪ᮏィ⟬࡛ࡣᮍᅛ⤖ᒾࡢὙ᥀⌧㇟ࡲ࡛ࡣ⪃៖ࡋ࡞࠿ࡗࡓࡶࡢࡢ㸪ୖὶഃࡢ⿕⅏༊㛫࡟࠾࠸࡚ᅗ ࡟♧ࡍࡼ࠺࡟Ἑ㐨඲㠃࡟ࢃࡓࡗ࡚኱つᶍ࡟Ἑᗋపୗࡍࡿࡇ࡜ࡸ㸪ᅗ ࡢ SP4400 m ᆅⅬ௜㏆ࡢ⺬⾜㒊࡟࡚ὶ㊰ࡀྑᓊ࠿ࡽᕥᓊഃ࡟ษࡾ᭰ࢃࡿࡇ࡜➼ࡀ෌⌧࡛ࡁ࡚࠾ࡾ㸪ࡇࡇ࡛ࡢὶ㊰ኚື≉ᛶࡢ⪃ᐹ࡟࠶ࡿ⛬ᗘ༑ศ࡞⢭ᗘࡀ࠶ࡿ࡜⪃࠼ࡽࢀࡿ㸬ḟ࠸࡛㸪ᅗD㹼ᅗH ࡼࡾἙᗋ࣭ὶ㊰ኚືࡢ᫬㛫ኚ໬ࢆ☜ㄆࡍࡿ㸬ᅗD ࠾ࡼࡧᅗE
ࡼࡾ㸪ୖὶഃࡢ⿕⅏༊㛫࡛ࡣ㸪ὶ㔞ࡀ 180m3/s ⛬ᗘ࡟㐩ࡍࡿ㡭ࢆቃ࡟⌧㇟ࡀኚ໬ࡍࡿ≧ἣࡀ♧ࡉࢀࡓ㸬⺬⾜㒊ᾘኻ௨๓࡟ࡣ᫂░࡞Ἑᗋపୗࡣㄆࡵࡽࢀ࡞࠿ࡗࡓ㸦ᅗD㸧ࡀ㸪ὶ㔞 180m3/s ⛬ᗘ࡟㐩ࡍࡿ࡜⺬⾜㒊࡛ࡣὶ㊰ࢆ⥔ᣢ࡛ࡁࡎ㸪ὶ㊰ࡣษࡾ᭰ࢃࡾ㸦Chute cutoff㸧㸪┤㐍ࡋࡓ㸦ᅗE㸧㸬ࡲࡓ㸪ࡇࡢ㡭࠿ࡽᇶᒾࡢ㟢ฟᇦࡶቑຍࡋࡓ㸬ࡉࡽ࡟ὶ㔞ࡀቑຍࡍࡿ࡜㸪ᅗF ࠾ࡼࡧᅗG ࠿ࡽศ࠿ࡿࡼ࠺࡟Ἑ㐨඲㠃࡟ࢃࡓࡗ࡚ⴭࡋ࠸Ἑᗋపୗࡀ⏕ࡌࡓ㸬㸪୍᪉㸪ୗὶഃࡢ⿕⅏༊㛫࡛ࡣ㸪ὶ㔞ࡀ 200m3/s ⛬ᗘ࡟㐩ࡍࡿ㡭࠿ࡽὶ㊰ࡀ⺬⾜໬ࡋ㸦ᅗF㸧ᕥྑᓊ஺஫ࡢἙᓊḞቯࢆࡶࡓࡽࡋࡓ㸬ࡇࢀࡣ㸪໙㓄ࡢⱝᖸࡺࡿ࠸ୗὶ༊㛫࡛ࡣἙ㐨ෆ࡟኱㔞࡟ᅵ◁ࡀሁ✚ࡋ㸪ࡑࢀ࡟ࡼࡗ࡚ὶ㊰ࡢ⺬⾜໬ࡀಁࡉࢀࡓࡓࡵ࡜⪃࠼ࡽࢀࡿ㸬ࡲࡓ㸪ᩘ್ゎᯒ࡟ࡼࡿ࡜㸪ὶ㊰ࡢ⺬⾜ࡣὶ㔞ቑຍ࡟క࠸ୗὶഃ࡬࡜ఏ᧛㸦ᅗG㸧ࡍࡿࡢࡳ࡛࡞ࡃ㸪ὶ㔞పୗ᫬࡟࠾࠸࡚ࡶὶ㊰ᶓ᪉ྥ࡬࡜Ⓨ㐩ࡍࡿᵝᏊࡀ☜ㄆࡉࢀࡓ㸦ᅗH㸧㸬
4-3 ᇙἐᇶᒾࡀᏑᅾࡋ࡞࠿ࡗࡓሙྜ㸦CCase 3㸧ᅗ ࡟㸪Case 2 ࡜ Case 3 ࡢィ⟬⤊஢᫬࡟࠾ࡅࡿἙᗋኚື㔞࡜㸪ὶ㔞ࣆ࣮ࢡ᫬ࡢὶ㏿ࡢࢥࣥ90ࢱ࣮ᅗࢆ♧ࡍ㸬ᅗ ࡼࡾ㸪Case 2 ࡜ Case 3 ࡢἙᗋኚື㔞ࢆẚ㍑ࡍࡿ࡜㸪ᇙἐᇶᒾࡢᏑᅾࡢ᭷
↓࡟ࡼࡗ࡚ୖὶഃࡢ⿕⅏༊㛫࡟࠾ࡅࡿἙᗋపୗ㔞ࡀ኱ࡁࡃ␗࡞ࡿࡇ࡜ࡀ♧ࡉࢀࡓ㸬୍᪉㸪ୗὶഃࡢ⿕⅏༊㛫࡛ࡣୖὶഃ࡟࡚ᇶᒾࡀ㟢ฟࡋ㸪ὶ◁㔞ࡀḟ➨࡟ῶ⾶ࡋࡓࡇ࡜࡟ࡼࡿᙳ㡪ࢆ࡯࡜ࢇ࡝ཷࡅ࡞࠿ࡗࡓࡇ࡜ࡀศ࠿ࡿ㸬ᅗ⌧ᆅᶓᶓ᩿㔞ࢹ࣮ࢱ

ᅗ Case 2 ࡢἙᗋኚືࢥࣥࢱ࣮ᅗ
ᅗ ィ⟬⤖ᯝ㸸ᶓ᩿ᅗ

91ᅗ ࡟㸪ᅗH ࡟♧ࡍ SP4650 m ࡜ SP4400 m ᆅⅬࡢ⥺௜㏆ࡢィ⟬⤊஢᫬ࡢᶓ᩿ᅗ㸪ᅗ࡟ฟỈࣆ࣮ࢡ᫬ࡢᤲὶ◁㔞ࡢ⦪᩿ศᕸࢆ♧ࡍ㸬ᅗ ࡼࡾ㸪ᇶᒾࡢᇙἐࢆ⪃៖ࡋ࡞࠸ Case 3 ࡛ࡣ㸪Case 2 ࡸ⌧ᆅㄪᰝ࡛☜ㄆࡉࢀࡓἙ㐨඲య࡟࠾ࡼࡪᇶᒾࡢᇙἐࡍࡿ῝ࡉࡲ࡛ࡢ኱つᶍ࡞Ἑᗋపୗࡀㄆࡵࡽࢀ࡞࠸ࡇ࡜ࡀศ࠿ࡿ㸬ࡇࢀࡣ㸪ᅗ ࠿ࡽศ࠿ࡿࡼ࠺࡟㸪ᇶᒾࡀ㟢ฟࡍࡿࡇ࡜࡛ୖὶഃ࠿ࡽᤲὶ◁㔞ࡀḟ➨࡟ῶ⾶ࡋࡓࡓࡵ㸪ࡑࡢୗὶᇦ࡟࠾࠸࡚ࡶ᪂ࡓ࡟ᇶᒾࡀ㟢ฟࡋࡸࡍ࠸≧ἣࡀ⏕ࡌ㸪ࡑࡢᇶᒾ㟢ฟ࡟క࠸Ἑᗋ࠿ࡽࡢᅵ◁౪⤥ࡀ࡞ࡃ࡞ࡿࡇ࡜࡛ὶ㊰ᶓ᪉ྥ࠿ࡽࡢᅵ◁౪⤥ࡀቑຍࡋࡸࡍ࠸≧ἣࡀ⏕ࡌࡓࡓࡵ࡜᥎ᐹࡉࢀࡿ㸬ᇶᒾࡀ୍ᗘ㟢ฟࡍࡿ࡜୙ྍ㏫ⓗ࡟ᇶᒾ㟢ฟᇦࡢᣑ኱ࡀ㐍⾜ࡋࡸࡍ࠸ࡓࡵ㸪௒ᚋ㸪࡝ࡢࡼ࠺࡟ᩚഛࢆ㐍ࡵࡿ࠿ࡣ኱ࡁ࡞ㄢ㢟࡟࡞ࡿࡶࡢ࡜⪃࠼ࡽࢀࡿ㸬࡞࠾㸪ᅗ ࡢὶ㏿ࢥࣥࢱ࣮ᅗ࡟ࡼࡿ࡜㸪ᇶᒾࡀ㟢ฟࡋ࡞࠸ሙྜ㸪ୖὶഃࡢ⿕⅏༊㛫࡟ࡣඖࡢ⺬⾜㒊ࡼࡾࡶἼ㛗ࡢ㛗࠸⺬⾜ὶ㊰ࡀ᪂ࡓ࡟ᙧᡂࡉࢀࡿࡼ࠺࡛࠶ࡿ㸬ḟ࡟㸪ୗὶഃࡢ⿕⅏༊㛫࡟ࡘ࠸࡚⪃ᐹࡍࡿ㸬ᅗ ࡼࡾ Case 2 ࡜ Case 3 ࢆẚ㍑ࡍࡿ࡜㸪࠸ࡎࢀࡶୖὶഃ࡜ୗὶഃࡢ⿕⅏༊㛫ࡢ㛫࡟࠶ࡿ໙㓄ኚ໬Ⅼࡼࡾᗄศୖὶഃ࠿ࡽᅵ◁ࡀሁ✚ࡋ࡚࠸ࡿࡇ࡜ࡀศ࠿ࡿ㸬ࡲࡓ㸪ᅗ ࡼࡾ㸪ࡇࢀࡼࡾୗὶᇦ࡛ࡣᇶᒾ㟢ฟ࡟క࠺ᤲὶ◁㔞ࡢῶ⾶ࡀ⏕ࡌ࡚࠸࡞࠸ࡇ࡜ࡀศ࠿ࡿ㸬ࡇࡢࡇ࡜࠿ࡽ㸪ୖὶഃ࡜ୗὶഃࡢ⿕⅏༊㛫ࡢ㛫࡟ẚ㍑ⓗከ㔞࡟ᅵ◁ࡀሁ✚ࡋࡸࡍ࠸ሙࡀᏑᅾࡋࡓࡇ࡜࡛㸪ࡇࡢሙᡤ࡟࠾࠸࡚ୖὶ࠿ࡽ㐍⾜ࡋ࡚ࡁࡓᇶᒾ㟢ฟࡀṆࡲࡗࡓ࡜⪃࠼ࡽࢀࡿ㸬࡞ࡽࡧ࡟㸪ᅵ◁ࡢሁ✚࡟ࡼࡾୗὶ࡬ࡢᅵ◁౪⤥㔞ࡀ࡯ࡰỈ⌮㔞࡟ᛂࡌࡓᖹ
⾮ᤲὶ◁㔞࡜࡞ࡗࡓࡓࡵ㸪Case 2 ࡜ Case 3 ࡛㢮ఝࡋࡓὶ㊰ኚືࡀᚓࡽࢀࡓ࡜⪃࠼ࡽࢀࡿ㸬࡞࠾㸪Case 2 ࡢୗὶᇦ࡟࡚ᤲὶ◁㔞ࡀⱝᖸῶᑡࡍࡿࡢࡣ㸪Ἑᓊ௜㏆ࡢᒁᡤὙ᥀࡟ࡼࡗ࡚ᇶᒾࡀ㟢ฟࡋࡓࡓࡵ࡛࠶ࡿ㸬⌧ᆅㄪᰝ࡛ࡣᕷ⾤ᆅ௜㏆ࡢὙ᥀⟠ᡤࡢ≧ἣࡣᢕᥱ࡛ࡁ࡞࠿ࡗࡓࡓࡵ㸪ࡇࡇ࡛ᇶᒾࡀ෌ࡧ㟢ฟࡋࡓ࠿࡝࠺࠿࡟ࡘ࠸࡚ࡣ୙࡛᫂࠶ࡿ㸬4-4 ୖὶ࠿ࡽ༑ศ࡞ᅵ◁౪⤥ࡀᏑᅾࡋࡓሙྜ㸦CCase 4㸧
ᅗ-14 ࡟㸪Case 2 ࡜ୖὶ࠿ࡽࡢᅵ◁౪⤥㔞ࡀ༑ศᏑᅾࡋࡓ Case 4 ࡢィ⟬⤊஢᫬ࡢἙᗋኚື㔞ࡢࢥࣥࢱ࣮ᅗࢆ♧ࡍ㸬ᅗ-14 ࡼࡾ㸪ୖὶ➃࠿ࡽ༑ศ࡞ᅵ◁౪⤥ࡀ࠶ࡿ Case 4 ࡛ࡣ㸪Case 2 ࡜␗࡞ࡾ㸪ୖὶഃࡢ⿕⅏༊㛫࡟࠾࠸࡚ὶ㊰ࡀἙᗋపୗࡏࡎ㸪ᇙἐᇶᒾࡢ኱つᶍ࡞㟢ฟࡶ⏕ࡌ࡞࠸ࡇ࡜ࡀศ࠿ࡿ㸬ࡇࡢࡇ࡜࠿ࡽ㸪ୖὶഃࡢ⿕⅏༊㛫࡛ࡣ㸪௒ᅇ᝿ᐃ௨ୖࡢὶ㔞ࡀὶࢀࡓ࠺࠼㸪ࡉࡽ࡟ୖὶ࠿ࡽࡢᅵ◁౪⤥ࡀᑡ࡞࠿ࡗࡓࡓࡵ㸪ᇶᒾࡀ㟢ฟࡍࡿࡲ࡛Ἑᗋపୗࡀ⏕ࡌࡓ࡜⪃࠼ࡽࢀࡿ㸬୍᪉㸪ୗὶഃࡢ⿕⅏༊㛫ࢆẚ㍑ࡍࡿ࡜㸪Case 2 ࡜ Case 4 ࡛ࡣୖὶഃࡢ⿕⅏༊㛫࡟࠾ࡅࡿὶ㊰ኚືࡀ࠿࡞ࡾ␗࡞ࡿ࡟ࡶ㛵ࢃࡽࡎ㸪ୗὶഃ࡛ࡣ㢮ఝࡍࡿὶ㊰ኚືࡀ⏕ࡌࡿࡇ࡜ࡀศ࠿ࡿ㸬ࡘࡲࡾ㸪௒ᅇࡢฟỈ࡛ࡣୖὶ➃࠿ࡽࡢᅵ◁ὶධ㔞ࡸୖὶഃࡢ⿕⅏༊㛫࡟࠾ࡅࡿὶ㊰ኚືࡢ≧ἣࡀୗὶഃࡢὶ㊰ኚື࡟Ṥ࡝ᙳ㡪ࢆ୚࠼࡞࠿ࡗࡓྍ⬟ᛶࡀ♧ࡉࢀࡓ㸬௨ୖࡢ᳨ウࡼࡾ㸪௒ᅇࡢ࣌ࢣࣞ࣋ࢶᕝࡢฟỈ࡛ࡣ㸪ୖὶഃ࡛ࡢᅵ◁ᢚไᑐ⟇ࡢࡳ࡛ୗὶഃࡢὶ㊰ኚືࢆᢚไࡍࡿࡇ࡜ࡣ㞴ࡋ࠿ࡗࡓࡶࡢ࡜᥎ᐹࡉࢀࡿ㸬୍㐃ࡢィ⟬⤖ᯝ࠿ࡽࡶ♧ࡉࢀࡿࡼ࠺࡟㸪ᮏฟỈ࡛ࡣィ⏬つᶍ௨ୖࡢὶ㔞࡟క࠸኱㔞ࡢᅵ◁ࡀ⛣ືࡋࡓࡇ࡜࡟ࡼࡗ࡚㸪እຊ࡟⪏࠼ࡽࢀࡎἙ㐨ࡀᣑᖜࡋࡓ㸬ࡲࡓ㸪Ἑ㐨ࡀᣑᖜࡍࡿ㝿࡟⺬⾜ࡀ኱ࡁࡃቑᖜࡋ࡚࠾ࡾ㸪ࡇࡢὶ㊰ኚືࡢᛶ㉁ࡀ⿕ᐖࢆ኱ࡁࡃࡋࡓ࡜᥎ᐹࡉࢀࡿ㸬௒ᚋ㸪ࡇࡢࡼ࠺࡞ᅵ◁ࡢ⛣ື࡜ὶ㊰ኚືࡢᛶ㉁ࢆ㋃ࡲ࠼ࡓୖ࡛㸪ᅵ◁⛣ືࢆᢚไࡍࡿᑐ⟇࡟ຍ࠼࡚㸪Ἑᓊࡢㆤᓊࢆᙉ໬ࡍࡿ࡞࡝㸪Ἑ㐨ࡢᏳᐃᛶࢆ㧗ࡵ࡚ὶ㊰ࡢἙᗋపୗ࠾ࡼࡧᶓ᪉ྥ࡬ࡢ⛣ືࢆᢚṆࡍࡿࡼ࠺࡞ᑐ⟇ࡀᮃࡲࢀࡿ㸬92ᅗィィ⟬⤖ᯝ㸸ᤲὶ◁㔞ࡢ⦪᩿ኚ໬

ᅗCase 2 ࡜ Case 4 ࡢィ⟬⤊஢᫬ࡢἙᗋኚື㔞ࢥࣥࢱ࣮ᅗ5㸬⤖ㄽ
2016ᖺ8᭶㸪໭ᾏ㐨࡟㐃⥆ࡋ࡚฿᮶ࡋࡓ4ࡘࡢྎ㢼࡟ࡼࡾ㸪ᖏᗈᆅ༊ࢆὶࢀࡿ༑຾⟶ෆࡢከࡃࡢἙᕝ࡛ࡣィ⏬㧗Ỉࢆ㉸࠼ࡿ᪤ ᭱኱ὶ㔞ࢆほࡋࡓ㸬ᮏ◊✲࡛ࡣ᭱ࡶ⿕ᐖつᶍࡢ኱ࡁ࠿ࡗࡓΎỈ⏫ࢆὶࢀࡿ࣌ࢣࣞ࣋ࢶᕝࢆᑐ㇟࡟㸪⿕⅏≧ἣ࡜ὶ㊰ኚື≉ᛶࢆᢕᥱࡋࡓ㸬⌧ᆅㄪᰝࡢ⤖ᯝ㸪ୖὶഃࡢ⿕⅏༊㛫࡛ࡣ኱つᶍ࡟Ἑᗋࡀపୗࡋὶ㊰ࡀ┤⥺໬ࡋࡓ୍᪉࡛㸪ୗὶഃࡢ⿕⅏༊㛫࡛ࡣἙ㐨ෆ࡟ᅵ◁ࡀሁ✚ࡋ㸪ὶ㊰ࡀ⺬⾜໬ࡋ㸪ᕥྑᓊࡢ㐃⥆ⓗ࡞Ἑᓊᾐ㣗ࡀ⏕ࡌࡓࡇ࡜ࡀ☜ㄆࡉࢀࡓ㸬ᩘ್ゎᯒ࡟ࡼࡿ࡜㸪ୖὶഃࡢ⿕⅏༊㛫࡛ࡣᅵ◁౪⤥㔞ࡢ୙㊊࡟ࡼࡾᇶᒾࡀ㟢ฟࡋ㸪ࡑࡢᇶᒾ㟢ฟ࡟ࡼࡗ࡚኱つᶍ࡞Ἑᗋపୗࡀ⏕ࡌࡓࡇ࡜ࡀ♧ࡉࢀࡓ㸬୍᪉㸪ୗὶഃࡢ⿕⅏༊㛫࡛ࡣᅵ◁ࡢሁ✚࡟క࠸ୖὶ࠿ࡽ㐍⾜ࡋ࡚ࡁࡓἙᗋపୗࡀṆࡲࡗࡓࡶࡢࡢ㸪᝿ᐃ௨ୖࡢὶ㔞࡟క࠸኱㔞ࡢᅵ◁ࡀ⛣ືࡋࡓࡇ࡜࡟ࡼࡗ࡚Ἑ㐨ࡀᣑᖜࡋ㸪ὶ㊰ࡀ⺬⾜໬ࡋࡓ㸬௒ᚋ㸪ᅵ◁⛣ືࢆᢚไࡍࡿᑐ⟇࡟ຍ࠼࡚㸪Ἑᓊࡢㆤᓊࢆᙉ໬ࡍࡿ࡞࡝㸪ὶ㊰ࡢᶓ᪉ྥ࡬ࡢ⛣ືࢆᢚṆࡍࡿࡼ࠺࡞ᑐ⟇ࡀᮃࡲࢀࡿ㸬ཧ⪃ᩥ⊩(1) ໭ᾏ㐨㛤Ⓨᒁ㸸ᖹᡂ 28 ᖺ 8 ᭶ 20 ᪥࠿ࡽࡢ኱㞵ཬࡧྎ㢼➨ 10 ྕ࡟ࡼࡿฟỈࡢᴫせ, ໭ᾏ㐨㛤Ⓨᒁᘓタ㒊 Ἑᕝ⟶⌮ㄢỈ⅏ᐖணሗࢭࣥࢱ࣮, ᖹᡂ 28 ᖺ 9 ᭶ 29 ᪥.
(2) iRIC ࢯࣇࢺ࢙࢘࢔ http:/i-ric.org(3) L. X. Luu, S. Egashira, and H. Takebayashi: Investigation of Tan Chau Reach in lower
Mekong using field data and numerical simulation, Annual Journal of Hydraulic Engineering,
JSCE, 48, pp.1057-1061, 2004.
 ᑠụ㐩ஓ, ୰ὠᕝㄔ㸸2016 ᖺ 8 ᭶ࡢ㐃⥆ࡋࡓ኱㞵࡟క࠺ὥỈὶฟ㔞ࡢ෌⌧᳨ド, ᅵᮌᏛ఍໭ᾏ㐨ᨭ㒊, 73, 2017.

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