東北地域災害科学研究

127第55巻（2019）ᑠᕝཎ†ሷỈ㐳ୖ≉ᛶඵᡞᕤᴗ኱ᏛᕤᏛ㒊ᅵᮌᘓ⠏ᕤᏛ⛉ ᮌᮧ ⓚ௓࣭బࠎᮌ ᖿኵࠊ㕲ᘓᘓタओ ຌย ᬛ1.ࡣࡌࡵ࡟ᮏ◊✲࡛ࡣ㟷᳃┴ࡢᮾ㒊࡟఩⨨ࡍࡿᑠᕝཎ†ࢆㄪᰝᑐ㇟࡟ࡋ࡚࠸ࡿ(ᅗ 1)ࠋᑠᕝཎ†ࡣ†἟㠃✚ 62.12km2ࠊỈ㠃ࡢᶆ㧗ࡣ 2014 ᖺᖹᆒỈ఩ࡀ 0.291m ࡜࡞ࡗ࡚࠸ࡿࠋᑠᕝཎ†ࡣ᪥ᮏࡢ†἟࡛ࡣ 11 ␒┠ࡢ㠃✚つᶍࢆ᭷ࡋ࡚࠸ࡿ(ỶỈ†ࡢ࡞࠿࡛ࡣ 5 ␒┠)ࠋ㟷᳃┴࡛ࡣࠊ᭱኱
ࡢ†࡛࠶ࡿࠋࡲࡓࠊὶධἙᕝࡣ୐ᡞᕝࡸⰼษᕝ࡞࡝ 6 ୺せἙᕝ࡛ࠊὶฟἙᕝࡣ㧗℩ᕝ࡜࡞ࡗ࡚࠸ࡿࠋᑠᕝཎ†ࡢỈ㉁ࡀᖹᡂ 16 ᖺ࠿ࡽᖹᡂ 26 ᖺ࡟࠿ࡅ࡚ᛴ⃭࡟ᝏ໬ࡋ࡚࠸ࡿࠋỈ㉁ᝏ໬ࡢཎᅉ࡜ࡋ࡚㐍ධሷศ㔞ࡢቑຍࡸࠊሷῐቃ⏺
㠃ࡢୖ᪼ࡀ⪃࠼ࡽࢀ࡚࠸ࡿࠋࡋ࠿ࡋࠊ†࡬ࡢሷỈ㐍ධ࡟ࡘ࠸࡚ࡣ୙᫂࡞Ⅼࡀከࡃࠊゎ᫂ࡀᛴࡀࢀࡿࠋ
ࡑࡇ࡛ࠊᮏ◊✲࡛ࡣࠊ†ཱྀ࡟࠾ࡅࡿሷỈ㐳ୖ≉ᛶࢆ᫂ࡽ࠿࡟ࡍࡿࡇ࡜ࢆ◊✲ࡢ┠ⓗ࡜ࡋ࡚࠸ࡿࠋ௒ᖺᗘࡣࠊ†ཱྀ㒊ࠊ໭㒊†ᓊ㏆ࡃ࡟఩⨨ࡍࡿ⃢➽࡟࠾ࡅࡿ㐳ୖሷỈሢࡢᣲືࢆ⌧ᆅほᅗ 1 ᑠᕝཎ†఩⨨࡟ࡼࡾ᳨ウࡋ

࡚ࡳࡿࠋほ ࡣᖹᡂ 30 ᖺ 11 ᭶ 7 ᪥࠿ࡽ 12 ᭶ 10᪥ࡲ࡛ࡢ⣙ 1 ࣧ᭶㛫⾜ࡗࡓࠋ
2.ほほ᪉ἲ
ࡣ⮬グᘧࡢὶྥὶ㏿ィ㸦No㸬104㸧㸦෗┿ 1㸧ࠊᑠᕝཎ†⁺༠ࡼࡾ㈚୚ࢆཷࡅ࡚౑⏝ࡋࡓሷศỈ ィ㸦No.1060㸪No.1061㸧
㸦෗┿ 2㸧ࠊỈ ሷศィ㸦No.336㸪No.337㸧
㸦෗┿㸱㸧ࠊỈሷศィ㸦No.007㸧㸦෗┿㸲㸧ࢆ⏝࠸࡚ࠊ2018 ᖺ 11 ᭶ 7 ᪥࠿ࡽ 12 ᭶ 10 ᪥࡟࠿ࡅ࡚⾜ࡗࡓࠋ෗┿ 1 ὶྥὶ㏿ィ㸦No.104㸧෗┿㸯࡟♧ࡍὶྥ࣭ὶ㏿ィࢆᗏ㠃࠿ࡽ 0.8㹫ࡢ㧗ࡉ࡟タ⨨ࡋ ᐃࢆ⾜ࡗࡓࠋᗏ㠃㏆ࡃࡢὶືࢆ࡜ࡽ࠼ࡿࡓࡵ࡟ୗᒙࡢὶືࢆ ᐃࡍࡿࡇ࡜࡟㔜Ⅼࢆ⨨࠸ࡓタ⨨࡜࡞ࡗ࡚࠸ࡿࠋ෗┿ 2 ࡣᑠἙཎ†⁺༠⤌ྜࡢሷศィ࡛࠶ࡾࠊ⁺༠ࡢཌព࡟ࡼࡾࡇࡢሷศィࢆ೉ࡾ࡚ᐃࢆ⾜ࡗ࡚࠸*Characteristics of saltwater intrusion in Lake Ogawara by Kosuke Kimura, Mikio

Sasaki and Satoshi Kunugi

128ࡿࠋ෗┿㸱ࡣ᫖ᖺᗘ࡟᪂ࡓ࡟ᮏ◊✲ᐊ࡛㉎ධࡋࡓ᪂ࡋ࠸Ỉ ሷศィ࡛࠶ࡾࠊᗏ㠃࠿ࡽ 0.3㹫
࡜ 0.6㹫ࡢ㧗ࡉ࡟タ⨨పᒙࡢሷỈࡢືࡁࢆ࡜ࡽ࠼ࡿࡼ࠺࡟౑⏝ࡋ࡚࠸ࡿࠋ෗┿㸰 ౑⏝ࡋࡓᑠᕝཎ†⁺༠ࡢỈ ሷศィ㸦No.1060㸪1061㸧෗┿㸱 Ỉ ሷศィ㸦No.336㸪337㸧෗┿㸲 ࣡࢖ࣃ࣮௜ࡁỈ ሷศィ㸦No.007㸧෗┿㸲ࡣ࣡࢖ࣃ࣮௜ࡁࡢỈሷศィ࡛࠶ࡾࠊ㛗ᮇ࡟ࢃࡓࡿ࡜ィჾ࡟ࣇࢪࢶ࣎➼ࡢ㈅㢮ࡀ௜╔ࡋ ᐃࡀᅔ㞴࡟࡞ࡿࡓࡵ࡟࣡࢖ࣃ࣮ࢆ௜ࡅ࡚࠸ࡿሷศィ࡛࠶ࡿࠋᅗ 2 ࡟ほ ᆅⅬࢆ♧ࡍ㸦ᅗ 2▲༳㸧ほ ሙᡤ࡟ࡣ⃢➽ࡀ㏻ࡗ࡚࠸ࡿࡓࡵࡇࡢᆅⅬ࡛ࡢほࢆ⾜ࡗࡓࠋ෗┿ 5 ࡟ὶྥὶ㏿ィ࡜ሷศィࡢタ⨨≧ἣࢆ♧ࡍࠋィჾタ⨨ࡣほ ᆅⅬ࡟⯪࡛⾜ࡁ⯪ୖࡼࡾ࣮ࣟࣉ࡟ᅛᐃࡋࡓὶྥὶ㏿ィ࡜ሷศィࢆྲྀࡾ௜ࡅࡓ࣮ࣟࣉ࡟㕲ࣃ࢖ࣉࢆ⦡ࡾ௜
ࡅ࡚ᅛᐃࡋࡓ(෗┿ 5)ࠋ

129

 ᅗ㸰 †ཱྀ࡟࠾ࡅࡿほ ఩⨨(‫   )ڸ‬෗┿㸳 ィ ᶵჾࡢタ⨨ᅗ 3 ࡣ 11/7~12/10 ࡲ࡛ࡢほࢆ⾜ࡗࡓ㝿ࡢᶵჾࡢタ⨨఩⨨࡛࠶ࡿࠋほ 㛤ጞ᫬ࡢỈ῝ࡣ

1.8m ࡔࡗࡓࠋὶྥὶ㏿ィ㸦No.104㸧ࡣᗏ㠃࠿ࡽ 0.8mࠊỈሷศィ㸦No.1060㸪1061㸧ࡣࡑࢀࡒࢀᗏ㠃࠿ࡽ 1.2mࠊ1.5mࠊ
㸦No.336㸪337㸪007㸧ࡣ 0.3mࠊ0.6mࠊ0.9m ࡢ఩⨨࡟タ⨨ࡋࡓࠋᅗ㸱 ሷศỈ ィ࠾ࡼࡧὶྥὶ㏿ィࡢタ⨨఩⨨

3. 㐳ୖሷỈࡢሷศ㖄┤ศᕸࡢ᳨ウ †ཱྀࡼࡾ  ੊ୗὶ࡟࠶ࡿ㧗℩ᶫ࡟࠾ࡅࡿሷỈࡢΰྜᙧែࡣᙉΰྜࡀከࡃሷศࡢ㖄┤ศᕸࡣ↓ど࡛ࡁࡿ࡜ࡋࡓㄪᰝ◊✲ࡀከ࠸ࠋࡋ࠿ࡋࠊ†ཱྀࡲ࡛㐍ࡴሷỈࡣ㖄┤ศᕸࡀ኱ࡁࡃ࡞ࡾࠊሷศࡢศᩓࡣ↓ど࡛ࡁ࡞࠸ࠋ ᖺᗘ࡟ほศᕸࡼࡾᚓࡽࢀࡿ㐍ධሷỈሢࡢ㖄┤ศᕸࢆ᳨ウࡋ࡚ࡳࡿࠋࡋࡓሷศ130 †ཱྀ࡟࠾ࡅࡿὶ㏿ࡣྂᮧ࣭బࠎᮌ࣭ຌย㸦㸧࡟ࡼࡿἙཱྀỈ఩࡜†Ỉ఩࡟ࡼࡾḟᘧࡢࡼ࠺࡟୚࠼ࡽࢀࡿࠋ
V㸻0.122ටʹ㹥Ǽ㹸 Ǽ㹸㸼0 㸦㡰ὶ㸧                 㸦1㸧V㸻0.22ටʹ㹥㹺Ǽ㹸㹺 Ǽ㹸㸺0 㸦㏫ὶ㸧                 㸦2㸧ࡇࡇ࡟ࠊǼ㹸=㹘΁-㹘΂        㹘΁㸸ᑠᕝཎ†ࡢỈ఩  㹘΂㸸㧗℩ᕝἙཱྀࡢỈ఩ᘧ㸦 ࠾ࡼࡧ㸦㸰㸧࡟࠾࠸࡚ࠊ㡰ὶࡣ†࠿ࡽᾏ࡬ྥ࠿࠺ὶࢀࠊ㏫ὶࡣᾏ࠿ࡽ†࡟ྥ࠿࠺ὶࢀࢆព࿡ࡋ࡚࠸ࡿࠋᘧ  ࠾ࡼࡧ㸦㸰㸧࡟ࡼࡾ୚࠼ࡽࢀࡿ  ᖺ ᭶ࡢὶ㏿ࡣᅗ㸲࡟♧ࡍࡼ࠺࡟࡞ࡿࠋ
0.4
0.3
0.20.10-0.1-0.2-0.3
-0.4
-0.5

㹫/㹱㡰ὶ

68

1012

14

16

18

202224dayᅗ㸲 ᑠᕝཎ††ཱྀ࡟࠾ࡅࡿ㡰ὶ࡜㏫ὶ㸦2016 ᖺ 10 ᭶㸧ᅗ㸲࡟♧ࡍࡼ࠺࡟㏫ὶࡣ࡯ࡰ㐃᪥⏕ࡌ࡚࠸ࡿࠋࡋ࠿ࡋࠊ†ཱྀ࡟฿㐩ࡍࡿሷỈࡣ㝈ࡽࢀ࡚࠾ࡾ㏫ὶࡢ⥅⥆᫬㛫ࡀ㛗ࡃࠊ኱ࡁ࡞㏿ᗘ࡟㐩ࡍࡿ࡜ࡁࡔࡅ࡛࠶ࡾࠊ᭶  ᪥࠿ࡽ  ᪥࡟࠿ࡅ࡚ሷỈࡀ†ཱྀ࡟฿㐩ࡍࡿࠋᅗ㸳࡟ୗᒙࡢሷศண ࢆ♧ࡋࡓࠋࡇࡇ࡟ࠊሷศࡢண ࡣ 6DVDNL7DQDNDDQG8PHGD  ࡀ௨ୗࡢࡼ࠺࡟♧ࡋࡓ⌮ㄽ࡟ࡼࡾィ⟬ࡋ࡚࠸ࡿࠋࡍ࡞ࢃࡕࠊ㏫ὶ᫬࡟ࡣ㖄┤᪉ྥ࡟ศ๭ࡋࡓྛᒙࡢሷศ⃰ᗘ c ࡣỈᗏ࠿ࡽỈ㠃ࡲ࡛ࡢ඲Ỉᒙࢆ㹬ศ๭ࡋࡓ᫬ࡢ㹩␒┠ࡢỈᒙෆ࡟࠾࠸࡚ḟᘧ(3)࡛
୚࠼ࡽࢀࡿࠋ

ck

C max k  C min k {1  exp(D 1k [ k )}  C min kck

C min k at[k0                (㸱)                          (4)131[katfck

C max k[kE1 k ³ u k dt / l o  E 2 k x k / l o  l o1 k / l o                         (5)                㸦6㸧ᘧ㸦6㸧࡟࠾࠸࡚ࠊt, ࠾ࡼࡧ x ࡣ᫬㛫ࠊ࠾ࡼࡧὶ㊰࡟ἢ࠺㝣࠿ࡽᾏ࡬ྥ࠿ࡗ࡚ྲྀࡽࢀࡓᗙᶆࠊ
u k ࡣὶ㏿,㹪0 ࡣሙࡢ௦⾲ⓗ࡞㛗ࡉ࡛࠶ࡾࠊࡇࡇ࡛ࡣ㹪0㸻㸱㸴㸮㸮㹫࡜ࡋ࡚࠾ࡾࠊș㸯 ࠾ࡼࡧș㸰ࡣ௵ពࡢᐃᩘ࡛࠶ࡾࠊ㏫ὶ᫬࡟ș㸯㸻㸯ࠊș㸰㸻㸱ࠊ㡰ὶ᫬࡟ș㸯㸻㸯ࠊș㸰㸻̿㸱ࠊ
Lo1 ࡣ㏫ὶ㛤ጞ᫬ࡢሷỈࣇࣟࣥࢺࡢ఩⨨࡟┦ᙜࡍࡿ㊥㞳࡛࠶ࡿࠋ㡰ὶ᫬࡟ࡣሷศ⃰ᗘࡣḟᘧ(5)࡟ࡼࡾ୚࠼ࡽࢀࡿࠋ

ck

C pk  C min k exp{D 2 k ([ k  [ ok )}  C min kckCpkck

C min kat a [ k[ oktas [ k(7)[k t 0(8)f(9)ࡇࡇ࡟ࠊ᫬㛫㹲ࡣ㡰ὶ㛤ጞ᫬࡟㸮࡜࡞ࡿࠋࡲࡓࠊᘧ(7)࡟࠾࠸࡚ࠊ㹁㹮㹩ࡣ㡰ὶ㛤ጞ᫬ࡢሷศሷศ⃰ᗘ㸦㹎㹑㹓㸧⃰ᗘ࡛࠶ࡿࠋᘧ㸦3㸧࠾ࡼࡧ㸦7㸧ࡼࡾࠊ㏫ὶ࠾ࡼࡧ㡰ὶ᫬ࡢሷศࡀィ⟬ࡉࢀࡿࠋ

30
ほ20

ᆅ

ィ⟬್

ୗᒙ(†ᗏ࠿ࡽ16㹡㹫)

10
0
6

8

10

12

14

16

18

20

22

24day
ᅗ㸳 ᑠᕝཎ†ཱྀ࡟࠾ࡅࡿ 2016 ᖺ 10 ᭶ࡢሷỈ㐳ୖࡇࡇ࡟ࠊሷศࡢィ⟬ࡣḟࡢቃ⏺᮲௳ࢆ⏝࠸࡚࠸ࡿࠋ
Ș΂=3.2ࠊȘ΃=1.5ࠊε΁΂=-1200ࠊε΁΃=0ࠊCm=33.5ࠊC΂=1.3     (10)

ྂᮧ࣭బࠎᮌ࣭ຌย࡟ࡼࡿ࡜ୖᒙ ᗏ㠃࠿ࡽ  ੉ࡢ㧗ࡉ ࡢ⌮ㄽᐃᩘࡣ௨ୗࡢࡼ࠺࡟࡞ࡿࠋ
Ș΂=2.7ࠊȘ΃=1.0ࠊε΁΂=-1300ࠊε΁΃=0ࠊCm=33.5ࠊC΂=1.3     (11)ᅗ㸴ࡣᘧ  ࠾ࡼࡧ  ࡟ࡼࡾ୚࠼ࡽࢀࡿ  ᖺ  ᭶ࡢ†ཱྀ࡟࠾ࡅࡿ㐍ධሷỈࡢሷศศᕸࢆ♧ࡋ࡚࠾ࡾࠊୗᒙ࡜ୖᒙࡢ  ᒙࡼࡾሷศศᕸࢆண ࡋࡓ⤖ᯝࢆ♧ࡋ࡚࠸ࡿࡀ㖄┤ศᕸࡣࡉࡽ࡟ኚ໬ࡋࡓ᪉ࡀ⮬↛࡟ぢ࠼ࡿࠋࡑࡇ࡛ࠊ ᒙࡢሷศண ⤖ᯝࡼࡾ㖄┤ศᕸࢆண ࡋࡓࡢࡀᅗ㸵࡛࠶ࡿࠋᅗ㸵ࡼࡾࠊሷศࡢ㖄┤ኚ132໬ࡣ  ᒙࡢሙྜࡣࡼࡾ⮬↛࡟ぢ࠼ࡿࠋࡍ࡞ࢃࡕࠊࡇࡇ࡟ධࡿሷỈࡢ㖄┤ศᕸࡣ↓ど࡛ࡁ࡞࠸ࡇ࡜ࢆ♧ࡋ࡚࠸ࡿࠋᅗ㸴 †ཱྀ࡟㐍ධࡍࡿሷỈࡢሷศ㖄┤ศᕸ㸦2016 ᖺ 10 ᭶㸧㸦2 ᒙࡢሙྜ㸧ᅗ㸵 †ཱྀ࡟㐍ධࡍࡿሷỈࡢሷศ㖄┤ศᕸ㸦2016 ᖺ 10 ᭶㸧㸦4 ᒙࡢሙྜ㸧㸲㸬⤖ࡧ †ཱྀ࡟㐍ධࡍࡿሷỈࡢሷศ㖄┤ศᕸࡣ↓ど࡛ࡁ࡞࠸ࡇ࡜ࢆ᫂ࡽ࠿࡟ࡋࡓࠋཧ⪃ᩥ⊩(㸯) ྂᮧ᭸ஓ࣭బࠎᮌᖿኵ࣭ຌย ᬛ㸸ᑠᕝཎ†ỶỈ⎔ቃㄪᰝࠊᮾ໭ᆅᇦ⅏ᐖ⛉Ꮫ◊✲ࠊ➨ 53 ᕳࠊ
pp.77-82,2017.03.
(㸰)

Mikio Sasaki, Tanaka H. and Umeda M. “Characteristics of Salt Water Movement in Iwaki

River Estuary, Japan ” Journal of Earth Science and Engineering, Vol. 7, No.1, pp10-19,2017.