View source for Classification of rivers in Japan

{{Short description|System used by the Japanese government to classify rivers}}
[[File:NiigataCityOpenData machinami004.jpg|thumb|Shinano River, the longest river in Japan, designated as Class A]]
Rivers in [[Japan]] are classified according to criteria set by the {{nihongo|River Act|河川法|Kasen Hō}}, which was introduced in 1967.<ref name=":0">{{cite web|title=River Administration in Japan|url=http://www.mlit.go.jp/river/basic_info/english/admin.html|publisher=Ministry of Land, Infrastructure, Transport and Tourism|accessdate=December 31, 2017}}</ref><ref name="river law text">{{cite web|title=河川法|trans-title=River Law|url=http://www.houko.com/00/01/S39/167.HTM|url-status=dead|publisher=[[Ministry of Land, Infrastructure, Transport and Tourism]]|language=Japanese|accessdate=July 6, 2016|archiveurl=https://web.archive.org/web/20160623014717/http://www.houko.com/00/01/S39/167.HTM|archivedate=June 23, 2016}}</ref> Rivers are classified by the [[Ministry of Land, Infrastructure, Transport and Tourism]] (MLIT). 

== River Act ==

=== Pre-1967 river administration ===
At the beginning of the [[Meiji era]], river construction mainly consisted of low water construction such as securing water for boat transportation and irrigation, but after the middle of the Meiji era, boat transportation declined with the spread of railways, and on the other hand, development of river coasts exacerbated damage from floods. As the number of floods increased, a shift was made to high water construction to prevent flooding by building [[Levee|levees]].<ref name=":2">{{Cite web |title=社会経済の変化を踏まえた今後の河川制度のあり方について |url=https://www.mlit.go.jp/river/shinngikai_blog/past_shinngikai/shinngikai/shingi/to9612-1.html |access-date=2024-03-05 |website=[[Ministry of Land, Infrastructure, Transport, and Tourism]]}}</ref>

The old system was enacted in 1891 following the proclamation of the [[Meiji Constitution]]. As Japan's first modern public property management system, a systematic legal system for river management was established. However, due to the background of its enactment, the old River Law had strong overtones of control by state power, and, reflecting the social situation at the time, placed more emphasis on flood control than water utilization.<ref name=":2" />

=== New River Act ===
Over the following 70 years, due to post-war social and economic development, the use of river water for [[Hydroelectricity|hydroelectric power generation]] and industrial water increased rapidly<ref name=":2" /> and because of inconsistencies that had arisen in the system implemented by the old River Act, the new River Act was enacted in 1962, with the following changes:

* All rivers and river systems are classified into four classes<ref name=":2" />
* Entities in charge of rivers are required to formulate a plan for integrated water management<ref name=":2" />
* Establishment of regulations related to water use<ref name=":2" />
* Establishment of regulations to prevent disasters caused by dams<ref name=":2" />

=== 1997 amendment ===
The River Act was amended in 1997, changing its text to have a greater emphasis on conservation of natural environments, and the consultation and participation of local residents in forming water management plans.<ref name=":3">{{Cite journal |last1=Sakamoto |first1=Takaaki |last2=Shinozaki |first2=Yui |last3=Sato |first3=Hirokazu |last4=Shirakawa |first4=Naoki |last5=Kayaba |first5=Yuichi |date=2018-06-13 |title=IMPACT ASSESSMENT OF THE 1997 REVISED RIVER LAW ON CITIZEN PARTICIPATION IN THE ENVIRONMENTAL POLICIES OF RIVERS |url=https://www.jstage.jst.go.jp/article/river/24/0/24_379/_pdf |journal=Advances in River Engineering |volume=24 |via=J-STAGE}}</ref>

=== Impact ===
The 1967 River Act simplified the management of waterways in Japan by merging previously separate systems into one unified water management system.<ref name=":2" /><ref name=":4">{{Cite news |date=2015-10-29 |title=川づくりの来し方・行く末 ─ 河川法制定120周年に寄せて |url=https://www.jstage.jst.go.jp/article/jwei/29/1/29_jwei290101/_pdf |access-date=2024-03-05 |work=Journal of Water and Environmental Issues}}</ref> Before this, the river management system in Japan was seen as heavy-handed and overly bureaucratic.<ref name=":4" /> Especially post-1997 amendment, there is now greater community involvement when formulating plans regarding rivers and water management.<ref name=":3" />

== Class A rivers ==
{{nihongo|'''Class A river system'''|一級水系|Ikkyū suikei}} is a designation applied to rivers systems deemed to be important to the economy of the nation as a whole, as well as those deemed important to the conservation of nature within Japan. There are currently 109 river systems with this designation.<ref name="number of rivers">{{cite web|title=河川法第四条第一項の水系を指定する政令|trans-title=River Law Clause 4 Paragraph 1: River System Designation Ordinance|url=http://law.e-gov.go.jp/htmldata/S40/S40SE043.html|url-status=dead|publisher=e-Gov.go.jp|language=Japanese|accessdate=July 6, 2016|archiveurl=https://web.archive.org/web/20160305112253/http://law.e-gov.go.jp/htmldata/S40/S40SE043.html|archivedate=March 5, 2016}}</ref><ref name=":1">{{Cite web |title=よくある質問とその回答 |url=https://www.mlit.go.jp/river/basic_info/iken/question/faq_index.html |access-date=2024-03-05 |website=[[Ministry of Land, Infrastructure, Transport, and Tourism]]}}</ref> If a river system is designated Class A, all the constituent rivers are also designated as such. Therefore, Class B rivers cannot coexist with Class A rivers in the same river system.<ref name=":1" /> This designation is also called First Class.

{{Nihongo|'''Class A river'''|一級河川|Ikkyū kasen}} is a designation which applies to important individual rivers. There are 13,994 rivers with this designation.<ref name=":1" />

Generally speaking, areas surrounding Class A rivers will suffer greater damage in the event of a flood.<ref name=":1" />

=== List of Class A river systems ===
The number of [[Dam|dams]] only includes existing and unestablished dams that meet the criteria ({{Convert|15|m|ft}} or more in bank height) of the River Law. The management entity is irrelevant. The number in parentheses is the number of dams on the main river, excluding [[Tributary|tributaries]]. The number of dams does not always exceed the number of [[Hydroelectricity|hydroelectric plants]] because plants with intake [[Weir|weirs]] less than {{Convert|15|m|ft}} high are not considered dams. The acronym ''BOD'' refers to [[biochemical oxygen demand]].

Note: Okinawa has no Class A rivers.

==== Hokkaidō Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Teshio River|Teshio]]
|天塩川
|256
|5,590
| rowspan="13" |[[Hokkaido|Hokkaidō]]
|94,000
|160
|134.52
|0.7
|14 (2)
|3
|-
![[Shokotsu River|Shokotsu]]
|渚滑川
|84
|1,240
|28,000
|25
|29.33
|1.0
|0
|2
|-
![[Yūbetsu River|Yūbetsu]]
|湧別川
|87
|1,480
|36,000
|17
|32.45
|1.7
|1 (0)
|3
|-
![[Tokoro River|Tokoro]]
|常呂川
|120
|1,930
|142,000
|57
|22.64
|2.6
|2 (1)
|0
|-
![[Abashiri River|Abashiri]]
|網走川
|115
|1,380
|94,000
|25
|14.02
|2.5
|1 (0)
|2
|-
![[Rumoi River|Rumoi]]
|留萌川
|44
|270
|28,000
|13
|11.84
|1.5
|3 (0)
|0
|-
![[Ishikari River|Ishikari]]
|石狩川
|268
|14,330
|2,500,000
|464
|133.18
|1.1
|83 (1)
|34
|-
![[Shiribetsu River|Shiribetsu]]
|尻別川
|126
|1,640
|38,000
|40
|68.41
|0.4
|3 (0)
|7
|-
![[Shiribeshi-Toshibetsu River|Shiribeshi-Toshibetsu]]
|後志利別川
|80
|720
|16,000
|29
|23.69
|0.5
|2 (1)
|8
|-
![[Mu River (Hokkaidō)|Mu]]
|鵡川
|135
|1,270
|13,000
|20
|38.54
|0.6
|2 (0)
|1
|-
![[Saru River|Saru]]
|沙流川
|104
|1,350
|13,000
|28
|48.24
|0.6
|4 (2)
|4
|-
![[Kushiro River|Kushiro]]
|釧路川
|154
|2,510
|177,000
|38
|26.32
|1.7
|0
|0
|-
![[Tokachi River|Tokachi]]
|十勝川
|156
|9,010
|340,000
|209
|85.36
|1.7
|14 (3)
|16
|}

==== Tōhoku Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Iwaki River|Iwaki]]
|岩木川
|102
|2,540
| rowspan="2" |[[Aomori Prefecture|Aomori]]
|482,400
|97
|76.07
|1.6
|21 (2)
|5
|-
![[Takase River (Aomori)|Takase]]
|高瀬川
|64
|867
|80,372
|23
|50.10
|0.9
|3 (1)
|0
|-
![[Mabechi River|Mabechi]]
|馬淵川
|142
|2,050
|[[Iwate Prefecture|Iwate]], Aomori
|188,000
|30
|47.62
|1.1
|6 (0)
|5
|-
![[Kitakami River|Kitakami]]
|北上川
|249
|10,150
|Iwate, [[Miyagi Prefecture|Miyagi]]
|1,389,000
|302
|318.42
|1.1
|53 (1)
|33
|-
![[Naruse River|Naruse]]
|鳴瀬川
|89
|1,130
| rowspan="2" |Miyagi
|190,000
|61
|26.49
|1.3
|13 (1)
|3
|-
![[Natori River|Natori]]
|名取川
|55
|939
|1,125,589
|30
|17.32
|1.1
|9 (0)
|7
|-
![[Abukuma River|Abukuma]]
|阿武隈川
|239
|5,400
|Miyagi, [[Fukushima Prefecture|Fukushima]]
|1,380,000
|197
|52.22
|1.9
|19 (2)
|25
|-
![[Yoneshiro River|Yoneshiro]]
|米代川
|136
|4,100
|[[Akita Prefecture|Akita]], Iwate
|280,000
|89
|100.91
|1.3
|21 (0)
|22
|-
![[Omono River|Omono]]
|雄物川
|133
|4,710
| rowspan="2" |Akita
|346,481
|168
|259.02
|1.4
|34 (0)
|17
|-
![[Koyoshi River|Koyoshi]]
|子吉川
|61
|1,190
|80,000
|44
|60.60
|1.1
|12 (1)
|7
|-
![[Mogami River|Mogami]]
|最上川
|229
|7,040
| rowspan="2" |[[Yamagata Prefecture|Yamagata]]
|999,300
|429
|369.26
|1.0
|41 (1)
|26
|-
![[Aka River|Aka]]
|赤川
|70
|857
|109,294
|44
|65.68
|1.0
|5 (1)
|10
|}

==== Kantō Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Kuji River|Kuji]]
|久慈川
|124
|1,490
|Fukushima, [[Ibaraki Prefecture|Ibaraki]]
|201,981
|53
|23.58
|0.8
|1 (0)
|7
|-
![[Naka River (Tochigi Ibaraki)|Naka]]
|那珂川
|150
|3,270
|[[Tochigi Prefecture|Tochigi]], Ibaraki
|912,217
|197
|74.43
|0.9
|22 (2)
|12
|-
![[Tone River|Tone]]
|利根川
|322
|16,840
|[[Gunma Prefecture|Gunma]], [[Nagano Prefecture|Nagano]], Tochigi, [[Saitama Prefecture|Saitama]],
[[Tokyo]], [[Chiba Prefecture|Chiba]], Ibaraki
|12,140,000
|819
|237.10
|2.5
|70 (4)
|98
|-
![[Arakawa River (Kantō)|Ara]]
|荒川
|173
|2,940
|Saitama, Tokyo
|9,300,000
|127
|27.77
|4.4
|13 (2)
|11
|-
![[Tama River|Tama]]
|多摩川
|138
|1,240
|[[Yamanashi Prefecture|Yamanashi]], Tokyo, [[Kanagawa Prefecture|Kanagawa]]
|4,250,000
|52
|40.28
|1.7
|2 (2)
|5
|-
![[Tsurumi River|Tsurumi]]
|鶴見川
|43
|235
|Tokyo, Kanagawa
|1,840,000
|11
|7.83
|8.0
|0
|0
|-
![[Sagami River|Sagami]]
|相模川
|113
|1,680
|Yamanashi, Kanagawa
|1,200,000
|104
|－
|2.0
|10 (3)
|20
|-
![[Fuji River|Fuji]]
|富士川
|128
|3,990
|Nagano, Yamanashi, [[Shizuoka Prefecture|Shizuoka]]
|1,600,000
|555
|58.91
|2.3
|19 (0)
|71
|}

==== Hokuriku Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Arakawa River (Uetsu)|Ara]]
|荒川
|73
|1,150
|[[Yamagata Prefecture|Yamagata]], [[Niigata Prefecture|Niigata]]
|40,000
|61
|115.00
|0.6
|5 (3)
|6
|-
![[Agano River|Agano]]
|阿賀野川
|210
|7,710
|Fukushima, Gunma, Niigata
|590,000
|243
|401.55
|0.6
|62 (8)
|60
|-
![[Shinano River|Shinano]]
|信濃川
|367
|11,900
|Nagano, Gunma, Niigata
|2,950,000
|880
|503.15
|1.0
|90 (1)
|122
|-
![[Seki River|Seki]]
|関川
|64
|1,140
| rowspan="2" |Nagano, Niigata
|210,000
|78
|50.32
|1.5
|5 (1)
|16
|-
![[Hime River|Hime]]
|姫川
|60
|722
|20,000
|47
|44.07
|0.5
|0
|19
|-
![[Kurobe River|Kurobe]]
|黒部川
|85
|682
| rowspan="2" |[[Toyama Prefecture|Toyama]]
|71,000
|25
|37.00
|0.8
|6 (5)
|18
|-
![[Jōganji River|Jōganji]]
|常願寺川
|56
|368
|30,000
|49
|16.23
|0.6
|8 (1)
|27
|-
![[Jinzū River|Jinzū]]
|神通川
|120
|2,720
| rowspan="2" |[[Gifu Prefecture|Gifu]], Toyama
|380,000
|105
|183.65
|1.4
|25 (7)
|60
|-
![[Shō River|Shō]]
|庄川
|115
|1,180
|28,032
|48
|47.72
|1.0
|18 (9)
|27
|-
![[Oyabe River|Oyabe]]
|小矢部川
|68
|667
|[[Ishikawa Prefecture|Ishikawa]], Toyama
|300,000
|64
|27.99
|1.5
|14 (2)
|5
|-
![[Tedori River|Tedori]]
|手取川
|72
|809
| rowspan="2" |Ishikawa
|40,000
|35
|77.21
|0.5
|7 (2)
|24
|-
![[Kakehashi River|Kakehashi]]
|梯川
|42
|271
|110,000
|13
|18.02
|1.0
|1 (1)
|0
|}

==== Chūbu Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Kano River|Kano]]
|狩野川
|46
|852
| rowspan="4" |Shizuoka
|640,000
|76
|21.40
|1.5
|0
|7
|-
![[Abe River|Abe]]
|安倍川
|51
|567
|170,000
|36
|41.44
|0.8
|0
|2
|-
![[Ōi River|Ōi]]
|大井川
|168
|1,280
|90,000
|39
|76.40
|0.5
|14 (7)
|15
|-
![[Kiku River|Kiku]]
|菊川
|28
|158
|70,000
|25
|2.21
|1.8
|2 (0)
|0
|-
![[Tenryū River|Tenryū]]
|天竜川
|213
|5,090
|Nagano, [[Aichi Prefecture|Aichi]], Shizuoka
|720,000
|332
|239.67
|0.5
|17 (5)
|51
|-
![[Toyo River|Toyo]]
|豊川
|77
|724
|Aichi
|210,000
|27
|28.23
|0.6
|9 (1)
|3
|-
![[Yahagi River|Yahagi]]
|矢作川 or 矢矧川
|118
|1,830
|Nagano, Gifu, Aichi
|690,000
|94
|43.99
|1.0
|25 (3)
|25
|-
![[Shōnai River|Shōnai]]
|庄内川
|96
|1,010
|Gifu, Aichi
|2,500,000
|76
|26.21
|4.7
|18 (0)
|2
|-
![[Kiso River|Kiso]]
|木曽川
|229
|9,100
|Nagano, Gifu, [[Shiga Prefecture|Shiga]], 
Aichi, [[Mie Prefecture|Mie]]
|1,700,000
|391
|291.05
|0.7
|64 (9)
|77
|-
![[Suzuka River|Suzuka]]
|鈴鹿川
|38
|323
| rowspan="4" |Mie
|110,000
|46
|11.23
|1.4
|0
|0
|-
![[Kumozu River|Kumozu]]
|雲出川
|55
|550
|90,000
|40
|14.36
|1.6
|6 (0)
|1
|-
![[Kushida River|Kushida]]
|櫛田川
|85
|461
|40,000
|68
|20.55
|0.7
|4 (0)
|5
|-
![[Miya River (Mie)|Miya]]
|宮川
|91
|920
|140,000
|55
|45.70
|0.5
|5 (2)
|6
|}

==== Kinki Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Kuzuryū River|Kuzuryū]]
|九頭竜川
|116
|2,930
|Gifu, [[Fukui Prefecture|Fukui]]
|666,225
|147
|108.26
|0.8
|20 (3)
|25
|-
![[Kita River|Kita]]
|北川
|30
|211
|[[Shiga Prefecture|Shiga]], Fukui
|21,389
|12
|11.68
|0.6
|1 (0)
|1
|-
![[Yura River (Japan)|Yura]]
|由良川
|146
|1,880
|[[Hyōgo Prefecture|Hyōgo]], [[Kyoto Prefecture|Kyōto]]
|300,000
|138
|52.09
|0.8
|22 (3)
|6
|-
![[Yodo River|Yodo]]
|淀川
|75
|8,240
|Shiga, Kyōto, [[Osaka Prefecture|Ōsaka]],
Mie, [[Nara Prefecture|Nara]], Hyōgo
|11,650,000
|965
|267.51
|1.9
|66 (1)
|34
|-
![[Yamato River|Yamato]]
|大和川
|68
|1,070
|Nara, Ōsaka
|2,150,000
|178
|23.94
|3.3
|11 (1)
|0
|-
![[Maruyama River|Maruyama]]
|円山川
|68
|1,300
| rowspan="3" |Hyōgo
|150,557
|97
|37.40
|0.9
|7 (0)
|5
|-
![[Kako River (Japan)|Kako]]
|加古川
|96
|1,730
|640,000
|130
|45.89
|2.6
|19 (0)
|0
|-
![[Ibo River|Ibo]]
|揖保川
|70
|810
|200,000
|47
|29.04
|0.8
|4 (0)
|6
|-
![[Kinokawa River|Kino]]
|紀の川
|136
|1,750
|Nara, [[Wakayama Prefecture|Wakayama]]
|689,000
|181
|58.77
|2.1
|9 (2)
|6
|-
![[Kumano River|Kumano]]
|熊野川
|183
|2,360
|Nara, Mie, Wakayama
|84,000
|103
|163.54
|1.3
|11 (5)
|30
|}

==== Chūgoku Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Sendai River|Sendai]]
|千代川
|52
|1,190
| rowspan="3" |[[Tottori Prefecture|Tottori]]
|200,000
|87
|61.68
|0.8
|6 (0)
|17
|-
![[Tenjin River|Tenjin]]
|天神川
|32
|490
|65,500
|32
|24.03
|1.2
|8 (0)
|8
|-
![[Hino River|Hino]]
|日野川
|77
|870
|60,800
|56
|33.55
|1.1
|12 (0)
|14
|-
![[Hii River|Hii]]
|斐伊川
|153
|2,070
|[[Shimane Prefecture|Shimane]], Tottori
|435,000
|227
|40.26
|1.4
|24 (2)
|13
|-
![[Gōnokawa River|Gōno]]
|江の川
|194
|3,900
|[[Hiroshima Prefecture|Hiroshima]], Shimane
|202,000
|293
|75.17
|0.8
|20 (2)
|24
|-
![[Takatsu River|Takatsu]]
|高津川
|81
|1,090
|Shimane
|38,600
|92
|51.88
|0.7
|4 (0)
|5
|-
![[Yoshii River|Yoshii]]
|吉井川
|133
|2,110
| rowspan="2" |[[Okayama Prefecture|Okayama]]
|294,000
|215
|61.16
|2.0
|30 (1)
|18
|-
![[Asahi River|Asahi]]
|旭川
|142
|1,810
|335,000
|147
|57.01
|1.8
|25 (3)
|9
|-
![[Takahashi River|Takahashi]]
|高梁川
|111
|2,670
| rowspan="2" |Okayama, Hiroshima
|273,000
|121
|61.81
|2.5
|29 (1)
|19
|-
![[Ashida River|Ashida]]
|芦田川
|86
|860
|269,000
|82
|12.73
|4.0
|18 (2)
|3
|-
![[Ōta River|Ōta]]
|太田川
|103
|1,710
|Hiroshima
|980,000
|73
|78.81
|0.9
|11 (2)
|24
|-
![[Oze River|Oze]]
|小瀬川
|59
|340
|Hiroshima, [[Yamaguchi Prefecture|Yamaguchi]]
|26,500
|23
|12.05
|2.6
|4 (2)
|6
|-
![[Saba River (Japan)|Saba]]
|佐波川
|56
|460
|Yamaguchi
|31,100
|32
|18.69
|0.7
|4 (1)
|1
|}

==== Shikoku Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Yoshino River|Yoshino]]
|吉野川
|194
|3,750
|[[Kōchi Prefecture|Kōchi]], [[Ehime Prefecture|Ehime]], [[Tokushima Prefecture|Tokushima]], [[Kagawa Prefecture|Kagawa]]
|641,000
|356
|107.67
|0.8
|23 (4)
|32
|-
![[Naka River (Tokushima)|Naka]]
|那賀川
|125
|874
|Tokushima
|59,000
|75
|62.88
|0.7
|4 (3)
|5
|-
![[Doki River|Doki]]
|土器川
|33
|140
|Kagawa
|35,000
|11
|1.83
|3.9
|2 (0)
|0
|-
![[Shigenobu River|Shigenobu]]
|重信川
|36
|445
| rowspan="2" |Ehime
|233,000
|75
|2.24
|5.0
|8 (0)
|1
|-
![[Hiji River|Hiji]]
|肱川
|103
|1,210
|112,000
|475
|37.61
|1.0
|8 (2)
|4
|-
![[Monobe River|Monobe]]
|物部川
|71
|508
|Kōchi
|40,000
|35
|30.78
|0.7
|4 (3)
|6
|-
![[Niyodo River|Niyodo]]
|仁淀川
|124
|1,560
| rowspan="2" |Ehime, Kōchi
|105,000
|166
|100.07
|0.7
|5 (3)
|18
|-
![[Shimanto River|Shimanto]]
|四万十川
|196
|2,270
|100,000
|319
|121.02
|0.6
|5 (0)
|6
|}

==== Kyūshū Development Bureau ====
{| class="wikitable"
!Name
!Japanese
!Main stream length (km)
!Basin area (km<sup>2</sup>)
!Basin management
!Basin area population
!Tributaries
!Average annual flow rate (m<sup>3</sup>/s)
!BOD (ppm)
!Dams
!Hydroelectric plants
|-
![[Onga River|Onga]]
|遠賀川
|61
|1,026
|Fukuoka
|666,406
|74
|31.47
|2.6
|23 (0)
|1
|-
![[Yamakuni River|Yamakuni]]
|山国川
|56
|540
|[[Ōita Prefecture|Ōita]], Fukuoka
|36,801
|39
|20.81
|0.9
|1 (0)
|1
|-
![[Chikugo River|Chikugo]]
|筑後川
|143
|2,863
|[[Kumamoto Prefecture|Kumamoto]], Ōita, Fukuoka, [[Saga Prefecture|Saga]]
|1,090,777
|235
|95.09
|1.6
|29 (2)
|22
|-
![[Yabe River|Yabe]]
|矢部川
|61
|647
|[[Fukuoka Prefecture|Fukuoka]]
|182,889
|23
|21.54
|1.1
|17 (2)
|4
|-
![[Matsuura River]]
|松浦川
|47
|446
|Fukuoka, Saga
|97,818
|80
|12.46
|2.4
|22 (0)
|3
|-
![[Rokkaku River|Rokkaku]]
|六角川
|47
|341
| rowspan="2" |Saga
|122,827
|79
|4.36
|2.1
|9 (1)
|0
|-
![[Kase River|Kase]]
|嘉瀬川
|57
|368
|133,412
|51
|14.10
|1.0
|3 (2)
|8
|-
![[Honmyō River|Honmyō]]
|本明川
|21
|87
|[[Nagasaki Prefecture|Nagasaki]]
|54,583
|18
|2.11
|1.8
|2 (1)
|0
|-
![[Kikuchi River|Kikuchi]]
|菊池川
|71
|996
| rowspan="4" |Kumamoto
|208,694
|68
|39.56
|1.1
|1 (0)
|4
|-
![[Shirakawa River (Kumamoto)|Shira]]
|白川
|74
|480
|131,375
|16
|25.39
|2.5
|3 (1)
|4
|-
![[Midori River|Midori]]
|緑川
|76
|1,100
|517,189
|59
|36.17
|2.4
|4 (2)
|11
|-
![[Kuma River (Japan)|Kuma]]
|球磨川
|115
|1,880
|137,375
|82
|119.92
|1.4
|11 (4)
|20
|-
![[Ōita River|Ōita]]
|大分川
|55
|650
| Ōita
|252,808
|48
|22.33
|1.4
|7 (1)
|14
|-
![[Ōno River|Ōno]]
|大野川
|107
|1,465
| rowspan="2" |Kumamoto, [[Miyazaki Prefecture|Miyazaki]], Ōita
|206,818
|138
|61.36
|0.6
|14 (0)
|10
|-
![[Banjō River|Banjō]]
|番匠川
|38
|464
|56,527
|52
|12.17
|1.1
|5 (0)
|0
|-
![[Gokase River|Gokase]]
|五ヶ瀬川
|106
|1,820
|Miyazaki
|127,638
|102
|60.94
|1.1
|8 (2)
|22
|-
![[Omaru River (Miyazaki)|Omaru]]
|小丸川
|75
|474
|Miyazaki
|32,616
|16
|32.76
|0.5
|8 (4)
|5
|-
![[Ōyodo River|Ōyodo]]
|大淀川
|107
|2,230
|[[Kagoshima Prefecture|Kagoshima]], Miyazaki
|601,321
|134
|107.61
|1.3
|16 (2)
|12
|-
![[Sendai River (Kumamoto)|Sendai]]
|川内川
|137
|1,600
|Kumamoto, Miyazaki, Kagoshima
|195,944
|129
|91.09
|0.7
|4 (3)
|5
|-
![[Kimotsuki River|Kimotsuki]]
|肝属川
|34
|485
|Kagoshima
|115,578
|36
|31.69
|4.5
|2 (0)
|3
|}

==Class B rivers==
[[File:NanakitaGawa2005-5.jpg|thumb|The Nanakita River, a Class B river in Miyagi Prefecture]]
Smaller or less important rivers are designated as {{Nihongo|'''Class B river systems'''|二級水系|Nikyū Suikei}}. They are nominated and managed by the local governments at the [[Prefectures of Japan|prefecture level]], but reported to and concurred with by the central government.<ref name=":0" /> There are 7,090 rivers with this designation.<ref name=":1" /> Because all of their river systems are designated Class A, there are no Class B rivers in Saitama and Shiga prefectures.<ref name=":1" />

This designation is also called Second Class.

== ''Mutatis mutandis'' rivers ==
14,314 rivers in Japan are designated as {{Nihongo|[[mutatis mutandis]] rivers|準用河川|Junyō kasen}}, meaning that they are not assigned Class A or B designation, and are under the control of the mayor of the encompassing [[Cities of Japan|municipality]].<ref name=":5">{{Cite web |title=小田原市 {{!}} 1級河川、2級河川、準用河川、普通河川とは何ですか。 |url=https://www.city.odawara.kanagawa.jp/faq/p05927.html |access-date=2024-03-05 |website=小田原市 |language=ja}}</ref> An example of this is the Kuno River, managed by the mayor of [[Odawara]].<ref name=":5" />

== Ordinary rivers ==
Rivers that are not designated Class A, Class B, or ''mutatis mutandis'', are called {{Nihongo|ordinary rivers|普通河川|Futsū kasen}}, and the 1967 River Act does not apply to them.<ref name=":5" /> These do not include public sewers or agricultural canals.<ref>{{Cite web |title=普通河川とは？｜株式Rise |url=https://www.rise-jms.jp/media/kensetsu_yougo/a867 |access-date=2024-03-05 |website=株式会社Rise |language=ja}}</ref> Management of these rivers is carried out by the local municipality.<ref>{{Cite web |title=普通河川 |url=https://www.thr.mlit.go.jp/yamagata/river/enc/words/06ha/ha-006.html |access-date=2024-03-05 |website=www.thr.mlit.go.jp}}</ref>

== See also ==

* [[List of rivers of Japan]]
* {{section link|Natural disasters in Japan|Floods}}

==References==
{{reflist}}

{{Rivers of Japan}}

[[Category:Environmental law in Japan]]
[[Category:Rivers of Japan|/]]