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| Sanuki Plain | |
|---|---|
| Name | Sanuki Plain |
| Native name | 讃岐平野 |
| Country | Japan |
| Prefecture | Kagawa Prefecture |
| Region | Shikoku |
| Area km2 | 300 |
| Population | 500000 |
| Notable cities | Takamatsu, Marugame, Sakaide |
Sanuki Plain The Sanuki Plain is a lowland region on the northern shore of Shikoku in Kagawa Prefecture, Japan. The plain extends across the Seto Inland Sea coast between the Takamatsu Basin and the mouth of the Yoshino River system, forming a prominent agricultural and urbanized area that includes Takamatsu, Marugame, and Sakaide. Its landscape, transport links, and cultural sites connect to wider networks such as the Seto Inland Sea maritime routes, the Honshu–Shikoku Bridge Project, and historical routes like the Shikoku Pilgrimage.
The plain occupies the northern part of Kagawa Prefecture along the northern coastline of Shikoku, bounded by coastal waters of the Seto Inland Sea and the low hills that lead toward the Sanuki Mountains. Major urban centers include Takamatsu, Marugame, Sakaide, and Zentsūji. Hydrographic features draining the plain feed into the Seto Inland Sea and connect with waterways such as the Koto River and tributaries of the Yoshino River system; nearby islands like Naoshima and Teshima influence coastal ecology and transport. The plain's location places it within the Setonaikai National Park buffer region and adjacent to infrastructural nodes of the Honshu–Shikoku Bridge Project and the Great Seto Bridge complex.
The Sanuki Plain is a Quaternary depositional plain formed by fluvial and marine sedimentation associated with the Seto Inland Sea basin subsidence and uplift phases linked to the Philippine Sea Plate and the Eurasian Plate interaction. Sediments include alluvial deposits from rivers and marine terraces influenced by past sea-level fluctuations during the Holocene and late Pleistocene. Nearby tectonic structures include the forearc basins and the uplifted ridges feeding colluvial material from the Sanuki Mountains. Seismic activity related to the Seto Inland Sea region and historical earthquakes recorded in Tokugawa-era annals have influenced paleoshorelines and reclamation projects.
The plain experiences a humid subtropical climate influenced by the Seto Inland Sea microclimate, with relatively mild winters and hot, humid summers. Seasonal patterns are affected by the East Asian monsoon and by maritime moderation from the Kuroshio Current offshore. Precipitation peaks during the tsuyu rainy season and is also affected by typhoon tracks that pass through the Nansei Islands corridor. Climatic conditions support cereal cultivation common in the plain and shape flood risk management tied to rivers and coastal defenses.
Human settlement of the plain dates to prehistoric and historical periods linked to the Yayoi period wet-rice agriculture expansion and later to feudal centers during the Muromachi period and Edo period. Feudal domains such as the Takamatsu Domain established castle towns including Marugame Castle and Takamatsu Castle (Sanuki) as regional administrative centers. The plain's towns feature temples on the Shikoku Pilgrimage route, including Zentsū-ji, and cultural festivals connected to the Setouchi Triennale contemporary art movement on nearby islands like Naoshima. Modernization in the Meiji era brought links to national railways such as Shikoku Railway Company lines and port development tied to trade with Okayama and Osaka.
Agriculture dominates flatland use, historically centered on rice paddies and now diversified to include udon-related wheat cultivation, horticulture, and greenhouse operations supplying regional markets like Takamatsu Port. Industrial zones near Sakaide and Marugame host manufacturing connected to chemicals, shipbuilding linked to Seto Inland Sea shipyards, and logistics supporting the Honshu–Shikoku Bridge Project. Urban expansion around Takamatsu drives residential and commercial land conversion, while fisheries operate from ports serving the Seto Inland Sea and processing facilities tied to prefectural brands. Regional economic planning involves institutions such as the Kagawa Prefectural Government and collaborations with universities like Kagawa University.
The plain is a transport hub integrating road, rail, and sea links. Major arteries include the National Route 11 (Japan), the Seto-Chuo Expressway connection to Honshu via the Great Seto Bridge, and rail services by Shikoku Railway Company including the Yosan Line. Ports at Takamatsu Port and Sakaide Port provide ferry services to islands such as Naoshima and maritime freight corridors to Okayama Port. Regional airports like Takamatsu Airport support domestic air links, while infrastructure projects such as the Honshu–Shikoku Bridge Project and local coastal defenses address seismic and flooding risks.
Coastal wetlands, tidal flats, and reclaimed agricultural areas on the plain provide habitats for migratory birds associated with the East Asian–Australasian Flyway and marine species of the Seto Inland Sea. Conservation efforts involve protected areas and initiatives by organizations including Ministry of the Environment (Japan) programs and prefectural biodiversity plans to balance agriculture, urbanization, and habitat preservation. Environmental challenges include eutrophication in enclosed bays, invasive species documented in marine surveys, and pressures from reclamation and port expansion addressed through regional environmental impact assessments and community-led restoration projects.
Category:Plains of Japan Category:Geography of Kagawa Prefecture