Geography – Continuous Ria coastlines from Omoe, the easternmost point of Honshu, to Kinkasan –

From around Miyako in Iwate Prefecture to the Oshika Peninsula in Miyagi Prefecture, the Ria coastline alternates between inlets and peninsulas. Both to the northern and southern areas, the coastline uplifted, and subsequent erosion by rivers formed the terrain. However, in the southern regions, the sea level rose faster than the rate of uplift, resulting in a complex and intricate coastline. Additionally, the Omoe Peninsula is the easternmost peninsula of Honshu and the largest peninsula in Sanriku.

The strata of the southern Kitakami Belt, south of Mt. Hayachine and inland of Miyako, are some of the oldest in Japan. This area showcases a continuous sequence of strata from the Silurian period (approximately 440 million years ago)—fossils from this period were first discovered in Japan—to the Triassic period (approximately 250 million years ago). Notably, the oldest ichthyosaur fossils were found in the Triassic strata of Kesennuma, providing valuable insights into the recovery process of life after mass extinctions.

These strata contain abundant mineral resources such as gold and magnetite, serving as the source of wealth for the Gold Culture of Hiraizumi and the modern steelmaking history of Kamaishi, both of which are UNESCO World Heritage sites. Even today, limestone, the raw material for cement, which is a major industry in Ofunato, is mined in this area.

Preserving the Traces of Numerous Tsunamis for Future Generations

The Sanriku region is known as a frequent tsunami-stricken area. The complex terrain of the Ria coastline amplifies the damage caused by tsunamis. V-shaped inlets narrow and become shallower as they approach the land, causing the energy of tsunamis to increase and heighten as they move toward land. In some areas, the tsunami height reached up to 30 meters during the Meiji Sanriku Tsunami. Due to the steep slopes, settlements have historically formed in flat coastal areas, with mountains looming immediately behind. Though each region in Sanriku works to pass down the experience and lessons of tsunamis, this area, in particular, has many monuments left behind to convey the importance of evacuation to future generations.

Vegetation – The northern limit of evergreen broadleaf trees: camellias, yuzu, Japanese blue oak, and more –

The vicinity of Miyako marks the northern limit of evergreen broadleaf trees along the Pacific coast. Species such as camellias, Japanese blue oaks, Japanese snowbells, and Japanese holly, with glossy leaves that do not shed, are not found farther north. Additionally, the northern limit of the fir tree forest, a coniferous tree, is said to be within the precincts of Kuromori Shrine in Miyako. The islands Funakoshi Oshima (Yamada Town), known as Oshima of Japanese blue oak, and Sanganjima (Kamaishi) are home to groves of Japanese blue oak trees because of the warmer climate the Kuroshio Current causes.

With a warmer climate and less influence of yamase (cold northeast winds), the Kesen District (Ofunato, Rikuzentakata) has a custom of planting evergreen trees like camellias, tea, and yuzu in people’s gardens to use communally. Some are actively cultivated as specialty products.

The mudflats at the back of Miyako Bay, located at the mouth of the Tsugaruishi River, are the largest tidal flats in Iwate Prefecture, where clam fishing is also conducted; sea milkwort, a plant that grows in brackish marshes, can be found along the muddy shores.

At Todogasaki, the easternmost point of Honshu, seaside plants such as beach daisies, Ezo hawkweeds, and beach evening primroses inhabit the coastal cliffs. Natural forests of Japanese cedars can also be observed. The Funakoshi Peninsula, where one can climb Mt. Karogatake, a popular mountain with a 514-meter summit, boasts natural beech forests on its eastern side, making it one of the few areas along the Pacific coast where beech trees grow.

In the Machikata area at Otsuchi’s town center, water springs up everywhere. Before the Great East Japan Earthquake, there were around 90 naturally occurring springs and wells, which were used for domestic water. Many of them were buried due to reconstruction efforts, but on the south side of the Sanriku Railway, a biotope utilizing spring water was developed. The Itoyo, a freshwater fish, inhabits the Gensui River in the town and is designated as a natural monument of the town.

Nehama Beach, facing Otsuchi Bay, is a beach with white sand and green pine trees. While the tsunami washed away much of the sandy beach at the mouth of the Unosumai River, restoration efforts have revived the sandy beach. The pine forest on the beach, which withstood the tsunami damage, was planted as a seawall forest in response to the lessons learned from past tsunamis. Around the sandy beach and pine forest, residents have planted seaside plants such as Japanese beach silvertop, false bindweed, and beach pea bloom.

Farther south from Otsuchi Bay, several long and narrow peninsulas jut out, with settlements around each inlet. In the Koshikira area of Sanriku Town, Ofunato, a giant poplar tree known as “Indomitable Poplar,” stands, having endured the tsunami. Nearby is the Sanriku Daio Sugi (Sanriku King Cedar), said to be 7,000 years old.

At Goishi Coast, while walking through pine forests, one can enjoy various landscapes created by rocks, waves, and the passage of time, such as the Anatoshi-iso through-hole and Kaminari-iwa thunder rock. From the observation deck, you can also see Ayasato Cape on the opposite shore.

The Ono Coast (Rikuzentakata), facing Ono Bay, has been the focus of conservation efforts for coastal plants by local elementary school students since the earthquake and tsunami. In early summer, false bindweed and Japanese beach silvertop bloom across the area. The Takata Matsubara Beach finally reopened for swimming in 2021, marking the first time since the tsunami. Local groups and the prefecture planted 40,000 pine trees between the seawall and the sandy beach.

The closure of part of Hirota Bay formed the lagoon Furukawa Numa at the mouth of the Kesen River as it reaches the bay. During past tsunamis, it often merged with the sea. Plants that inhabit brackish environments where freshwater and seawater mix can be found here. This area serves as a wintering ground for swans and pintails.

At the Oya Coast, after the disaster, there was a plan to build a seawall that would bury the entire sandy beach. However, discussions with local residents and persistent negotiation allowed the seawall to be set back to preserve the sandy beach. The community achieved town building that improved the safety by elevating roads and other measures.

Towns – Port Town –

*Miyako, Kamaishi, and Kesennuma have transformed from fishing villages to port towns

The Sanriku coastline, with its deep waters compared to the cliffs on the northern side and the plains on the southern side, is well-suited for harbors, as it is less affected by winds and waves due to being sheltered by north and south capes. Moreover, it is a fertile fishing ground where fish gather due to abundant plankton, and people have lived off the bounty of the sea since the Jomon period.

Representative port towns along the Sanriku coast include Miyako, Kamaishi, and Kesennuma, which evolved from fishing villages into vital hubs for logistics since the early modern period. Under the geographical constraints of the Rias coastline, where flatlands are scarce, deep harbors were constructed by land reclamation beginning in the Edo period.

Miyako Port was designated as the domain port of the Nambu Domain by the feudal lord Nambu Toshinao in the wake of the Keicho Great Tsunami (1611). It dispatched products, such as fermented fish fertilizer and salted salmon made from sardines, to Edo (Tokyo today), while importing agricultural products such as cotton and tea, as well as secondhand clothes and paper from Edo.

Kamaishi at the mouth of the Kasshi River was once a small fishing village known as Yanoura, but it developed into a major transit point for the Tokugawa shogunate’s maritime transport system, along with the establishment of the Eastern Route Shipping service connecting Edo and Matsumae (Hokkaido). The wealthy Sano family sent marine products to Edo and Choshi. The first Japanese-made nautical chart, the Map of Kamaishi Port in Rikuchu Province, was drawn in the early Meiji period, and since the Showa era, Kamaishi has been utilized as an industrial port with the entry and exit of foreign ships.

Kesennuma before the Edo period had a harbor that extended much further inland than it does now. Reclamation work from the early Edo period was said to be for the development of a harbor to take advantage of the terrain suitable for large sailing ships waiting for the northwest wind. Furthermore, around the same time, the pole-and-line tuna fishing method was introduced from Kishu (Wakayama Prefecture) to Karakuwa in the northern part of the city, leading to its development in the city as one of Japan’s leading fishing ports.