Photo/Illutration Imazu Todai shines green in February in Nishinomiya, Hyogo Prefecture as evening closes in. A floodgate is being built behind it. (Kazuhiko Matsunaga)

NISHINOMIYA, Hyogo Prefecture--Japan’s oldest surviving wooden lighthouse here is changing sentry duty for the first time in more than 200 years.

Imazu Todai will be relocated across a river as part of work to shore up Imazu Port just west of Osaka against the threat of tsunami.

Its original appearance dating from the Edo Period (1603-1867) will be kept intact, but the color of light will change from green to red in accordance with law.

The beacon was originally built in 1810 to navigate boats transporting famed sake from Nishinomiya and surrounding areas to Edo, present-day Tokyo.

“It is a symbolic structure handed down over generations,” said an official of Ozeki Corp., a sake brewery that owns the lighthouse. “Every effort will be made to preserve the facility to pass down the history of our sake-producing area.”

Imazu Todai during the Taisho Era (Provided by Ozeki Corp.)

Erected on a stone foundation, Imazu Todai stands 6.7 meters tall. The lantern stand has a copper roof and a body fashioned from Japanese cedar.

According to the Nishinomiya board of education and other sources, Chobei Osabe, the fifth-generation head of Ozeki’s founding family, constructed the beacon with his own funds to wish for the safety of “tarukaisen” sake-carrying boats.

Imazu Todai was recognized in 1968 as a privately run navigational beacon by the Japan Coast Guard.

The education board, which describes the facility as “Japan’s oldest wooden lighthouse in operation,” designated it as an important tangible cultural property in 1974. The lighthouse is being patrolled daily by personnel from Ozeki.

In olden days, the lantern was lit with oil and covered by oil-applied shoji paper to protect it against the elements. When the facility was electrified during the Taisho Era (1912-1926), the oiled shoji was removed, and only the lattice remains.

Imazu Todai, photographed in 1959 (Provided by Ozeki Corp.)

The Hyogo prefectural government started work to protect Imazu Port from tsunami in 2016.

A floodgate is being built at the mouth of Shinkawa River because a long-anticipated megaquake along the Nankai Trough in the Pacific could channel tsunami upstream and cause extensive damage.

Imazu Todai needs to be moved closer to the sea than the floodgate if it is to continue operations as an active beacon.

Ozeki, which wanted to maintain the symbol of the history of the sake-producing area, agreed with prefectural authorities last summer to relocate the lighthouse to the opposite side of the river 200 meters southwest of its current location.

The relocation work is expected to begin in March next year.

The stone base, roof and body will be transported separately and reassembled to reproduce the beacon’s original appearance and retain its value as a cultural property.

Imazu Todai, which stands on the right bank of Shinkawa River, emits green light. According to the Aids to Navigation Law, green warns ships entering a port of “land or obstacles lying on the left side.”

The color of light will change to red for dangers on the right after it is relocated to the left bank of the river.