Compare the terrain of dug-in ports in aerial photographs

Published: August 11, 2026 / About 17 min read

Fill in the sea, or dig into the land

The ways of building a new port fall broadly into two. One is reclamation, which carries earth and sand to the sea side to push the land out; the other is digging in, which digs down into land on the inner side of the coast to create a water surface. Reclamation is chosen, in many cases, where a shallow sea continues far offshore and there is no spare flat land to use behind it. Digging in is the opposite, and it works on coasts where shallow sandy beaches and sand dunes extend for a long way and land of limited use spreads behind them. Being able to send the dug earth and sand straight to the grading of the adjoining land was also an advantage of this method.

The choice of digging into the land to create a water surface takes shape in the aerial photographs. If you step through the eras in order, the shores of reclamation grow straight out toward the sea, while the water surfaces of digging in cut into the inner side of the land. Just by switching eras at the same position in the same frame, you can tell apart the difference in the direction in which the outlines extend.

Ports built by digging in share one more way of appearing. Almost nothing like a port appears in the photograph from the oldest era. In a port that uses an inlet or a river mouth, the water surface is there before ships come alongside. In a port made by digging into the land, the water surface itself appears later. A surface occupied by fields, wild land, or a band of sand is replaced in the next era by dark-colored water. This gap is the clue when you trace dug-in ports.

Kashima, where fields on sand dunes became a shipping channel

For the industrial area placed on the dune land along the Kashima-nada Sea, four eras are available: 1961-69, 1974-78, 1979-83, and 1984-86. You can follow in stages how the surface that was sandy fields came to be filled with facilities and piles of raw materials.

The oldest photograph is black and white. The sea is only the area from the upper right along the right edge, and white streaks of waves line up diagonally. The water's edge forms a line tilted from north-northeast to south-southwest, and inside it a bright band of sand extends widely. Not a single structure for bringing ships alongside, neither a breakwater nor a quay, appears. If you turn your eyes to the land, the frame is filled with fields to the corners. Toward the interior there is a grid of large single lots, and toward the sea there are long, narrow strips not facing the same way, with dark masses of woods and small clusters of houses between them.

If you switch to 1974-78, a dark navy channel thrusts diagonally from northeast to southwest into the right side, which was sea. Both banks are fixed with straight seawalls, and at the far end there is a square cut enclosed by white seawalls. The straight lines of the edges show that the water did not come in from outside but was led through the land side. On the surface where there had been fields, tall tower-like structures and chimneys gather, and at the lower right several dozen white round tanks are grouped. The grid of the fields does not remain.

In 1979-83 the facilities in the center increase in density and extent, and on the east side a dark surface opens where many long bands line up. By 1984-86 the colors of those bands can be seen split in two, black and reddish-brown. In the photograph as of 2026, gray-purple to black yards and rows of rust-red roofs spread out, and a large ship with a red hull lies alongside a quay. The lot at the upper right, where only the layout of roads had been put in in 1984-86, has changed into the green of lawns and trees and tanks.

Tomakomai, dug inland from the southern end of a wild plain

A corner of a sandy beach facing the Pacific Ocean cuts squarely toward the interior. This is the West Port of Tomakomai, which opened in 1963 as a dug-in port. The Yufutsu Plain spreads to the east, and low land of peat and sand continues to the coastline. On a coast with no bay into which large ships could be brought, the construction method of digging was chosen.

In the 1961-69 photograph, the scarcity of water surface catches the eye first. Most of the frame is pale-colored wild land and farmland-like lots, with straight land divisions and stripe-like streaks lined up. Water appears only at the southern end. A rounded water surface connects through a thin neck to an angular, wide water surface, and from there a straight channel runs south and out to the sea. Short jetties stick out on the left and right of the mouth. This can be read as the stage at which the digging began from the side near the sea and had not yet reached inland.

If you step to 1974-78, a large dark blue-green water surface opens in the center, which was wild land. Its edges are enclosed by angular quays, and the farmland-like stripes are cut off by those lines. On a black flat area on the north shore, many rows of long, narrow piles line up, and a curved band wraps around them. To the northeast, reddish-brown square lots and a row of white round tanks appear, and on the west shore long buildings with green roofs form a row.

In the photograph as of 2026, the pier projecting to the north of the anchorage has become a wide paved flat area, and long white-gray transit sheds and rows of white vehicles line up. The black flat area that occupied the north shore in 1974-78 has changed into paving and green, and the black piles have moved to the east shore. Even so, the straight channel that ran out to the sea in the oldest photograph and the mouth of the port as of 2026 are at almost the same position in the frame. The direction of the channel does not move.

Toyama Shinko, which turned the water of a lagoon into a port

On the inner side of a sandbar opening toward Toyama Bay there was a lagoon called the Hojozu Lagoon. It was terrain in which a band of sand and gravel carried by rivers, piled up long and narrow, separated the water surface from the open sea. By digging down, deep water could be secured, and the sandbar blocked the swells of the open ocean. In that the water surface to be dug was there first, its premise differs from that of the other dug-in ports. It opened in 1968.

The 1961-69 photograph is black and white, and the dark sea surface of Toyama Bay takes up almost the whole upper half. From the center downward a large dark water surface spreads sideways, and this is the lagoon. Between the lagoon and the sea a sandbar extends diagonally from the lower left to the upper right, rows of houses continue densely along its ridge, and one straight line passes from end to end. Toward the east of the sandbar, there is only a thin dark band running vertically that cuts through the sandbar.

In 1974-78, that whole area toward the east has been cut through, and a wide channel connects the lagoon and the open sea. It is the mouth of the port. On both sides of the cut the rows of houses remain as they were, and the line that ran along the ridge of the sandbar becomes a dead end on the east and on the west. On the sea surface north of the sandbar, thin white lines enclose a large rectangle. The inside of the enclosure is still water, which can be read as the stage at which only the seawalls had been drawn first.

In the photograph as of 2026, the inside of that enclosure has become land, where bands of lawn and trees, a ring road, and a semicircular plaza are placed, and boats with sails are moored at the water's edge. A bridge with cables stretched in a fan from two main towers spans high over the mouth of the port. It is the Shinminato Ohashi Bridge, opened in 2012. The two banks that were cut apart had long been linked by a ferry run by the prefecture. If you move your eyes to the left edge, a thin channel that looks like the Uchi River and the dense rows of houses edging it remain at almost the same position as in the oldest era.

Tagonoura, dug out by a papermaking town

At the head of Suruga Bay, on a straight beach where sand and gravel carried by the Fuji River piled up, lies Tagonoura Port. Paper mills gathered behind it, and large amounts of raw materials and fuel had to be brought in. On a beach with neither cape nor inlet, the method chosen was to dig down behind the beach. It was opened as a dug-in port in the early 1960s.

In the coarse black and white of 1961-69, a long, narrow dark water surface lies on the inner side of the beach, and the mouth leading to the open sea is narrowly pinched. By 1974-78 the water surface has been put in order into the shape of a triangular anchorage, and the edges have switched to straight seawalls. The 1979-83 photograph is dark overall, and the water inside the port sinks especially black. On the jetty, white cylindrical tanks form a row, and the lower right corner is missing, with no photograph. In 1987-90 the water inside the port brightens to blue-green, and offshore white rectangles line up at equal intervals. As of 2026 the water surface stretches branches in three directions, and on the east side lawns and garden paths and a large building with a red roof have been placed.

Sendai Port, where water was brought in behind the beach

Sendai Port (Sendai Shinko) was placed a little more than 10 km east of the town area of Sendai, on low land where a long beach of sand carried by the Natori River and the Nanakita River lies alongside the thin water surface of the Teizan Canal, opened in the Edo period. Because this location can be traced back to 1945-50, you can see the appearance before the digging from a point one step older than at the other ports.

In that oldest photograph, the coastline runs diagonally, and a black band of pines continues on the inner side. The land side is filled with paddies and fields in strips, and below the center a long, narrow water surface extends parallel to the coast, its end bending into a hook shape. The triangle at the lower right has not been photographed. Even if you step to 1961-69, this composition hardly moves. The change of bringing water in behind the beach appears all at once in the next era. In 1974-78 a wide water surface cuts diagonally through the center of the frame, and tanks with round roofs line up at the upper right. The port opened in 1971. By 1984-86 the straight lines of piers have been added to both banks of the channel, and two ships are drawing wakes. On the south side a sandy beach still remains.

As of 2026, red and blue containers and long-legged cranes line up on the southwest shore, and long warehouses and white ship hulls appear in the northwest. In the southwest corner a dark water surface, grassland, and a white sandy beach continue, on the side the digging did not reach. In the Great East Japan Earthquake of 2011, the tsunami reached this coast.

Dig in, or build outward

Even among industrial ports of the same kind, the shape of the edges in the photographs shows from which direction the water surface was gained. Onahama Port is a port on the inner side of a sandy coast drawing an arc. In the 1961-69 photograph the lower half of the frame is all sea, and white streaks of breaking waves run parallel to the shore. There is only one square reclaimed surface, toward the right, and to the north rows of houses with black roofs gather densely, with roads extending radially. The left half is fields in strips. In 1974-78 four piers like the teeth of a comb project toward the sea, with long, narrow water surfaces between them. The sandy beach has been replaced by straight seawalls, and along the shore bundles of dozens of tracks line up. Rather than digging into the land to gain a water surface, this is a form that pushes the land out into the sea to enclose a water surface. As of 2026 the four piers are still at the same positions, and the bundles of tracks have disappeared and changed into large roofs with fine stripes. A building with a round roof and green planting have entered the central pier, and the breakwater offshore has been extended further.

Hachinohe Port Coastal Industrial Zone is low land opening at the mouths of the Mabechi River and the Niida River. In the coarse-grained black and white of 1961-69, the upper half is sea with streaks of waves, and the upper right is blank white as outside the range. A bright surface of sand extends southeast in an arc, and the river mouth is narrow, coming out to the sea by curving around a sandbar. There is only one thin breakwater going out offshore, and the lower half is a dense town area. In 1974-78 the arc of sand has disappeared and changed into a bright surface with edges cut in straight lines, where several dozen round tanks line up. The white breakwater offshore makes corner after corner, and its gaps are the entrances for ships. To the southeast, comb-tooth-shaped piers are added. As of 2026 a large L-shaped pier goes out offshore from the center, and on a separate surface to the east two large white round tanks and a long landing pier appear. In the northwest there is a wide blackish-brown surface and long dark buildings, and one bridge crosses from the south. Even so, only the direction in which the rivers come out to the sea is the same as in the oldest era.

Water surfaces lined up on land a few meters high

The land where digging in worked is low and flat everywhere. If you line up the values at the five measuring points, that flatness shows in the numbers. Only the Kashima Coastal Industrial Zone lines up at around 8 m, and you can read the traces of grading that cut down the original ups and downs and matched them to one height. At the other ports the center value falls between around 1 m and 4 m, and the differences by direction are also from several tens of centimeters to a few meters. When a direction's point falls on water, no value can be obtained, so the table states this.

The value of 9.3 m in the south of Tagonoura Port comes out because the point falls on the side of a slope pressing on Suruga Bay. The hazard map that each city publishes shows as an area how far a storm surge or tsunami is assumed to reach. You can read only the shape of the terrain from the aerial photographs, and the lines of the assumptions are on the side of the maps.

Prices set around the ports

On the port grounds themselves, reference points for the official land prices (Chika Koji) are often not placed. The ones listed in the table are residential and business land several hundred meters to about 3 km from the ports, and the prices are values per square meter. Because the year the record begins differs by location, a comparison lining them up side by side in the same year cannot be made. You can read in which direction the first year and the 2026 publication part from each other at each reference point.

At the reference points of Sendai Port and Onahama Port, the 2026 publication is higher than the start of the record. The reference point of Hachinohe Port, after reaching 54,400 yen from 1999 to 2002, has 2026 as the lowest value in the record up to the 2026 publication. At the reference point of Tagonoura Port too, 2026 is the lowest value up to the 2026 publication. These are to be read not as values of the surfaces where port facilities are placed but as values of the land around them where people live and run businesses.

Points to see when moving back and forth between eras

When you check a dug-in port in the photographs, there are three clues. The first is the direction in which the water surface extends. The shores of reclamation head offshore, and the water surfaces of digging in head toward the land. The second is the straight lines of the edges. The banks of a channel dug through have sharp corners, and curves such as the arc of a sandy beach or the sandbar of a river mouth are cut off partway. The third is the parts that were not dug. The pond and grassland remaining in the southwest corner of Sendai Port, and the thin channel and rows of houses remaining at the left edge of Toyama Shinko, are shapes that were there before the change. The way of reading in which the shapes that remained tell the earlier history can be tried just by switching eras.

The prices in this article are actual examples at each point in time and do not reflect market prices after the article was written.