Walking along the Sumida River | Discover the Iwafuchi Reference Point! | Iwabuchi Water Gate - Toshima Bridge


The elevation of Japan is based on the mean sea level of Tokyo Bay, T.P. (Tokyo Peil). The water mark for measuring the mean sea level is located at the Reigishijima Water Level Observatory near the mouth of the Sumida River (formerly called the Arakawa River), and its zero level is named A.P. (Arakawa Peil). In other words, the Sumida River and the Arakawa River have played a leading role in Japan’s elevation world. And yet, when the Arakawa River is under construction, it is the Iwabuchi Reference Point that is used as the height standard. I wonder why they don’t just say that the A.P. is the standard.

Found the Iwabuchi reference point!

The Sumida River branches off from the Arakawa River. I got off at Akabane Station to walk from the junction.


Ai-chan (Akabane Ichibangai Shopping Street mascot character)

As I headed north to cross the Shinkashigawa upstream of the Sumida River on Route 122, I had to walk along the first street. As I looked up to suppress the temptation to enter all the attractive stores, I spotted Ai-chan, a loose character. I immediately recognized it as the mascot of Akabane, as it had a red feather growing out of it. I wondered if the white feathers of SOEY’s mascot below it were to prevent the characters from covering each other.


Shinkashigawa and Akabane Sakurazutsumi Green Space

Crossing the Shinkashigawa River. To the west is the Akabane Sakurazutsumi Green Space. In about three weeks, the cherry blossoms will be in full bloom. The Arakawa River flows on the other side of the Akabane Sakurazutsumi Green Space.


Arakawa River

I came to the Arakawa River.

What I see in the river is probably a dredging boat. If we don’t deepen the water frequently, we are afraid of flooding.


The old and new Iwabuchi sluice gates

I walked a little further downstream and saw the sluice gate.

The red sluice gate is the old Iwabuchi sluice gate, and the blue one is the Iwabuchi sluice gate.

If you look at them side by side, you can see that they are quite different in height.


Arakawa River Flood Control Museum

At the bottom of the embankment, there is the Arakawa River Flood Control Museum.

I have been here twice before, so I didn’t go inside this time.

The museum displays the achievements and possessions of Mr. Aoyama Akira, the chief engineer of the Arakawa River Downstream Improvement Office. After seeing this exhibit, I came to respect Mr. Aoyama. As you can easily see by looking him up, he is a magnificent person.


Monument commemorating the completion of the Arakawa Spillway

There was a monument commemorating the completion of the Arakawa Spillway. If you were in charge of a large scale civil engineering project, you would probably want your name to be engraved on the monument. However, Mr. Aoyama did not put his name on the monument because he believed that the huge civil engineering work was the result of all the people involved. This kind of action, in fact, enhances one’s fame, doesn’t it?

水準基標 岩淵基準点

Water level reference Iwabuchi reference point

As I strolled further in front of the Arakawa River Flood Control Museum, I found the “Level Base Marker Iwabuchi Reference Point”!

On the side of the pillar, it said, “This reference point is used as a height standard when the Arakawa River is under construction. It also has a height value written on it. I didn’t notice it when I took the photo, so it’s only vaguely visible. If you zoom in the photo to the maximum before reducing the resolution, it looks like it says 8.208m. The relationship between A.P. and the Iwafuchi reference point changes over time, so I wonder if using the Iwafuchi reference point as the height standard rather than A.P. would be a better way to design the embankment in a fail-safe manner? I don’t know, so I guess it’s okay.

Walking along the Sumida River


Old Iwabuchi Sluice Gate

This photo was taken looking back after passing the old Iwafuchi Water Gate. The water flowing into the left foreground is the Sumida River. It’s a beautiful view.

But what is the reason for the slit on the right side of the old sluice gate?

Wouldn’t leaving the old sluice gate open be enough to cover the water flowing into the Sumida River without the slit?

Because sometimes you want to let a large amount of water flow rather than leave it open?

But in such a case, it would cause flooding downstream of the Sumida River, right? I don’t really understand this reason either, so oh well.


Heliport by the Iwabuchi sluice gate

There was a heliport beside the Iwafuchi sluice gate.

I thought heliports were made to be flat so that helicopters could land easily, but they were made to be high in the center and low around the perimeter. Certainly, you don’t want to have a puddle of water when it rains. I wonder if the decks of aircraft carriers are also sloped for drainage purposes.


The letters 20R

The letters “20R” appeared out of nowhere. It seems to be because it is a point 20 km from the sea. I wonder if the R is attached because it is on the right bank.

Recently, I’ve had the opportunity to see large letters that can be read from the sky several times, but they are usually written so that they can be read from the west. Do emergency helicopters come from the west?



A plant suddenly appeared. Why is the piping in these chemical plants so complicated? Can’t they be made simpler? I always wonder. It’s a nice look, though.


Two round buildings

Now two round buildings appeared. They look like a school. I wonder if we can see the planetarium.


Nitta Bridge

I heard that the Sumida River has many different types of bridges. This Nitta Bridge is unusual in the shape of its piers.


Toshima Bridge

We came to the Toshima Bridge.

This is the bridge I crossed six weeks ago when walking along the Shakujii River from its mouth, so I feel a sense of familiarity. Today I decided to walk in the opposite direction and return from the Ohashi Bridge.

Walking data

Course: JR Tohoku Line Akabane Station -> Sumida River -> Tokyo Metropolitan Transportation Bureau Nippori-Toneri Liner Ogi-Ohashi Station
Distance: 9.1km
Time: 2h9m