#edo river

Tokyo Bay (Japan, July 2014) from Sentinel-1A.

The centre of Tokyo lies mostly south of the Arakawa River, the middle of the three main rivers shown in this photograph.  To is left is the Tama River, and to its right is the Edo River.  All three flow into Tokyo Bay.  At the mouth of the Tama are the runways of Haneda Airport.

Northwest of Tokyo Bay, the bright radar reflections show dense construction.  Southeast of the bay is Minami-Bōsō Quasi-National Park, with an overall brownish colour.

The leaves tread softly Right from the banks to the stream As the wind comes by   Dew touches my skin Seeing the river run slow To go heap the earth   A strong gust then sweeps Whispering to the river And being pulled through   Calm thou was the hut As rain pours and winds take route Here at winter day

江戸東京の大河川 Edo-Tōkyō no Taikasen (Rivers of Edo-Tōkyō)

Paleolithic inlets and outlets during the Jomon Period. This is essentially Edo and its suburbs. Understanding the topography of Tokyo is critical to understanding the history of Edo and her earlier, less famous history. By the way, click to enlarge.

We’ve Reached a Milestone!

This is the 200th article of JapanThis!I never thought I’d make…

A research team in Kinki University surveyed the riverbeds of the Edo and Tone rivers which run into the Tokyo bay to study the movement of the radioactive cesium originated from the Fukushima Daiichi nuclear power plant accident this April. They sampled the mud layer about 20cm below the riverbed from five different locations, and measured the amount of cesium.

The team learned that the radioactive cesium from the accident has been accumulating in much lower layer of riverbeds than the 5cm-below-surface layer. 

In the Edo river area about 15km from the estuary (the place river meets the ocean) where roughly 53,000 bq/㎡ of cesium was detected at the time of the accident, 56% of the cesium was accumulating in the lower layer of riverbed below the 5cm layer.

In other four locations of the Tone river, 47~78% of the cesium was also accumulating in the lower layers than the 5cm layers.

The monitoring of the radioactive cesium conducted by the environmental ministry in much of the Tohoku and the Kanto rivers since May 2011 is limited to the samples taken from the layers that are around 5cm below the surfaces of the riverbeds. Prof. Hideo Yamazaki of the Kinki Univ. research team says, "Typhoons can move the radioactive cesium in the 20cm-below-surface layers into the Tokyo bay rather easily. The government should quickly adjust the monitoring methods to more accurately measure the distribution of the cesium in riverbeds to predict the effect on fish in the Tokyo bay."