March Work Report and Site Conditions

(English follows Japanese)

[Sekine River March Regular Work]

It had been a while since we worked in the river, but we continued the work of creating 'shigara' (wattle) soil retaining structures in areas where the soil on the slope along the promenade was washing away significantly.

The vegetation on the slope is dominated by bamboo grass and aucuba, which are common in wasteland areas, perhaps because the tall trees have not been pruned and the lower and middle layers are dark and somewhat dry.

First, we pruned the aucuba in areas where a lot of mud and fallen leaves from the slope were flowing into the river. Then, at the edge of the slope and the promenade (the so-called 'slope transition point') and at several spots on the slope, we used thin bamboo from bamboo forest maintenance instead of stakes, created 'shigara' soil retaining structures using fallen branches and leaves, and inserted the pruned aucuba branches and leaves.

To prevent mud and fallen leaves from being pulled down from above during heavy rain and flowing into the pond, where they accumulate and turn into sludge, we performed this work to fulfill the role of
'not completely stopping or blocking, but allowing the branches and leaves to filter the mud while slowly letting rainwater infiltrate into the soil'
. To do this 100% according to the model requires a lot of materials, time, and manpower, and since the range we can cover doesn't expand easily, we are proceeding with emergency measures starting from the areas where the collapse is most severe, while making various compromises at 20% or 50%.

[Shonan International Village Retarding Basin]

The regular work in March at the retarding basin located in the middle reaches of the river was canceled due to rain, but in the slope area where there was no undergrowth at all during the soil retaining workshop in February, undergrowth has started to grow now that it is spring. The surrounding Yoshino cherry and Oshima cherry trees are in full bloom, surrounded by the voices of birds including the Japanese bush warbler, and the trees surviving on the slope are beginning to sprout new buds.

So that these surviving trees can grow more vibrantly. So that we can increase the undergrowth on the dry slopes where soil washes away easily with rain and wind, and turn them into stable soil.

Inside the pond, invasive aquatic plants are growing thick and dead reeds are left as they are, so I would like to take them out as much as possible, purify the water here even a little before it flows downstream, and transform this into a place that fosters various lives by increasing the biodiversity of aquatic organisms, insects, birds, and butterflies.

The regular work in April at the retarding basin is on the 12th (Sat) from 13:00.
For those who would like to participate in the work, advance reservation is required, so please contact us by email below by the evening of the 11th.
email: chottojapan@icloud.com

* Work in the river is conducted privately with those who have experience participating in 'Earth Regeneration,' 'Chikyumori,' or 'Masako Sakata's workshops,' are familiar with 'shigara soil retaining' and 'water vein' creation work, and have the necessary tools for this work, so if you do not have experience with this kind of work, please first participate in the work at the retarding basin. If you are eligible, please contact us via the email above and we will guide you to the work schedule.

(Mariko Miki / Representative of Mizu no Wa Tsunagi chotto)

[March-Work Report]

It had been a little while since our last work by the creek, but we continued applying the “shigara-dodome” (traditional branch-based erosion control) on the slopes along the creek, where soil erosion has been observed.

The vegetation on these slopes consists mostly of dense overgrown tall trees, which haven’t been pruned, making the mid-to-lower layers dark and somewhat either too wet or too dry.
As a result, common plants found in neglected areas—mainly "sasa" (dwarf bamboo) and "Aoki", Aucuba (Aucuba japonica)—have taken over the area.

We began by pruning the overgrown Aucuba where mud and fallen leaves were heavily flowing into the creek from the slope.
At the boundary between the slope and the pathway—known as the "slope transition point"—and in several locations on the slope itself, we made several "shigara-dodome" retaining fences, using thin bamboo leftover from bamboo grove maintenance work, fallen branches and leaves, and inserted pruned Aucuba branches into them.

This effort is not meant to completely block or dam the flow, but rather to allow the branches and leaves to act as natural filters for the mud, slowing down the rainwater and allowing it to gradually soak into the soil. This helps prevent mud and leaves from being washed directly into the creek during heavy rain, where they would otherwise accumulate and turn into sludge in the creek, the effects of which end up in the sea.

[Shonan Village Reservoir]

Although the regular March work session at the midstream retention pond had to be canceled due to rain, now we see signs of spring on the slope where there had been no undergrowth at all during February’s erosion control workshop. Now, fresh undergrowth has started to sprout.

The cherry trees around the area are in full bloom, and birds, including bush warblers, are singing all around. Trees that have managed to survive on the slope are beginning to sprout new buds.

We want to help these surviving trees grow more vibrantly by increasing the undergrowth on these dry, easily eroded slopes; we hope to transform the area into a more stable, rooted soil environment.

Inside the pond, invasive aquatic plants have spread, and the cut reeds remain where they fell. We aim to remove as many of them as possible to promote water purification before it flows downstream.
By doing this, we hope to increase biodiversity—encouraging aquatic life, insects, birds, butterflies, and more—turning this area into a habitat that nurtures a wide variety of life.

Our next regular maintenance session at the retention pond in Shonan Village in Yokosuka City, Kanagawa Prefecture will be held on Saturday, April 12th at 1:00 PM.

If you are interested in volunteering with us, advance registration is required, so please email us by the evening of April 11th so that we can provide you with information such as the meeting point, what to bring, etc.
(Due to the steepness of the slope where the work is carried out and the presence of the pond, participation is limited to junior high school students and older for safety reasons)
* email: chottojapan@icloud.com

(Text: Mariko Miki)

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