大楠山系〜相模湾をつなぐ関根川：春の定点観測

プライベートで三浦半島の大楠山系頂上部に造成された湘南国際村から相模湾へと流れる関根川の環境整備ボランティア活動「水の環つなぎ：chotto」を主宰しています。

河川は行政の管理下にあり勝手に何かをすることはできないため、横須賀市にボランティア団体として登録し、ゴミ拾いや遊歩道沿いに落ちている枝の片付けなどの作業をさせて頂いていました。

行政の担当部署の方々がとても協力的で、私たちが、

「遊歩道沿いの斜面地から大雨の際に泥や落ち葉が川へ流れ込んで堆積し、夏の高温時にはヘドロ化して悪臭を放っており、これは川の生態系、しいてはその先の海への影響もあると考えられるので、斜面地にしがら土留めを作る作業をしたいのですが」

と相談させて頂いたところ、当初は私有地と考えられていて作業が認められていなかった斜面地の所有者を調べてくださり、市の管理下であることがわかって作業を認めて頂くことができるようになりました。

続いて中流部に約30年前に湘南国際村の造成に伴ってつくられた遊水池の手入れにも入らせて頂く流れに。

「生物多様性の回復」

がお題目となっているのですが、広さはあるけど資金はゼロ、人手も少人数、という状況なので、優先順位を決めて一歩ずつ進めて行きます。

活動場所の湘南国際村遊水池と関根川沿いの春の様子です。

活動の様子は下記のnoteにまとめていますのでご興味持ってくださる方はぜひご覧いただき、活動のお手伝いをして頂ける方もぜひnoteに記載している連絡先emailへご連絡頂ければうれしいです。

https://note.com/mizunowa_chotto/n/n88c3883bb808

*SNS (Bluesky: https://bsky.app/profile/chotto-river-ocean.bsky.social)

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I privately organize a project called 'chotto: Regenerate ecological connectivity linking land, rivers, and the sea' dedicated to environmental restoration or regeneration along the Sekine River, which flows from the summit area of the Ōgusu mountain range in the Miura Peninsula—where the Shonan Village was developed—down to Sagami Bay.

The name of the project 'chotto' in Japanese means “just a little.”

It reflects an approach not based on the idea that humans can or should control nature, but rather on the belief that humans should make only small care at key points just enough to allow nature to regenerate itself.

Since rivers are managed by the local government and we cannot carry out activities without their permission, we registered our group as an official volunteer organization with the city of Yokosuka.

Since then, we have been engaged in activities such as picking up litter and clearing overgrown grass or branched along the walking trails.

The local government officials we’ve worked with have been very supportive.

For instance, when we consulted them about the following concern:

“During heavy rain, soil and fallen leaves from the slopes along the walking paths wash into the river, where they accumulate and turn into sludge during the hot summer months, creating foul odors. We believe this not only impacts the river’s ecosystem but also affects the downstream marine environment. We’d like to construct natural retaining barriers (shigara-do-dome) on the slopes to prevent this.”

They investigated the ownership of the slopes, which had initially been assumed to be privately owned and therefore off-limits for volunteer work. They found that the land is actually under city management, and thus granted us permission to carry out the work.

Following that, we were also given permission to begin maintenance on a reservoir, retention basin located in the midstream area of the river that was built about 30 years ago during the development of Shonan International Village.

Our guiding principle is “Restoring or regenerating biodiversity”, however the area is large, we have no funding and only a small number of volunteers, so we’re moving forward step by step, focusing on priority tasks.

Photos above have captured the spring along the Sekine River and the retention basin at Shonan Village, where our activities take place.

The details of our activities are reported on another blog platform called 'note', and some of the posts have English translation.

https://note.com/mizunowa_chotto/n/n88c3883bb808

If you're interested, please take a look—and if you're willing to lend a hand, we would be delighted to hear from you via the contact email listed on 'note'.