Disaster prevention forest - bosairin

An artificial forest created to prevent and reduce damage to residential areas, roads, farmland, etc. from disasters caused by natural phenomena or human factors. They may be created by private individuals, but they are often designated as conservation forests based on the public interest functions stipulated in the Forest Law. Of the various types of conservation forests, the following 11 types qualify as disaster prevention forests created for the purpose of preventing disasters. (1) Conservation forests for preventing landslides (preventing landslides and erosion with tree roots and fallen leaves). (2) Conservation forests for preventing landslides (preventing the collapse of unstable ground). (3) Conservation forests for preventing blowing sand (preventing blowing sand). (4) Conservation forests for preventing wind damage (preventing damage from strong winds). (5) Conservation forests for preventing flooding of rivers and mitigating water pressure. (6) Conservation forests for preventing tide damage (preventing damage from tsunamis and high tides). (7) Conservation forests for preventing snowstorms (protecting roads and railways from snowstorms). (8) Fog prevention forests (protecting farmland from sea fog). (9) Avalanche prevention forests (preventing avalanches and providing a buffer zone when avalanches occur). (10) Rockfall prevention forests (reducing the danger of falling rocks). (11) Fire prevention forests (preventing the spread of fires by using flammable tree species).

In addition to such protective forests, other types of disaster prevention forests can also be considered Satoyama disaster prevention forests, which are used to prevent mountain disasters near settlements, and wildlife cultivation forests, which are maintained in forests separate from human habitations in order to prevent damage to crops by wild animals.

In the Great East Japan Earthquake in March 2011, coastal disaster prevention forests, which had protected seaside communities from blown sand, salt damage, strong winds, and high tides, suffered devastating damage. The damage extended to approximately 3,700 hectares along the coast from Aomori Prefecture to Chiba Prefecture, but it has become clear that the forests have a disaster mitigating effect, such as mitigating the power of tsunamis and preventing drifting debris from the sea from entering the land. The Forestry Agency is currently working to redevelop 140 kilometers of coastal disaster prevention forests in the affected areas that were damaged by being washed away, submerged, or collapsed.

[Editorial Department]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

自然現象や人為的な原因で起こる災害から、宅地や道路、農地などの被害を防止、軽減するためにつくられた人工の森林。民間や個人で設ける場合もあるが、森林法に定められた公益的機能に基づく保安林として指定されていることが多い。各種の保安林のうち、以下の11種類が、災害を防止する目的で設けられた防災林に該当する。(1)土砂流出防備保安林（樹木の根や落ち葉によって土砂の流出や侵食を防ぐ）。(2)土砂崩壊防備保安林（不安定な地盤の崩壊の防止）。(3)飛砂防備保安林（飛砂の防止）。(4)防風保安林（強風による被害を防ぐ）。(5)水害防備保安林（河川の氾濫(はんらん)の防止や水勢の緩和）。(6)潮害防備保安林（津波や高潮による被害の防止）。(7)防雪保安林（吹雪(ふぶき)から道路や鉄道を守る）。(8)防霧保安林（耕地を海霧から守る）。(9)なだれ防止保安林（なだれの発生を防ぎ、発生時には緩衝帯となる）。(10)落石防止保安林（落石による危険を抑制する）。(11)防火保安林（燃えにくい樹種により火災の延焼を防ぐ）。

　このような保安林以外に、集落付近の山地災害を防止する里山防災林、野生動物による農作物被害を防ぐため、人とすみ分ける地域の森林を整備する野生動物育成林なども防災林の一つといえる。

　2011年（平成23）3月の東日本大震災では、海に近い集落を飛砂や塩害、強風、高潮などから守ってきた海岸防災林が壊滅的な被害を受けた。その被害は青森県から千葉県に至る海岸沿いに約3700ヘクタールにも及んだが、一方で、津波の威力を緩和し、海上の漂流物が地上へ侵入することを防ぐなどといった減災効果が明らかになった。林野庁では、流出や水没、倒伏などで損なわれた被災地の140キロメートルに及ぶ海岸防災林の再整備を進めている。

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