Introduction |
Forests help protect people and their assets from natural
hazards, including floods, debris flows, landslides,
rockfalls, snow avalanches, snowdrifts, and high winds, in
two main ways—directly by reducing meteorological and
hydrogeomorphic forces that affect people, structures, and
utility corridors; and indirectly by reducing soil erosion or
improving watershed conditions and air quality. Both types
of protection are more attractive than artificial structures for
episodic natural hazards due to their relatively low costs and
environmental friendliness. |
Development of Railway Protection Forests |
Railway protection forests are classified into nine categories, depending on their function: snowdrift, snow avalanche, sand drift, landslide, rock fall, flood, fire, wind, and natural springs. Each is explained below. |
Snowdrift protection forests |
About 90% of all railway protection forests in Japan are for
snowdrift protection. They are mainly on Hokkaido and the
northern part of Honshu. The most common species used
in these forests is Japanese Cedar (Cryptomeria japonica)
in Honshu and Norway Spruce (Picea abies) in Hokkaido
(photographs). |
Snow avalanche protection forests |
The need to maintain forests on slopes susceptible to
avalanches has long been known in Japan. This knowledge
was integrated into the legal system and was also part of
forest management practice in Japan; some feudal landlords
designated part of their lands as snow avalanche protection
forests, where neither cutting nor thinning was allowed. |
Photo: Snowdrift protection forest on Soya Line in Hokkaido (Author) Photo: Snowdrift protection forest on Uetsu Line in Honshu (Author) Photo: Snow avalanche protection forests on Joetsu Line in Honshu (Yosuke Masui) |
in 1914 experienced 75 avalanches in 1917, some causing
deaths and injuries as well as serious property losses. As
the result of lessons learned, the Railway Agency designated
slopes prone to avalanches as snow avalanche protection
forest areas and carried out necessary forestation. The
Ganetsu Line was affected by some 250 avalanches in its
first 20 years, but experienced only seven in the second 20
years after the trees reached maturity. |
Sand drift protection forests |
The Sea-of-Japan Honshu coast has many areas with extensive sand dunes and trains on new lines passing through these areas encountered frequent problems such as derailments and blockages due to sand drifts on tracks. The first trackside wooden fences built to block sand drifts were easily destroyed by gales and proved ineffective. As a result, sand drift protection forests based on traditional forestry methods were used as an alternative measure and planted along the Uetsu Line in 1921. Aeolian movement of sand stops completely as soon as sand dunes are revegetated, and the protective effects of sand drift protection forests are immediate and significant. Sand drift protection forests have also been established on the Hokuriku, San’in and other coastal lines. |
Landslide and rockfall protection forests |
Landslides, debris flows and rock falls are frequent natural
hazards for railways in Japan’s mountainous regions, where
the ground is weak and precipitation high. As more tracks
were built in cuttings through mountainous regions, more
landslides, debris flows and rockfalls occurred, prompting
railways to develop landslide and rockfall protection forests,
which are now widespread across Japan. |
Table 1: Lower Bouond ACSD (δ) by Forest Type |
Other railway protection forests |
For more than 100 years, the Japanese rail network has used the benefits of forests in many situations. Protection forests surrounding springs secured the water supply for steam locomotives, stations, offices, huts, and quarters before it was possible to pipe water in. Fire protection forests with firebreaks are also a remnant of the steam age. Where tracks are exposed to extreme gales or floods, wind protection forests and flood protection forests have been planted. |
Forestation Methods and Silviculture Systems |
The forestation and silviculture systems used for railway
protection forests are selected and adjusted to fit local
conditions and functional needs. For example, snowdrift
protection forests in Honshu are planted with Japanese
Cedar, and with Norway Spruce in Hokkaido. Both species
are evergreen, fast growing, and tolerate high densities;
effective snowdrift protection is provided by a strip just 20-m
wide. |
Challenges and Perspectives |
For more than 100 years, the principle of railway protection
forests has been founded upon silviculture of monocultures,
enabling maximum timber yield and revenue at cutting.
In the past, railway protection forests provided timber for
railway sleepers, buildings and other structures. Sale of
these products provided the revenue needed for silviculture
treatments. |
Table 2: Upper Bound Yield Ratio (ρ) by Tree Species |
Makoto Shimamura Dr Makoto Shimamura is Director of the Disaster Prevention Research Laboratory at the Research and Development Center of the JR East Group. He joined JNR in 1978 and transferred to JR East in 1987. During his 30-year career in both organizations, he has worked to preserve and enhance railway protection forests. He received his doctorate from the University of Tokyo in 2008. |