**3. Eco-DRR in Japan**

Ecosystem-based disaster risk reduction (Eco-DRR) is a relatively new concept to reduce the risk of being exposed to natural hazards by avoiding development in disaster-prone areas or by using natural systems as a way to buffer the worst impacts of natural hazards, maintain the resilience of natural ecosystems and their ecosystem services, and help people and communities adapt to changing conditions [14, 15]. The core thinking of Eco-DRR is based on the realization that disasters cause massive damage to the environment, while degraded environments exacerbate disaster impacts and responding to disasters often leads to additional environmental impacts. Well-managed ecosystems, such as wetlands, forests, and

coastal systems, act as natural infrastructure, reducing physical exposure to many hazards and increasing socioeconomic resilience of people. For example, mangroves and seagrass beds can dissipate the destructive energy of storm surge and Tsunami and prevent coastal erosion while supporting fishing and tourism activities and storing high amounts of carbon. Therefore, Eco-DRR is also aimed at reducing the vulnerability of society and establishing disaster-resilient communities.

Japan has a tradition of using ecosystems for disaster mitigation such as maintaining forests to prevent soil erosion, planting trees along its coast to reduce wind-related disasters, and utilizing paddy fields to store flood waters temporarily. Since 2012, Eco-DRR has been incorporated into national policies and planning of the Japanese government. The Basic Act for National resilience, enacted in 2013, is aimed at taking advantage of regional ecosystem-based functions to prevent and reduce disasters. Following this Act, Fundamental Plan for National Resilience was established to promote the use of ecosystem-based disaster reduction approaches and assessment of functions of Eco-DRR initiatives provided during nondisaster times. The National Spatial Strategy and the National Land Use Plan, approved in 2015, also called for the promotion of disaster management using natural ecosystems. Furthermore, Japan's Forest Law requires that Disaster Risk Management (DRM) forests should be planted along the coast to prevent damages from blown sand and salt, high tides, and tsunamis. Under such strong policy drivers, a question is "does it work?"

On March 11, 2011, the Great East Japan Earthquake occurred and trigged a major Tsunami. Consequently, the Tohoku area of Japan was so badly hit Tsunami. In total, this disaster caused more than 15,000 deaths, 2800 missing, and approximately 300,000 people being evacuated [16]. Among the disaster-stricken areas, Miyagi Prefecture suffered the most in terms of fatalities and infrastructure damage. Before the disaster, there were 200- to 400-m-wide pine forests along the Sendai Plains of Miyagi Prefecture having protected the area for the past four centuries. Nevertheless, the forest failed to stop the intrusion of the Tsunami. The coastline of Rikuzentakata City, Iwate Prefecture, was also very famous for its 2-km-long and 200-m-wide pine trees as shown in **Figure 8**. Again, the forest was completely destroyed except for one tree after the 3/11 Tsunami. There is no doubt that the forest along the coast of Tohoku region did reduce the energy of Tsunami. Although the forest was destroyed during the disaster, without it, fatalities and property damage would undoubtedly have been much greater. The question is how to quantify its effectiveness in relation to Tsunami height. It is not difficult to imagine that a coastal forest is effective to a Tsunami with low wave height. The information needed is the threshold of wave height above which a coast forest may fail to dissipate the energy of Tsunamis significantly. Koshimizu [17] pointed out that coastal forests could be rendered useless by liquefaction, but no countermeasures had been discussed. Besides, it should not be forgotten that a fallen tree being moved by a Tsunami can kill people and damage houses.

An interesting phenomenon was observed in Ishinomaki City, Iwate Prefecture. Along a portion of the Watanoha coast, the levee was lightly damaged, but the residential area behind was devastated as can be clearly seen in **Figure 9**. The levee height before the disaster was 4 m, and the Tsunami height in Ishinomaki was more than 8.6 m according to Japan Meteorology Agency. This implies that the Tsunami overtopped the levee without much energy dissipation. Otherwise, the levee would have been badly damaged. The same phenomenon may also apply to coastal forests if the height of a Tsunami is much higher than the height of the forest. After the disaster, the Japanese Government decided to invest ¥59 billion to restore 3660 hectares of trees in Tohoku, which were destroyed by the Tsunami [18]. However, as can be seen from Google Earth, the restoration of coastal forests has not produced

**13**

*New Frontiers in Flood Risk Management DOI: http://dx.doi.org/10.5772/intechopen.81925*

*Coast forest before and after the Tsunami disaster on March 11, 2011.*

**Figure 8.**

**Figure 9.**

any visible progress. Instead of costal forest, concrete levee is expanding along the coast as shown in **Figure 10**. This was also confirmed by author's field survey conducted in July 2018. Despite legislative development with regard to Eco-DRR in Japan, the implementation appears not straightforward. A multilayered defense system combining Eco-DRR measures with conventional concrete-based measures

Another case, which has been advocated as an example of Eco-DRR, is the Kabukuri-numa wetland in Osaki City, Miyagi Prefecture, Japan. In the 1970s, it was merely used as a flood-retarding basin. Large-scale dredging of the wetland was planned to increase its flood regulation capacity in 1996. However, in response to environmental concerns, the dredging plan was withdrawn. Instead, the area of the Kabukuri-numa wetland was expanded by transforming surrounding fallow farmland to wetland to meet the flood regulation demand. Furthermore, water was retained in surrounding paddies during the winter so as to function as seminatural, but still important, habitat for wetland-dependent wildlife. In 2005, the Kabukuri-numa wetland and surrounding paddy fields were registered together as a Ramsar wetland site [19, 20]. As a result of this wetland expansion, a large number of waterfowls overwinter in Kabukuri-numa, eating fallen grain and weeds in the

may deserve serious discussion or even debate.

*Devastated residential area behind a coastal levee.*

*Recent Advances in Flood Risk Management*

is "does it work?"

coastal systems, act as natural infrastructure, reducing physical exposure to many hazards and increasing socioeconomic resilience of people. For example, mangroves and seagrass beds can dissipate the destructive energy of storm surge and Tsunami and prevent coastal erosion while supporting fishing and tourism activities and storing high amounts of carbon. Therefore, Eco-DRR is also aimed at reducing the

Japan has a tradition of using ecosystems for disaster mitigation such as maintaining forests to prevent soil erosion, planting trees along its coast to reduce wind-related disasters, and utilizing paddy fields to store flood waters temporarily. Since 2012, Eco-DRR has been incorporated into national policies and planning of the Japanese government. The Basic Act for National resilience, enacted in 2013, is aimed at taking advantage of regional ecosystem-based functions to prevent and reduce disasters. Following this Act, Fundamental Plan for National Resilience was established to promote the use of ecosystem-based disaster reduction approaches and assessment of functions of Eco-DRR initiatives provided during nondisaster times. The National Spatial Strategy and the National Land Use Plan, approved in 2015, also called for the promotion of disaster management using natural ecosystems. Furthermore, Japan's Forest Law requires that Disaster Risk Management (DRM) forests should be planted along the coast to prevent damages from blown sand and salt, high tides, and tsunamis. Under such strong policy drivers, a question

On March 11, 2011, the Great East Japan Earthquake occurred and trigged a major Tsunami. Consequently, the Tohoku area of Japan was so badly hit Tsunami. In total, this disaster caused more than 15,000 deaths, 2800 missing, and approximately 300,000 people being evacuated [16]. Among the disaster-stricken areas, Miyagi Prefecture suffered the most in terms of fatalities and infrastructure damage. Before the disaster, there were 200- to 400-m-wide pine forests along the Sendai Plains of Miyagi Prefecture having protected the area for the past four centuries. Nevertheless, the forest failed to stop the intrusion of the Tsunami. The coastline of Rikuzentakata City, Iwate Prefecture, was also very famous for its 2-km-long and 200-m-wide pine trees as shown in **Figure 8**. Again, the forest was completely destroyed except for one tree after the 3/11 Tsunami. There is no doubt that the forest along the coast of Tohoku region did reduce the energy of Tsunami. Although the forest was destroyed during the disaster, without it, fatalities and property damage would undoubtedly have been much greater. The question is how to quantify its effectiveness in relation to Tsunami height. It is not difficult to imagine that a coastal forest is effective to a Tsunami with low wave height. The information needed is the threshold of wave height above which a coast forest may fail to dissipate the energy of Tsunamis significantly. Koshimizu [17] pointed out that coastal forests could be rendered useless by liquefaction, but no countermeasures had been discussed. Besides, it should not be forgotten that a fallen tree being

An interesting phenomenon was observed in Ishinomaki City, Iwate Prefecture.

Along a portion of the Watanoha coast, the levee was lightly damaged, but the residential area behind was devastated as can be clearly seen in **Figure 9**. The levee height before the disaster was 4 m, and the Tsunami height in Ishinomaki was more than 8.6 m according to Japan Meteorology Agency. This implies that the Tsunami overtopped the levee without much energy dissipation. Otherwise, the levee would have been badly damaged. The same phenomenon may also apply to coastal forests if the height of a Tsunami is much higher than the height of the forest. After the disaster, the Japanese Government decided to invest ¥59 billion to restore 3660 hectares of trees in Tohoku, which were destroyed by the Tsunami [18]. However, as can be seen from Google Earth, the restoration of coastal forests has not produced

moved by a Tsunami can kill people and damage houses.

vulnerability of society and establishing disaster-resilient communities.

**12**

**Figure 8.** *Coast forest before and after the Tsunami disaster on March 11, 2011.*

#### **Figure 9.**

*Devastated residential area behind a coastal levee.*

any visible progress. Instead of costal forest, concrete levee is expanding along the coast as shown in **Figure 10**. This was also confirmed by author's field survey conducted in July 2018. Despite legislative development with regard to Eco-DRR in Japan, the implementation appears not straightforward. A multilayered defense system combining Eco-DRR measures with conventional concrete-based measures may deserve serious discussion or even debate.

Another case, which has been advocated as an example of Eco-DRR, is the Kabukuri-numa wetland in Osaki City, Miyagi Prefecture, Japan. In the 1970s, it was merely used as a flood-retarding basin. Large-scale dredging of the wetland was planned to increase its flood regulation capacity in 1996. However, in response to environmental concerns, the dredging plan was withdrawn. Instead, the area of the Kabukuri-numa wetland was expanded by transforming surrounding fallow farmland to wetland to meet the flood regulation demand. Furthermore, water was retained in surrounding paddies during the winter so as to function as seminatural, but still important, habitat for wetland-dependent wildlife. In 2005, the Kabukuri-numa wetland and surrounding paddy fields were registered together as a Ramsar wetland site [19, 20]. As a result of this wetland expansion, a large number of waterfowls overwinter in Kabukuri-numa, eating fallen grain and weeds in the

**Figure 10.** *Current situation of defense construction along the Tsunami-hit coast.*

flooded paddy fields. The bird droppings, which are rich in phosphate, function as high-quality natural fertilizers for rice and enrich the soil. Rice cultivated under such an environment is branded as such and can be sold at a higher-than-average price. In addition, the large number of overwintering birds attracts a large number of tourists every winter. Although the ecosystem services of the Kabukuri-numa wetland during nondisaster times have been well demonstrated, its flood regulation capability has not been tested since there have been no large-scale floods in recent decades. In addition, there are concerns over the water quality of the wetland due to the large number and high concentration of birds. Bird droppings entering paddy fields may contribute to rice production but may also impact the water quality of adjacent wetlands if entering into its water body. As a matter of fact, water quality testing in the Kabukuri-numa wetland by the author of this chapter indicated that the water body is already eutrophic. How to make this Eco-DRR initiative sustainable is a question to be answered.
