Facility against tsunamis and green infrastructure—a case study of post-disaster reconstruction after the Great East Japan Earthquake

ABSTRACT

The infrastructure reconstructions after the Great East Japan Earthquake (GEJE) and related attempts on biodiversity conservation were categorized and reviewed. Seawalls and wave-dissipating blocks reconstructed after the GEJE are examples of gray infrastructure. Reconstructed coastal protection forests and constructed green spaces are “green” infrastructure in the sense of using plants; however, they also seriously damage coastal ecosystems. Present states of coastal protection forests and green spaces would not sufficiently provide ecosystem services expected for a coastal environment. Attempts to conserve biodiversity and landscape, i.e., unreconstructing or downsizing seawalls, setting back seawalls, designating conservation areas, and laying coastal sand on seawalls or mounds of coastal protection forests, have been made and established. However, they were not applied with the concept of green infrastructure, were designed not to deliver ecosystem services, and were independently implemented and isolated without a strategically planned network. Therefore, the network of the sites of these attempts should be planned to deliver the expected ecosystem services. Laying coastal sands on facilities is probably useful for building a type of corridor that links isolated conservation areas. Studies on the present state of biodiversity and other environments and sociological studies are needed to improve ecological services from reconstructed coastal area.

KEYWORDS:

• Biodiversity conservation
• coastal protection forest
• green space for disaster prevention
• seawall
• the Great East Japan Earthquake and Tsunami

1. Introduction

In recent years, green infrastructures that harness multiple functions of ecosystems have attracted attention. Concepts of green infrastructure and hybrid approaches combining gray and green infrastructure have been applied to a wide range of infrastructures or ecosystems in either urban or rural areas (Benedict and McMahon 2006; Kambites and Owen 2006; Royal Society 2014; Sutton-Grier, Wowk, and Bamford 2015; Natuhara 2018). Design and management of planned networks of natural and seminatural areas, with environmental features to deliver a wide range of ecosystem services, are the focus of green infrastructures in the European Commission (2013). The United States Environmental Protection Agency (US EPA 2010) treated green infrastructure as a resilient approach using plant or soil systems to manage wet weather impacts on the urban environment. In areas often subjected to natural disasters, green infrastructure has been used as a natural function for facilities against disasters, including ecosystem-based disaster risk reduction (Eco-DRR) programs (Renaud et al. 2016; Faivre et al. 2018). Green and hybrid infrastructures have also been discussed in relation to the functions of natural or seminatural areas against disasters in Japan that is one of the countries that has considerably suffered from natural disasters (Satake 2015; NCB MEJ 2016).

Tsunamis are among natural disasters that cause significant damage to the society, affecting the lives and properties of people (UN DRR 2017). Thus, facilities against tsunamis are important in areas affected by this phenomenon (Renaud and Murti 2013; Sasaki, Tanaka, and Sakamoto 2013; Harbitz et al. 2016). There is scarce academic literature on green infrastructure related to facilities and Eco-DRR for tsunamis, except for several studies concerning the effects of mangroves and other trees in protection from tsunami damages (Wahyunto et al. 2009, Natuhara 2018; Wanger et al. 2020). East Japan is one of the regions that has experienced the highest number of large-scale earthquakes and tsunamis (Suppasri et al. 2013; Satake 2015). The coastlines in the region were relatively well-prepared to protect inland residential areas, rice paddies, and other inland crops before the GEJE. Seawalls for flood tides and tsunamis had been constructed, and coastal forests had been planted and maintained for coastal sand blows, strong winds, and tsunamis (Furuta and Seino 2016; Kurosawa 2016; NCB MEJ 2016). These facilities were more or less considered the functions of ecosystem services, including accessibility to the public, public health by the venue of recreation, educational nature activities, and improving landscape (Furuta and Seino 2016; NCB MEJ 2016).

The Great East Japan Earthquake (GEJE) and following tsunami on March 11, 2011, resulted in significant damage to people’s livelihoods and considerable changes in the surrounding natural environment. After the GEJE, the largest facilities against tsunamis in the world, including seawalls, coastal protection forests, and green spaces, have been reconstructed or newly constructed in damaged areas. Unfortunately, the concepts of green and hybrid infrastructure and Eco-DRR have not been applied in the planning process, regardless of the promotion of these concepts by the Japanese government (Furuta and Seino 2016). Although attempts have been made to revise plans or modify facilities for biodiversity and landscape conservation in many reconstruction sites (Kurosawa 2016), the concepts of green and hybrid infrastructure and Eco-DRR have not been included. Thus, it is important to comprehensively understand the reconstruction or construction of facilities against tsunamis after the GEJE and attempts at biodiversity conservation and to assess this process from the viewpoint of green and hybrid infrastructure. Several works have addressed these reconstruction or construction works (Koshimura and Shuto 2015; Sakamoto 2016; Kurosawa 2016; Furuta and Seino 2016), and a few have introduced attempts at biodiversity conservation (Kurosawa 2016; Furuta and Seino 2016; Takeuchi et al. 2016). However, relevant information is fragmented and not comprehensive. In this study, the infrastructure reconstructions after the GEJE and related attempts at biodiversity conservation, including administrative background, are categorized and reviewed as comprehensively as possible. From the viewpoint of green and hybrid infrastructure, especially of ecosystem services expected in coastal facilities, the attempts are evaluated, and lessons from the post-GEJE reconstruction are discussed.

2. Great East Japan Earthquake and posterior infrastructure reconstruction

2.1. Impacts of tsunamis on coastal areas

The 2011 earthquake off the Pacific coast of Tohoku, Japan, produced tsunami waves higher than 5 m with the highest reaching up to 35 m, which could be observed throughout approximately 580 km of the coast in East Japan (Haraguchi and Iwamatsu 2013; Mori and Takahashi 2012; see Shimada 2016 for outline of the damage of the disaster). The tsunami and land subsidence severely damaged the seawalls and coastal protection forests that were constructed and afforested on beaches before the disaster (Yeh, Sato, and Tajima 2013; Himiyama, Watanabe, and Hara 2014; Sakamoto 2016), although some of them are considered to have reduced deaths and building damage during the tsunami (Nateghi et al. 2016). Moreover, the tsunami and land subsidence seriously disturbed the biodiversity in the coastal areas of the Tohoku district. The tsunami resulted in erosion and in some parts, removed biotic communities along with the soil (Tanaka et al. 2012) or buried them under sand and mud (Richmond et al. 2012). A flood of seawater or brackish water that extended several kilometers inland also occurred, which was caused by the tsunami and land subsidence (Mori and Takahashi 2012; BCJ 2013; Koshimura, Hayashi, and Gokon 2014; Une and Koarai 2014; Hara et al. 2016).

Although the tsunami and land subsidence mostly damaged the biodiversity in coastal areas of Tohoku district, they did not equally affect all types of communities (Kurosawa 2016). For example, the vegetation on sandy beaches disappeared or was reduced in many areas owing to erosion or sedimentation (Hayasaka et al. 2012; Kanaya et al. 2012; Yuzawa 2013; Shimada, Kawanishi, and Hayasaka 2014), whereas, some of them survived the disaster and exhibited remarkable recovery (Yuzawa 2013; Shimada, Kawanishi, and Hayasaka 2014), and new sand dune vegetations emerged in some coastal areas (Shimada, Kawanishi, and Hayasaka 2014). New salt marshes emerged widely in seawater-inundated areas in lowlands that were paddy fields or coastal protection forests before the GEJE (Kurosawa 2016; Watanabe and Kurosawa 2015; Saito et al 2016; Suzuki 2016). The most remarkable aspect of biodiversity after the GEJE is the appearance of threatened or near-threatened aquatic plants or hygrophyte species in many tsunami-inundated areas (Kurosawa 2016; Suzuki 2016; Yamanouchi et al. 2020). These newly appeared plants may (1) have germinated from seed banks after the disturbance brought about by the tsunami or land subsidence, (2) have been carried from another location by the tsunami, or (3) have been dispersed from another area and established in the new location after the tsunami (Kurosawa 2016). A genetic study of newly emergent populations of a threatened sedge, Carex rugulosa, suggested their seed bank origin (Ohbayashi et al. 2017). Post-disaster reconstruction works have been implemented in these unique, unusual ecosystems.

2.2. Post-disaster reconstruction

The Japanese government and local governments in damaged areas promptly initiated recovery and reconstruction after the GEJE in March 2011, aiming to draw guidelines, plan, and reconstruct protection facilities against future tsunamis (Kurosawa 2016; Furuta and Seino 2016). The basic principles for post-disaster reconstruction were set out in the report of a committee of the Central Disaster Management Council, Japan (CTICET 2011a), published on September 28, 2011, about 6 months after the disaster. The essential part had already been established as interim guidelines on June 26, 2011 (CTICET 2011b) (Table 1). Many acts and guidelines based on these principles were developed for planning reconstruction in the affected areas within 2 years after the GEJE (Furuta and Seino 2016; Kurosawa 2020). Post-disaster reconstruction in coastal areas was initiated by the Forest Agency, Japan (FAJ), as early as October 2011. Post-disaster reconstruction and construction works, including the reconstruction of seawalls and coastal protection forests and construction of new green spaces, have continued after the GEJE, with works planned until 2021 (Koshimura and Shuto 2015; Kurosawa 2020). No cost/benefit analysis for these reconstructions, including the maintenance cost of facilities, has been conducted.

Table 1. Chronology of activities related to reconstruction of coastal protection facilities and green infrastructure or Eco-DRR after GEJE.

Year	Month	Activities related to reconstruction	Activities related to green infrastructure or Eco-DRR
2011	3	The Great East Japan Earthquake
	6	CTICET Interim Guideline (CTICET 2011b)
	7	Notice for height of sea walls by MLITTJ and MAFFJ
	9	Report of CTICET (CTICET 2011a)
	10	Reconstruction of coastal forests were started.
2012	1	Reconstruction of sea walls were started.
	2	Guideline for reconstruction of coastal forests by FAJ
	8		Opinions to FAJ by Society of Vegetation Science, Japan
	9		National Biodiversity Strategy Japan 2012–2020
	10–11		Opinions to prefectural governments by Ecological Society, Japan etc.
2013	12		Basic Act for National Resilience, Japan
2014	4		Proposal of use of coastal ecosystem in reconstruction by SCJ
	6		Fundamental Plan for National Resilience, Japan
	9		Proposal of encouragement of the use of ecological infrastructure by SCJ
	12		Amendation of Japanese Coast Act
2015	8		5th National Land Use Plan, Japan
			National Spatial Plan, Japan
	9		4th Priority Plan fr Social Infrastructure Development, Japan

2.2.1. Reconstruction of seawalls

Seawalls and wave-dissipating blocks were reconstructed in almost all lowlands, extending about 300-km in length of the Pacific coast of Tohoku, by the Ministry of Land, Infrastructure, Transport, and Tourism, Japan (MLITTJ), or the civil works departments of prefectural and exceptionally by the FAJ in sea-facing national forests (Kurosawa 2016; Furuta and Seino 2016) (Figures 1, Figures 2, Figures 3(a,Figures 3b)). Most of them had already been constructed before the GEJE, and their reconstruction works included increasing the height of the wall and expanding its foot toward the coast (Kurosawa 2020). The height of seawalls was determined by calculating the wave heights of the GEJE and historical tsunamis and simulations according to a notice provided by the MLITTJ and Ministry of Agriculture, Forestry, and Fisheries, Japan (MAFFJ), on July 8 2011. They were assumed to protect against “frequently occurring tsunamis” (meaning more than once every 200 years) based on the essential part of the basic principles for post-disaster reconstruction, by CTICET (2011b) (Koshimura and Shuto 2015; Harbitz et al. 2016). Along the Sendai Bay, seawalls with a height of T. P. (mean sea level of Tokyo Bay) 6.2 m and extending approximately 50 km in length, that were destroyed in the GEJE, were reconstructed with a height of T. P. 7.2 m (Koshimura and Shuto 2015; Kurosawa 2016; Furuta and Seino 2016). The height of the reconstructed walls reached approximately T. P. 15 m in the deeply indented coastlines in Iwate and northern Miyagi Prefectures (Furuta and Seino 2016).

Figure 1. Locations of coastal protection facilities against tsunamis in Pacific side of southern Tohoku district, Japan, after GEJE. Small green spaces for disaster prevention in Miyagi Prefecture are omitted. Many seawalls are scattered on lowland in rias coast lines in Pacific side of northern Tohoku district. Satellite image on December 14 2015 by Google Earth was downloaded on August 28 2020.

Figure 2. Schematic drawings of seawall and coastal protection forest reconstructed after the GEJE. Drawings are modified from Mabuchi, Yamanouchi, and Kurosawa (2021).

Figure 3. Coastal protection facilities against tsunamis reconstructed or constructed after the GEJE. A: Facilities; from seaside, wave-dissipating blocks, seawall, and coastal protection forest (Isobeosu in Soma city, Fukushima Prefecture, Japan, on October 3 2018). B: Seawall (Isobeosu in Soma city, Fukushima Prefecture, Japan, on August 31 2018). C: Coastal protection forest (Isobeosu in Soma city, Fukushima Prefecture, Japan, on August 20 2018). D: Green space for disaster prevention (Hisanohama in Iwaki city, Fukushima Prefecture, Japan, on May 30 2018).

In Japan, seawalls are set along the nearest ground to the coastline among coastal protection facilities. The arrangement is also adopted in post-disaster reconstruction after the GEJE. It is not based on efficiency or safety, but as a result of the sectionalism of administration in Japan. MLITTJ is responsible for coasts, and FAJ is responsible for the coastal protection forests behind them. Hydraulic model experiments have shown that the arrangement of coastal protection forests on the seaside and seawalls on the inland side is more effective for decreasing the inundation depth of tsunamis (Iimura et al. 2017a, 2017b).

Seawalls and wave-dissipating blocks are typically gray infrastructures as they are artificial concrete facilities (Sebesvari et al. 2019). Although the notice by MLITTJ and MAFFJ on July 8, 2011, instructs each local department of coastal management in the prefectural government to consider biodiversity, environmental conservation, harmonization with the surrounding landscape, economic efficiency, maintainability, construction constraints, and accessibility to the public when deciding the height of seawalls, these were disregarded, and the plans of wall height were decided based on past tsunami height and simulations (Furuta and Seino 2016). Furuta and Seino (2016) pointed out the difficulties faced by the Regional Department Bureau of MLITTJ and the civil works departments of prefectural governments to propose practical plans for seawall construction according to the instruction, due to the severe situations just after the GEJE, namely, the disruption and shock in local communities and loss of many lives, including officials of the bureau and the departments. As a result, the reconstruction plans tended to apply numbers presented in the notice by the central government, and irrespective of land use, the seawalls in plans were huge and uniform in each region. Moreover, wall feet expanded with increasing height and, in most cases, toward the coast side, which resulted in the destruction of sandy beaches and respective vegetation (Oka and Hirabuki 2014). In some coasts, the plans for the reconstruction of seawalls were questioned by environmental organizations, societies, and even by residents (Furuta and Seino 2016). The Ecosystem Management Committee, Ecological Society of Japan, and two other societies submitted written opinions to prefectural governments in October–November 2012, stating that the reconstruction of seawalls should consider biodiversity conservation (Nemoto, Fujiwara, and Kurosawa 2013; Nishihiro, Hara, and Hirabuki 2014). Moreover, they were apprehensive about the seawalls obstructing the movement or migration of animals and dispersal of plants between sandy beaches and other coastal ecosystems (Oka and Hirabuki 2014).

2.2.2. Reconstruction of coastal protection forests

Coastal protection forests were reconstructed in almost all lowlands along the Sendai Bay by FAJ or the agriculture and forestry departments of prefectural governments (Kurosawa 2016; Furuta and Seino 2016) (Figures 1, Figures 2, Figures 3(a,Figures 3c)). To reduce the damage caused by coastal sand blows, strong winds, flood tides, and tsunamis to villages, cities, rice paddies, and other inland crops, coastal afforestation with Japanese black pine, Pinus thunbergii Parl., had been done on coastal dunes or reclaimed wetlands since the Edo era (1603–1868) (Kurosawa 2016; Sakamoto 2016; Furuta and Seino 2016). Recently, coastal protection forests have been defined by law and regarded by communities as multifunctional forests that could contribute to public health as a venue for recreation and to landscape by improving scenic beauty. The reconstruction works of coastal protection forests after the GEJE include expanding their areas and including mounding (Kurosawa 2020; Mabuchi, Yamanouchi, and Kurosawa 2020) (Figure 2). The mounding was approximately 3 m high and more than 200 m wide in coastal protection forests, following the guideline provided by a committee of FAJ in February 2012 (Figures 2, Figures 3(a)). The guideline indicates that more than 200 m wide coastal protection forests and 2–3 m high mounding for surviving coastal protection forests against tsunamis are needed to reduce the range of inundated areas, based on observations of damaged coastal protection forests by the GEJE and a simulation (Sato et al. 2012; Noguchi et al. 2012; Watanabe et al. 2014; Sakamoto 2016; Kurosawa 2020). However, the simulation was rather simple and preliminary.

Coastal forests are often regarded as green infrastructure (Renaud and Murti 2013; Kim et al. 2017; Natuhara 2018; Sebesvari et al. 2019), and the coastal protection forests reconstructed after the GEJE have occasionally been introduced as examples of green infrastructure or Eco-DRR (NCB MEJ (Nature Conservation Breau, Ministry of the Environment, Japan) 2016; Takeuchi et al. 2016). However, the reconstruction of coastal protection forests after the GEJE resulted in the destruction of unique ecosystems in tsunami-inundated areas as mentioned previously, burying newly appeared wetlands and threatened plants, insects, and fishes (Nishihiro, Hara, and Hirabuki 2014; Kurosawa 2016; Furuta and Seino 2016). Low vegetation and high bare soil cover with scarce coastal plants on the mound of coastal protection forests have been reported (Mabuchi, Yamanouchi, and Kurosawa 2020; Yamanouchi, Mabuchi, and Kurosawa 2021). Respectively, Nishihiro, Hara, and Hirabuki (2014) and Furuta and Seino (2016) directly and indirectly criticized protection forests after the GEJE as “inappropriate” from the point of view of green infrastructure. Furuta and Seino (2016) noted that no ecological scientists were involved in developing reconstruction policies at the national level. In contrast, a forest ecologist took part in the committee of FAJ that provided the guideline for the reconstruction of coastal protection forests in February 2012. The guideline indicates that considerations of the extent of damage in local communities, ecosystem conservation, and economic efficiency, including maintenance cost, are necessary. In addition, the guideline also states that the width of each coastal protection forest should be decided considering the current condition of land use, and mounding should be implemented if necessary. The Japanese National Academy of Science Council of Japan (SCJ) published a proposal on the use of coastal ecosystems (sand dunes, wetlands, and coastal forests) in the reconstruction of coastal protection forests on April 23, 2014 (SCJ 2014). These notes in the guideline and proposal were disregarded by the District Forest Offices of FAJ and the agriculture and forestry departments of prefectural governments, partly because of the severe situation of the local authorities just after the GEJE, as mentioned by Furuta and Seino (2016). As a result, coastal protection forests proposed in the plans expanded more than 200 m wide in almost all lowland coastal areas along the Sendai Bay, with no consideration of land use, and uniform flat mounds of about 3 m high were constructed for the forest (Nishihiro, Hara, and Hirabuki 2014; Kurosawa 2016; Furuta and Seino 2016) (Figure 1). The forest of Watari in Miyagi Prefecture, which was introduced as an example of Eco-DRR by Renaud and Murti (2013) and Takeuchi et al. (2016), was no exception. Moreover, mounds were made using the sand obtained from sandstones in the adjacent hills (Kurosawa 2016; Mabuchi, Yamanouchi, and Kurosawa 2020), not by coastal sand according to traditional and technically established procedures for coastal afforestation (Wakae 1961; Sasaki, Tanaka, and Sakamoto 2013). Within 3 years of construction, the mounds were characterized by low vegetation and high bare soil cover, with scarce coastal plant species, and they were dominated by annual or perennial herbs associated with early secondary succession, as a consequence of few buried seeds in the mounding materials (Mabuchi, Yamanouchi, and Kurosawa 2020; Yamanouchi, Mabuchi, and Kurosawa 2021). The plans for the reconstruction of coastal protection forests were also questioned by societies and some environmental organizations such as the Nature Conservation Society of Japan (Nemoto, Kurosawa, and Fujiwara 2013; Nishihiro, Hara, and Hirabuki 2014; Furuta and Seino 2016). The Society of Vegetation Science, Japan, submitted a written opinion to FAJ on August 14, 2012, stating that the reconstruction of coastal protection forests should be implemented to avoid mounding as much as possible. However, most of the environmental organizations and residents did not consider these plans problematic as they even volunteered in the planting of mounds. They were probably affected by the unconditionally favorable impression of afforestation in Japan.

2.2.3. Construction of green spaces for disaster prevention

Green spaces for disaster prevention were occasionally constructed in lowlands along the Sendai Bay by the civil works departments of local governments (Kurosawa 2016) (Figure 1). Green spaces show a wide range of diversity in their scale (dozens to a thousand meters), shape (patchy to a belt), location (just behind seawall to a few hundred meters apart from it), land use (playing park to plantation), and planted trees (coastal tree species to street or garden tree species). The properties and characteristics of these green spaces differ between the local governments that constructed them. In the Fukushima Prefecture, green spaces for disaster prevention were constructed on relatively extensive grounds where residential areas had existed before the GEJE and were situated just inland of seawalls instead of coastal protection forests (Kurosawa 2020). In Miyagi Prefecture, green spaces were constructed on relatively small grounds of diverse land use before the GEJE and were on the inland side of coastal protection forests, which were themselves situated on the inland side of seawalls. Figure 3(d) shows an example of the Fukushima Prefecture’s belt-type green space situated between a seawall and a road, where various coastal tree species were planted. Green spaces are constructed by local governments under their responsibility. Although there are no notices or guidelines by the central government, green spaces usually accompany mounding with relatively gentle slopes and, more or less, include plantations of various types of tree species.

The Fukushima Prefecture’s green spaces for disaster prevention can be regarded as a hybrid infrastructure, since they involved tree planting on artificial mounds in residential areas in the past. Although green spaces and coastal protection forests are quite similar in that they accompany mounds, and burying the original ground, it is a rare case that the former destroyed unique ecosystem situations in tsunami-inundated areas (Kurosawa 2020). The Miyagi Prefecture’s green spaces were sometimes constructed on newly appeared wetlands in the tsunami-inundated areas but their sizes were considerably smaller compared with those in coastal protection forests. Because of these reasons, societies, environmental organizations, and residents do not tend to question the plans for the construction of green spaces for disaster prevention.

3. Green infrastructure and Eco-DRR in the post-GEJE reconstruction

3.1. Gap between Japanese domestic policy related to green infrastructure and Eco-DRR and reconstructed facilities

Green and hybrid infrastructure or Eco-DRR was expected in domestic policies after the GEJE (Table 1). The Eco-DRR concept was introduced in Japan through an expert workshop organized by the International Union for Conservation of Nature (IUCN), United Nations Environment Programme (UNEP), and United Nations University (UNU), held in a GEJE-affected area, Sendai, Japan, in 2012 (Furuta and Seino 2016). The National Biodiversity Strategy of Japan 2012–2020 (Cabinet decision on September 28, 2012) stressed the importance of conserving and restoring ecosystems to reduce disaster risk. Subsequently, the Supplementary Resolution of Basic Act for National Resilience (enacted on December 11, 2013), the Fundamental Plan for National Resilience (Cabinet decision on June 3, 2014), and the Fifth National Land Use Plan (Cabinet decision on August 14, 2015) stated the intention of the government to promote Eco-DRR. In addition, the National Spatial Plan (Cabinet decision on August 14 2015) and the Fourth Priority Plan for Social Infrastructure Development (Cabinet decision on September 18, 2015) aimed to promote green infrastructure (NCB MEJ (Nature Conservation Breau, Ministry of the Environment, Japan) 2016) (Table 1). The SCJ published a proposal encouraging the use of “ecological infrastructure” for reconstruction and national resilience on September 19, 2014 (Nishihiro, Hara, and Hirabuki 2014; Kurosawa 2016; Furuta and Seino 2016). Thus, green and hybrid infrastructure and Eco-DRR have been promoted at the national level by the Japanese government after the GEJE, but the concept of green infrastructure or Eco-DRR was scarcely adopted in the planning of reconstructed coastal protection facilities in areas damaged by the GEJE, as previously mentioned. There is a gap between the situation of Japanese domestic policies related to green and hybrid infrastructure and Eco-DRR and the actual-reconstructed facilities in damaged areas. Furuta and Seino (2016) discussed this gap in detail based on practical experiences in reconstruction activities in several areas.

3.2. Changes in plans and the modification of facilities in the post-GEJE reconstructions for biodiversity conservation

Reconstruction of coastal protection facilities after the GEJE has been planned with little consideration regarding biodiversity despite the presence of many threatened species at construction sites (Kurosawa 2016, 2020). Some attempts have been made to include biodiversity conservation concerns in changes of plans or in modifications of facilities. These attempts include (1) unreconstruction or downsizing of seawalls, (2) setting back of seawalls, (3) designating conservation areas in coastal protection forests or a green space, (4) planting trees on seawalls, and (5) laying coastal sand on seawalls or mounds of coastal protection forests.

3.2.1. Unreconstruction or downsizing of seawalls

Almost all seawalls reconstructed in areas damaged by the GEJE have been built to faithfully comply with their reconstruction plans. Nonetheless, there are several exceptional coasts where seawall reconstruction was canceled or implemented in a smaller size than that in the early reconstruction plans, upon the request of local communities (Table 2). Moune in Kesennuma City, Miyagi Prefecture, is probably the only case where the seawall reconstruction was completely canceled (Figure 4(a)), resulting from the relocation of all residences to higher grounds and the fishermen’s enterprising activity for environmental conservation, which started before the GEJE (Furuta and Seino 2016). In several coasts with beaches in rias coastlines, seawalls were reconstructed in smaller sizes than those proposed in an early plan to prevent degradation of the landscape and damage to the local tourism industry (Furuta and Seino 2016; Takeuchi et al. 2016).

Table 2. Main coasts where seawall reconstruction were canceled or were implemented in smaller size by request of local communities after GEJE. Seawalls were reconstructed in smaller size at several other coast in Kesennuma-shi.

Coast or site name	Locality	Seawall	Purpose	References	Note
Kodano-hama	Kesennuma-shi, Miyagi Prefecture	downsizing from 11.6 m to 3.5 m	Tourism: Landscape for beach	Furuta and Seino 2016
Tanaka-hama	Kesennuma-shi, Miyagi Prefecture	downsizing from 11.6 m to 3.9 m	Tourism: Landscape for beach	Takeuchi et al. 2016; Furuta and Seino 2016
Moune	Kesennuma-shi, Miyagi Prefecture	unreconstruction (9.9 m in plan)	Tourism and fishery: Landscape and natural environment for oyster farming	Furuta and Seino 2016

Figure 4. Attempts made to include biodiversity conservation concerns in plans or in modifications of facilities after GEJE. A: Unreconstruction seawall at Moune in Kesennuma city, Iwate Prefecture (September 29 2017). B: Setting back of seawall at Okadashinhama in Sendai city, Miyagi Prefecture (August 17 2019). C: Conservation area in coastal protection forests at Isobeosu in Soma city, Fukushima Prefecture (August 18 2019). D: Green tide embankment at Ninokura in Iwanuma city, Miyagi Prefecture (July 12 2018). E: Laying coastal sand on seawall at Idohama in Sendai city, Miyagi Prefecture (August 19 2019). F: Laying coastal sand on mounds of coastal protection forest at Okada in Sendai city, Miyagi Prefecture (September 22 2018, photo by S. Mabuchi).

3.2.2. Setting back of seawalls

In most cases, new seawalls were reconstructed where old and damaged seawalls had been situated, as decided in plans. There are also three exceptional coasts where seawalls were reconstructed on the ground more inland to conserve coastal biodiversity (Table 3). The purposes and processes of seawall setbacks are different. In Otomoura in Rikuzentakata City, Iwate Prefecture, the seawall was set back 215-m inland to the restore tidal flat that reappeared on landfilled ground after the GEJE. The Rikuzentakata City government decided to set back the seawall for the expectation of its function in biodiversity conservation, recreation, and nature educational activity (Furuta and Seino 2016). The seawall in Gamo tidal flat in Sendai City, Miyagi Prefecture, was set back 80-m inland from that proposed in an early plan to reduce the damage to biodiversity (Kurosawa 2016; Furuta and Seino 2016) (Figure 5(a)). Some local residents and local environmental organizations objected to the early plan. Moreover, although the Miyagi prefectural government revised the plan and implemented the reconstruction of a setback seawall, some local residents and local environmental organizations opposed it (Furuta and Seino 2016). The MLITTJ set back a seawall 50-m inland on the Okada-shinhama coast in Sendai City (Nishihiro, Hara, and Hirabuki 2014; Ishikawa 2015; Kurosawa 2016) (Figures 4(b), Figures 5(b)). This process involved the participation of some experts in ecology and was implemented to conserve sand dune vegetation and coastal insect species.

Table 3. Main coasts where seawall were setted back for conservation biodiversity after GEJE.

Coast or site name	Locality	Distance of setted back of seawall	Purpose	References	Note
Otomo-ura	Rikuzentakata-shi, Iwate Prefecture	215 m	Biodiversity and recreation: Tidal flat	Kurosawa 2016; Furuta and Seino 2016
Gamo tidal flat	Sendai-shi, Miyagi Prefecture	20–30 m	Biodiversity: Tidal flat	Kurosawa 2016; Furuta and Seino 2016
Okadashinhama	Sendai-shi, Miyagi Prefecture	50 m	Biodiversity: Sand dune vegetation	Nishihiro, Hara, and Hirabuki 2014; Ishikawa 2015; Kurosawa 2016

Figure 5. Satellite images of reconstruction sites including biodiversity conservation after GEJE. A: Gamo tidal flat in Sendai city, Miyagi Prefecture, Japan (May 3 2019). B: Okada and Okadashinhama in Sendai city, Miyagi Prefecture, Japan (June 7 2018). C: Ido and Idohama in Sendai city, Miyagi Prefecture, Japan (September 19 2018). All images are downloaded from Google Earth on August 28 2020.

3.2.3. Designating conservation areas in coastal protection forests or green spaces

Several conservation areas without mounding were designated in reconstruction areas of coastal protection forests or construction areas of green spaces (Table 4), as many threatened or near-threatened aquatic plants or hygrophyte species were found in inundated areas where reconstruction or construction were planned. One of them was established in a green space construction area and other areas in coastal protection forest reconstruction areas. The protection area in Okada in Sendai City, Miyagi Prefecture, was situated on the inland side of the setback seawall in Okada-shinhama (Figure 5(b)). This protection area, where some ecology experts participated with, was implemented to conserve various coastal vegetation, marshes, ponds, and coastal forests that appeared after the GEJE and the old coastal protection forest that suffered and survived the GEJE. The Fukushima prefectural government and FAJ designated eight protection areas of approximately 18 ha in coastal protection forest areas in Soma City and Minamisoma City, Fukushima Prefecture, to conserve or restore coastal environments, primarily tidal flats, salt marshes, marshes, ponds, and grasslands (Watanabe and Kurosawa 2015; Kurosawa 2016; Mabuchi, Watanabe, and Kurosawa 2017) (Figure 4(c)). Investigations conducted on the flora and vegetation of most areas confirmed that threatened plant species and coastal vegetation were successfully conserved at least a few years after establishment (Watanabe and Kurosawa 2015; Mabuchi, Watanabe, and Kurosawa 2017). The conservation area in a green space in Shinchi town, Fukushima Prefecture, was established at the restored marsh. The ground in this area was temporarily filled and used for the deposition of disaster debris and construction materials (Kurosawa 2016).

Table 4. Conservation areas for biodiversity in reconstruction areas of coastal protection forest or green space after GEJE.

Site name	Locality	Reconstruction area	Area	Before GEJE	After GEJE	References	Note
Okada	Sendai-shi, Miyagi Prefecture	Coastal protection forest	ca 4 ha	Coastal protection forest	Marsh, pond, coastal forest and coastal protection forest without mounding and planting	Oka and Hirabuki 2017; Mabuchi, Watanabe, and Kurosawa 2017
Ido	Sendai-shi, Miyagi Prefecture	Coastal protection forest	ca 4 ha	Coastal protection forest	Marsh	Mabuchi, Watanabe, and Kurosawa 2017
Rachihama	Shinchi-machi, Fukushima Prefecture	Green space	ca. 2 ha	Paddy field	Marsh	Kurosawa 2016, 2020
Isobeosu (National forest)	Soma-shi, Fukushima Prefecture	Coastal protection forest	1.4 ha	Coastal protection forest	Tidal flat and salt marsh	Watanabe and Kurosawa 2015; Kurosawa 2016
Isobeosu	Soma-shi, Fukushima Prefecture	Coastal protection forest	ca. 11.3 ha	Coastal protection forest and ground of outdoor leaning center	Tidal flat, salt marsh, marsh and grassland	Watanabe and Kurosawa 2015; Kurosawa 2016
Iwanokohirukoya	Soma-shi, Fukushima Prefecture	Coastal protection forest	ca. 1 ha	Coastal protection forest	Tidal flat and salt marsh	Mabuchi, Watanabe, and Kurosawa 2017
Isobeseriyachi	Soma-shi, Fukushima Prefecture	Coastal protection forest	0.77 ha	Coastal protection forest	Pond and marsh	Mabuchi, Watanabe, and Kurosawa 2017
Isobeohama	Soma-shi, Fukushima Prefecture	Coastal protection forest	ca 0.6 ha	Coastal protection forest and residental area	Pond and marsh	Mabuchi, Watanabe, and Kurosawa 2017
Kabaniwamagome	Soma-shi, Fukushima Prefecture	Coastal protection forest	ca 0.32 ha	Paddy field	marsh	Mabuchi, Watanabe, and Kurosawa 2017
Kayahamasangenya	Minamisoma-shi, Fukushima Prefecture	Coastal protection forest	0.7 ha	Paddy field and Coastal Protection Forest	marsh	Mabuchi, Watanabe, and Kurosawa 2017
Shidokeminamiyachi	Minamisoma-shi, Fukushima Prefecture	Coastal protection forest	2.3 ha	Paddy field and Coastal Protection Forest	marsh	Mabuchi, Watanabe, and Kurosawa 2017

3.2.4. Planting trees on seawalls

After the GEJE, a tree-planting project, “A Green Tide Embankment,” was initiated, and this project held many tree-planting ceremonies in disaster-damaged areas, involving many residents, volunteers, and local governments. The goal of the project was to make forests on concrete seawalls by the mounding and planting of inland tree species, particularly evergreen broad-leaved trees. The Japanese Coast Act was amended to admit a modification of seawalls by mounding and planting trees as proposed by the project on December 10, 2014. However, making forests on concrete seawalls by mounding and planting has been questioned by ecologists and taxonomists, emphasizing that the large-scale plantation of inland tree species can harm coastal biodiversity, and the techniques used in making forests on concrete seawalls have not been established (Nishihiro, Hara, and Hirabuki 2014). The green tide embankment was not completely implemented, even though it had been planned for the Sendai Bay seawalls by the MLITTJ. Three experimental sites were established along the Sendai Bay, and the growth of planted trees has been surveyed and monitored (Figure 4(d)).

3.2.5. Laying coastal sand on seawalls or mounds of coastal protection forests

Coastal sand was laid on seawalls or mounds of coastal forests in a few coasts to establish sand dune vegetation from the seed bank (Table 5). On the mounds of coastal protection forests made of sand obtained from sandstone in adjacent hills, low vegetation and high bare soil cover spread, and coastal plant species are poor (Mabuchi, Yamanouchi, and Kurosawa 2020; Yamanouchi, Mabuchi, and Kurosawa 2021). Coastal sand was laid on some mounds of coastal protection forest in Okada in Sendai City, Miyagi Prefecture, by FAJ, through the participation of some ecology experts (Oka and Hirabuki 2017). A comparative vegetation survey on coastal protection forests showed an increase in coastal plant species in coastal sand-laid sites (Yamanouchi et al. unpublished data). Various attempts have been made to lay coastal sand on seawalls, which include laying coastal sands dredged at the adjacent estuary of the Nanakita-gawa River directly on the concrete wall at Okada in Sendai City, Miyagi Prefecture (Figures 4(e), Figures 5(b)); laying sands over the wall reconstructed using the cemented, sand, and gravel method at Idohama in Sendai City, Miyagi Prefecture (Figures 4(f), Figures 5(c)); and laying preserved sands at the reconstruction site on the upper part of the wall-mounted by sand obtained from sandstone in adjacent hills at Nakahama in Yamamoto town, Miyagi Prefecture, which is one of the experimental sites of the green tide embankment mentioned previously. Although sand dune vegetation seems to be established at each site, the effects of these attempts should be carefully studied and verified.

Table 5. Main coasts where coastal sands were laid on seawalls or mounds of coastal protection forests for establishing sand dune vegetation after GEJE.

Coast or site name	Locality	Protection facility	Scale	References	Note
Okadashinhama	Sendai-shi, Miyagi Prefecture	Seawall	ca. 140 m
Okada	Sendai-shi, Miyagi Prefecture	Mounds of coastal protection forest		Oka and Hirabuki 2017
Idohama	Sendai-shi, Miyagi Prefecture	Seawall	ca. 1200 m		Wall was constructed CSG method.
Nakahama	Yamamoto-machi, Miyagi Prefecture	Seawall	150 m		Sands were laid upper part of wall only

3.3. Lessons from the post-GEJE reconstruction

Seawalls and wave-dissipating blocks reconstructed after the GEJE are examples of gray infrastructure. Reconstructed coastal protection forests are “green” infrastructure in the sense of using plants against disasters; however, they also seriously damaged coastal ecosystems (Nishihiro, Hara, and Hirabuki 2014; Kurosawa 2016; Furuta and Seino 2016). Danielsen et al. (2005) suggested that mangroves and tree plantations attenuated tsunami-induced waves, protected shorelines against damage, and demonstrated their economic efficiency and benefits from ecosystem services of enhancing fisheries and forestry production by comparing artificial coastal protection structures. Regardless of whether they are natural or planted, coastal forests have received significant attention and have been studied as facilities against tsunamis (Wahyunto et al. 2009; Natuhara 2018; Wanger et al. 2020). Reconstruction of coastal protection forests by the mounding of sands from inland hills behind huge seawalls in the post-GEJE in Japan is a unique facility against tsunamis. NCB MEJ (2016) expected the formation of coastal landscapes, provision of habitats for wild species, and enhanced recreational attractions for ecosystem services of coastal protection forests reconstructed after the GEJE. Nishihiro, Hara, and Hirabuki (2014) focused on the provision of habitats for coastal species. Little studies exist on ecosystem services of coastal protection forests reconstructed after the GEJE, probably because they are not an attractive field of study at a first glance. Only a few studies on the biodiversity of the mounds of coastal protection forests have been conducted and have shown low vegetation and high bare soil cover with scarce coastal plants for several years after mounding and afforestation (Mabuchi, Yamanouchi, and Kurosawa 2020; Yamanouchi, Mabuchi, and Kurosawa 2021). Although there is no careful study on the role of coastal protection forests in other ecosystem services, i.e., the formation of coastal landscape and enhanced recreational attractions, it cannot be expected for at least several years due to their low vegetation (Figure 3; Yamanouchi et al. unpublished data). The mounds of green spaces, which have also been studied a little from the perspective of ecosystem services, seem to be the same as coastal protection forests, lacking coastal vegetation and species. Present states of coastal protection forests and green spaces would not sufficiently provide the expected ecosystem services.

Attempts for biodiversity and landscape conservation have been made and have established, designed, and managed in natural or seminatural areas. These attempts include unreconstructing or downsizing seawalls, setting back seawalls, designating conservation areas, and laying coastal sand on seawalls or mounds of coastal protection forests. All of these were designed to conserve specific-threatened or near-threatened coastal species, specific coastal vegetation, or certain small-scale ecosystems. Although most of their effects on conservation have not been verified, the target species, vegetation, and/or ecosystems were successfully conserved in several conservation areas (Watanabe and Kurosawa 2015; Mabuchi, Watanabe, and Kurosawa 2017). It should also be noted that the concept of green infrastructure was not applied to these attempts. However, some of them could be regarded as green infrastructure or hybrid infrastructure. Conservation areas are a kind of green infrastructure, set-backed seawalls with left sandy coast are hybrids of gray and green infrastructure, and seawalls covered by coastal sands are hybrid infrastructure, given that gray infrastructures are improved to restore coastal vegetation on them. Most attempts have been independently implemented and isolated without a strategically planned network. However, there are two exceptions. First is Okada and adjacent Okada-shinhama, where preserved sand dune vegetation by seawall setback, conservation areas for various coastal vegetation, and mounds and seawall laid with coastal sand are included. The area is called “Minami-Gamou Monitoring Site,” where various research projects and monitoring have been conducted (Kanno et al. 2014; Oka and Hirabuki 2014, 2015, 2017; Onza et al. 2014; Tomita et al. 2014, 2016; Takatsuki et al. 2018) (Figure 5(b)). Second is Ido and adjacent Ido-hama, where conservation areas for marsh and seawall laid with coastal sand are included (Figure 5(c)).

A huge tsunami disaster and subsequent-urged reconstructions resulted in the construction of huge artificial facilities against tsunamis in coastal areas without cost/benefit analyses. Coastal ecosystems have been damaged by post-disaster reconstruction works (Nishihiro, Hara, and Hirabuki 2014; Kurosawa 2016; Takatsuki et al. 2018). Nishihiro, Hara, and Hirabuki (2014) and Furuta and Seino (2016) noted lessons from this situation to prepare for future disasters. They highlighted the importance of pre-disaster preparation, environmental impact assessment before reconstruction, and the importance of the philosophy and technology of green infrastructure. However, no proposal has been made for the improvement of ecological services in coastal reconstruction areas after the GEJE. Seawalls, coastal protection forests, and green spaces against disasters now occupy a huge part of coastal areas in the southern Tohoku district. It is then important to improve ecological services in these areas. To deliver ecosystem services expected for the coastal environment, the network of the sites, where attempts for biodiversity and landscape conservation have been made, must be planned. The results show that laying coastal sands on mounds of coastal protection forests improves the diversity of coastal plant species (Yamanouchi et al. unpublished data). Judging from the result, laying coastal sands on facilities is probably useful for building a type of corridor that links isolated conservation areas. However, attempts to lay coastal sands on facilities have been conducted for small areas at only several places and have not been studied sufficiently. There is also too limited knowledge on the impacts on environmental or social elements from post-disaster reconstruction after the GEJE. Studies on the present state of biodiversity and other environments and sociological studies are needed to improve ecological services from the reconstructed coastal area.

Acknowledgments

The author appreciates the contribution of Dr. Yoshihiko Hirabuki of Tohoku Gakuin University for his valuable information on reconstruction sites and their biodiversity in Miyagi Prefecture, Japan. The author also thanks Dr. Takashi Yamanouchi and Ms. Shiori Mabuchi for discussions on the biodiversity of coastal protection forests.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by the the Japan Society for the Promotion of Science [JP18H04146, JP19H04383].