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Smart adaptation activities and measures against urban flood disasters
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Smart adaptation activities and measures against urban flood disasters Sampei Yamashita a,∗ , Ryoichi Watanabe b , Yukihiro Shimatani c a b c
Kyushu Sangyo University, 2-3-1 Matsukadai, Higashi-ku, Fukuoka 813-8503, Japan Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
a r t i c l e
i n f o
Article history: Received 31 August 2015 Received in revised form 7 April 2016 Accepted 29 June 2016 Available online xxx Keywords: Rainwater harvesting Flood disaster Mitigation
a b s t r a c t Frequent inundation has become a serious problem in urban areas. It is necessary to improve rainwater retention/infiltration in the urban watershed. The purpose of this study is to report how private rainwater-retention/harvesting facilities can be spread gradually but steadily in the city by citizeninitiated activities. Rainwater harvesting tanks were installed intensively and a rainwater harvesting house was constructed in the city of Fukuoka, Japan after the city experienced a flood disaster. The former enhanced users’ daily preparedness for emergency, and the latter inspired construction of a rainwaterharvesting housing complex. A public elementary school is in use from April 2016, which is inspired by these facilities. The school premises are located on the land reclaimed from an old irrigation pond. Thus the school needs to be adapted to this condition. 3000 m3 of rainwater can be retained within the premises. The amounts of retention and discharge are monitored, and the data is utilized for science education. In big cities, people tend to depend too much on the top-down, mega-system, which invites more impervious surfaces in urban areas. Bottom-up, individual/collaborative approaches should be adopted in order to achieve multiple purposes of preventing/mitigating disasters, preserving/conserving ecosystems and nurturing/rebuilding communities in the city. © 2016 Elsevier Ltd. All rights reserved.
1. Introduction A river is indispensable for sustaining a quality environment for diverse forms of life whereas it becomes a source of trouble with the overabundance of water. Frequent inundation has become a serious problem in urban areas all over the world (WMO/GWP, 2008). This is because the impervious surface covers most of the city area, and rainfall in the city tends to intensify due to heat-island effect and global warming. Measures such as dredging rivers, strengthening drainage systems and constructing flood walls are needed (Muller, Biswas, Martin-Hurtado, & Tortajada, 2015); however, they drastically change the urban riverine ecosystem (Palmer, Liu, Matthews, & Mumba D’Odorico, 2015). Moreover, these public works are insufficient as the urban-flood disaster inevitably deteriorates without decreasing runoff per se. It is necessary to devise and implement effective measures for rainwater retention and infiltration within
∗ Corresponding author. E-mail addresses: [email protected] (S. Yamashita), [email protected] (R. Watanabe), [email protected] (Y. Shimatani).
the entire urban watershed where there are usually a huge number of private properties and enterprises situated. Furthermore, restoring the hydrologic cycle by utilizing the green infrastructure can be cost-effective and lead to a relevant policy change even in a metropolis like New York (NYC, 2014). In order to promote green infrastructure effectively, it is crucial to use a wide range of combinations of innovative rainwaterharvesting measures, rather than focusing on single innovations (Marsalek and Schreier, 2009). Moreover, accurate design and configuration, simulation, localization and imposing proper maintenance schemes are indispensable in executing the rainwater harvesting system (GhaffarianHoseini, Tookey, GhaffarianHoseini, Yusoff, & Hassan, 2015). This study reports private, small- to mid-sized rainwater harvesting tools/facilities installed in urban watersheds and their impacts on the public, flood-disaster mitigation. It also shows a large-sized facility constructed in another watershed. The facility has not only a rainwater-retention function but also ecological and educational roles. This study compares the facilities’ functions with each other and examines their effectiveness as rainwater harvesting systems.
http://dx.doi.org/10.1016/j.scs.2016.06.027 2210-6707/© 2016 Elsevier Ltd. All rights reserved.
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Fig. 1. Study sites.
The purpose of this study is to report how private rainwaterretention/harvesting activities can be spread gradually but steadily in the city, as a citizen-initiated, smart way to responding to urban flood-disaster risks in Japan. 2. Scope In this study, we deal with rainwater retention/harvesting tools/facilities in the city of Fukuoka (population: 1.53 mil.; area: 340 km2 ), Japan and its suburbs: Itoshima (97,000; 216,km2 ) and Shingu (29 000; 19 km2 ). First, we are focused on the Hii River Basin located within Fukuoka (Fig. 1). The lower areas in the watershed have experienced inundations three times since 1960. The latest took place in 2009, and just after this event, a citizens’ alliance for flooddisaster management was established (Yamashita et al., 2013). This group consists of a wide variety of stakeholders including victims of the disaster, residents in general, academics and college students studying watershed management, NPO members involved in water resources management, construction engineers, local government officials, etc. They have been trying to come up with ideas to tackle urban water challenges and practice what they can do together for a comprehensive flood control. Second, we move onto Itoshima and Shingu, both of which need to respond to a growing population as suburbs of Fukuoka (Fig. 1). In association with the activities for the Hii River Basin, an apartment complex featuring rainwater-harvesting facility was built in 2012 in Itoshima, and a public elementary school with rainwater retention/harvesting functions is in use from April 2016 in Shingu. In this study, we explain what the philosophy of these facilities is and how they are relevant to one another. 3. Citizens’ alliance for the Hii River Basin management 3.1. Hii River Basin and flood disaster in 2009 The watershed area of the Hii River is included within the Fukuoka city area (population: 1.53 mil.), which is located in the north of Kyushu, one of the main islands of Japan (Fig. 1). The area of the watershed is relatively small; it is only 29 km2 , and the length of the main channel is 13 km. The urbanized areas account for about 70% of the watershed area, and about 180,000 people live there. Three areas close to the Hii River were inundated due to heavy rainfall on July 24th, 2009. The rainfall was so intense; its amount reached about 100 mm/h. As the drainage system of the area is
designed to manage the rainfall intensity of up to 52 mm/h, it was naturally overwhelmed. The rapid and concentrated runoff due to urbanization made the inundation even worse; 410 houses were flooded within this small watershed (Fig. 2).
3.2. Citizens’ alliance In response, we decided to provide a new forum for citizens including local residents, local officials, businesses, engineers, students, academics, etc. to share views regarding floods and flood prevention/mitigation. As there are many kinds of stakeholders involved in this endeavor, all they need is to put aside their differences and work together to solve the problem. The group call themselves “Citizens’ Alliance for the Hii River Basin Management.” In order to share views and come up with voluntary runoffcontrol measures, the group carries out forums and fieldworks by themselves. The forums have been held 43 times from October 4, 2009 up until May 25, 2015. Around 100 people have participated in each forum. The 43 forums can be classified into six phases: 1) Introduction, 2) Development, 3) Technical recommendations, 4) Actions, 5) Involvement in drawing up the river development project, and 5) Safety plan for 100 mm/h-rainfall.
3.2.1. From introduction to technical recommendations During the period from the Introduction to Technical recommendations phases, the Alliance tried to build consensus and come up with ideas for comprehensive flood control. In the Introduction phase (Oct. 2009–Jan. 2010), the Alliance discussed and compiled recommendations and proposals for the comprehensive flood control and watershed management of the Hii River and submitted them to the mayor and governor of Fukuoka. In the Development phase (Feb.–Dec. 2010), NPO and student members of the Alliance took advantage of the prefectural monitoring system for rainwater harvesting and started to install rainwater retention/harvesting tanks (0.2 m3 ) to households willing to use one for free. The activity led most participants, including those who had experienced inundation and demanded immediate preventive measures, to agree to incorporate multiple rainwater retentions into flood control as an essential measure. In Technical recommendations phase (Jan.–May 2011), experts proposed redesigns of a closed schoolyard and an irrigation pond for effective rainwater retention/infiltration in the watershed and explored the possibility of constructing a rainwater harvesting house as a model housing
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Fig. 2. Three areas (Torikai, Tajima and Nagao) are inundated in the Hii River Basin (left). Over 20 mm/10 min rainfall was observed at 7pm on July 24, 2009 (upper right), and the river water overflowed (lower right).
project in the watershed (these three phases and part of the Actions phase are described in detail in Yamashita et al., 2013). 3.2.2. Actions (Jun. 2011–Mar. 2013) In the Actions phase, the Alliance tried to implement what they could do to prevent/mitigate flood disasters as individual and communal efforts. They carried out an awareness building workshop for children and promoted individual runoff reduction among the next generation in the future, participated in a traditional rejuvenation event of one of the irrigation ponds and decided that they would create “Hii-Kawa Gakko (Hii River School)” to promote runoff reduction among younger generations (Yamashita et al., 2013). Moreover, the Alliance initiated the design and implementation of risk management measures. For instance, recorded flood depth signs were installed in the inundation area of July 2009 Fukuoka flood (Fig. 3). The residents and college students took part in sign-design workshops in 2013. The workshops took into consideration both legibility and aesthetics as the sign were not only to be looked at just before flooding but also to be seen daily by both residents and visitors in the city. In addition, participants selected the color in the sign indicating the recorded flood depth to correspond to that in the inundation hazard map that had already been distributed by the city government in 2010. Thus they took care of the sentiment of those who had feared a decline in the land prices. In association with a ward office of the city government of Fukuoka, the Alliance devised a guidebook for evacuation when/before heavy rainfall and distributed it in March 2013 for the residents of Tajima, one of the inundated areas (Figs. 2 and 4). Workshops were carried out both for devising the guidebook and for explaining it to those who were concerned about flood-disaster risk management. This activity led to similar ones in other inundated areas, Torikai and Nagao (Fig. 2), in the Hii River Basin. Educational materials were deigned to nurture public awareness for flood-disaster risk management from early on. A local folklore/myth, which involved a giant, eight-necked serpent representing the river and flood disasters and a god/goddess symbolizing flood-disaster risk management, was incorporated in the design of a file folder to be used by children (Fig. 5).
Fig. 3. Recorded flood depth sign installed in March 2013 in the inundation area of July 2009 Fukuoka flood (upper), and a sign-design workshop by residents and college students in December 2012 (lower).
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Fig. 4. Guidebook (front cover (left) and p.7) for evacuation in Tajima, one of the inundated areas of July 2009 Fukuoka flood in the Hii River Basin.
Fig. 5. A file folder (left) and playing cards both designed for children to learn flood-disaster risk management. The cards are used at flood disaster risk management drills involving children (right).
Playing cards were also designed for children to learn importance of rainwater harvesting with pleasure. The messages in the cards were discussed in the forums and workshops by the Alliance, and the images in the cards were designed by college students studying child education based on the messages. The cards have been used in flood disaster risk management drills where children participate (Fig. 5). The rainwater harvesting house that had been discussed in the Technical recommendations phase was constructed in the watershed in May 2012 in the Actions phase. 3.2.3. Involvement in drawing up the river development project (May 2013–May 2014) The prefectural government of Fukuoka published the “Hii River System Development Project” in May 2014 (Fukuoka Prefectural Government, 2014). The project is stipulated by River Act of Japan and referred to for 30 years from publication. In the process of drawing up the plan, the local government needed to incorporate public comments into it. As they have been collaborative with the Alliance from the beginning, they attended the forums and explained the draft to the participants in January 2014. In response, the alliance provided over 100 comments on the draft, which were taken into consideration by the government revising the draft.
As a result, two significant revisions were made in the plan: 1) A registration system called “safety plan for 100 mm/h-rainfall,” a scheme for preventing and mitigating inundation caused by extremely heavy, short-term rainfall (such as 100 mm/h-rainfall) is written clearly in the clauses of the plan as a set of measures for runoff reduction, and 2) when the safety plan is established before long, the river development project can be revised in less than a decade, which is the period originally set for a possible readjustment of the project. The description of the safety plan for runoff reduction in the legal river development project is quite unique and rare as it requires administrators of the river and storm-water drainage system to cross-sectionally collaborate. 3.2.4. Safety plan for 100 mm/h-rainfall (Jul. 2014–May 2015) The system of “safety plan for 100 mm/h-rainfall” was established in April 2013 by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT, 2014). This has much to do with one of the policies the Japanese government has implemented to tackle flood disasters especially in urban areas in a comprehensive way since the late 1970s (MLIT, 2010). The plan is intended to mitigate food damage in urban areas not only by improving river channels and drainage systems but also
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by installing rainwater retention/infiltration facilities/functions all over the urban river basin. It expects river and drainage-system administrators, residents and private firms to collaborate and mitigate flood disasters by reducing surface runoff and sharing safety/risk information. MLIT requires potential municipalities to incorporate the following three aspects into their plan: • The targeted rainfall intensity must be greater, more local and shorter-lasting than the intensities set in both the legal river development project and storm-water drainage project. • River and drainage-system administrators, residents and private firms must work collaboratively and mitigate flood disasters by reducing surface runoff and sharing safety/risk information. • Measures focused on flood-damage reduction must be emphasized. The municipalities registered include the city of Nagoya, a metropolis (population: 2.28 million), and nine mid- to small-sized cities registered as of the end of December 2014. In Fukuoka, the Citizens’ Alliance for the Hii River Basin Management is collaborating with both the city and prefectural governments for drawing up the safety plan. The members of the Alliance find it indispensable to objectively demonstrate how effective it is to reduce runoff by individual and communal activities, and how those efforts are spread in wider urban areas, in order to materialize the safety plan in Fukuoka and to revise the Hii River System Development Project in the near future. In the following sections, we would like to address a wide variety of rainwater retaining/harvesting/infiltrating facilities installed not only in the Hii River Basin but also in nearby urban areas and show how they are relevant to each other.
Fig. 6. Rainwater retention/harvesting tank (0.2 m3 ).
Table 1 Categories and items of the questionnaire. Category
Item
Attribute
Address Family Initiative
Use
Knowledge on the campaign Purpose Usage Rainfall-information gathering Discharge before heavy rainfall Change in water charge Favorable feature
Awareness
Preparedness for rainfall Promotion/recommendation
Function
Design Needed capacity Price Operation Prior means for retention Water quality Publicity
Greening
Amount Intent of increasing green and the reason
4. Private tanks 4.1. Rainwater-harvesting tank Small- to mid-sized rainwater retention tools/facilities have been installed in the Hii River Basin since 2009. Naturally, just after the disaster in 2009, the victims did not pay much attention to rainwater retention but demanded immediate and direct measures involving larger rainwater pumping/discharge systems and higher floodwalls. They accused the local governments of having not taken effective measures. At first, it thus seemed quite difficult to build consensus for runoff reduction among the citizens involved (Yamashita et al., 2013). However, the tide turned after the NPO and college students intensively installed rainwater harvesting tanks (Fig. 6) for free (the tanks were provided by local governments) for the residents including the victims in 2010 (Section 3.2.1). Afterwards (Oct.–Dec. 2010), we carried out a questionnaire survey for the residents (96 households) who had the rainwaterharvesting tanks installed (106 tanks) and inquired about their attitudes toward the rainwater management (Table 1). The response rate was 86.5% (83/96). As a result, in terms of runoff reduction, it is found that flood-disaster mitigation/prevention is not considered to be the major reason for the users to retrofit the barrel; using rainwater for gardening etc. (54%) tops the list of the purposes, followed by water-saving in general (35%) and flood-disaster mitigation/prevention (9%). However, most of the users of the tank (82%) became more aware of the frequency and intensity of rainfall after they started to use retained water for gardening etc. (Fig. 7). 95% of them told their neighbors about advantages of the tank and recommended installation. 68% of the users replied that they would have gotten one even if it had not been free. The users attitudes
Fig. 7. Tank users’ awareness for heavy rainfall.
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Fig. 8. Rainwater-harvesting house. The blue of the plan (right) represents the cisterns (42 m3 in total).
Fig. 9. Rainwater harvesting from Jun. 2012–Dec. 2013. (a): water balance; (b): consumption/infiltration.
Fig. 10. Rainfall/discharge Aug. 30, 2013. At 14:00, rainwater was discharged into the storm-water drain.
implicate their enhanced daily preparedness for emergency, which is essential for an effective disaster evacuation. 4.2. Rainwater-harvesting house As the capacity of rainwater-harvesting tanks distributed in the watershed of the Hii River is 0.2 m3 , and the number of the tanks installed was only 106 at that time, their substantial function for runoff reduction is quite limited. The Alliance thought they needed to develop rainwater retention/harvesting as a housing system and demonstrate it to the public. As mentioned in section 3.2.2, a rainwater-harvesting house was constructed in 2012 in the Hii River Basin (Fig. 8). The owner of
the house is a member of the Alliance. The cisterns of the house retain about 42 m3 of rainwater and cost about \4,000,000. The unit cost is as low as a sixth of a big rainwater-storage (60,000 m3 )/discharge system established in 2012 by the city government of Fukuoka in another watershed (Fukuoka City Government, 2012). The rainwater retained is used domestically, and the amounts of input-output are closely monitored. Fig. 9 shows how the rainwater had been either used by the family or infiltrated into the soil during the period from Jun. 2012 to Dec. 2013. Around 50% of the rainfall in total was used domestically for flushing toilet, washing, bath etc., and the remainder seeped into the ground.
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nal garden, toilet and air conditioning. The input/output to/from its cistern is also closely monitored. Real-time data have been open to the public since Oct.19, 2014, and they can be accessed online without restriction (Moriyama). The structure of the cistern is unique; it is filled with crashed stones to sustain the structure, and the walls and the bottom are made of plastic. Thus the cistern is not so expensive. The unit cost is about \31,000/m3 , which is a third of that of the rainwaterharvesting house in the Hii River Basin. 6. Smart school
Fig. 11. Mid-sized retention/harvesting housing complex.
In August 30, 2013, the facility experienced a heavy rainfall, and its peak rainfall intensity was 33 mm/10 min around 2 p.m. (Fig. 10). The rainfall inundated the downtown area of Fukuoka, and the inundation occurred down the hill where this house is located (15-min walk). However, the cistern of the house dealt with the rainwater effectively, and it spilled just 1 m3 of water in total from the storm-water infiltration inlet to the drainage during the peak rainfall around 14:00 (Fig. 10). It should also be noted that this is the only discharge (1 m3 (discharge)/400 m3 (rainfall)) to the public drainage during the period of 1.5 years from the start of the observation in Jun. 2012–Dec. 2013 (Fig. 9). 5. Communal cistern and garden In order to promote runoff reduction in the Hii River Basin, we need to develop a wide variety of private housing systems featuring rainwater retention/harvesting. The rainwater-harvesting house inspired the construction of a housing complex that has a function of rainwater harvesting in the adjacent city of Itoshima (Fig. 11). The complex was so popular that its apartments were sold out soon after sale in May 2012. The complex can retain over 100 m3 of rainwater (Fig. 12). The water is provided for its commu-
As for large-sized runoff reduction systems, we have helped to develop an effective combination of turf and pervious soil for a football field since before 2009 (Yamashita et al., 2013). A public elementary school is open from April 2014 by another, nearby municipality, the town of Shingu, inspired by the installation of the above-mentioned, small- to mid-sized rainwater-harvesting facilities. The knowledge from the football field construction is integrated into the new school facilities as well. The school premises are located on the land reclaimed from an old irrigation pond that had been left behind in the urbanizationdesignated area. Naturally, the land and surrounding areas allocated for residency are prone to inundation. It is thus necessary for the school to be adapted to this condition. 1600 m3 of runoff from the surrounding residential areas can be retained within the schoolyard, under which two rainwaterretention cisterns are installed. One of the cisterns (1000 m3 ) is also to retain rainwater from the surrounding areas whereas the other (200 m3 ) is to collect rainwater that is fallen on the schoolyard and used afterwards to water the lawn covering the ground (Figs. 13–15 ). The 1,000 m3 -detention cistern costs about \60,000/m3 , twothirds of the unit cost of the rainwater-harvesting house in the Hii River Basin. The same type of pervious soil used for the football field is utilized as foundation for the schoolyard. The school buildings also has another 200 m3 -cistern to retain rainwater fallen on the facilities. In the earlier planning stages, an architect recommended that the cistern be smaller (40 m3 ) and installed above ground level for generalized, maintenance reasons. However, as the school board learned that both the rainwater har-
Fig. 12. Cistern of the complex (>100 m3 ). By courtesy of Daiken.
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Fig. 13. Rainwater-retention system of an elementary school (3800 m3 in total).
The school had two more challenges to overcome: it faces railroads and factories. Without proper design and configuration of the facilities, noise and smoke would be a problem. Thus, it has been decided that 1) the gymnasium and its sound absorbing green walls are located close to the railroad to buffer classroom buildings from train noise; 2) parking lots distance them sufficiently from the factories; and 3) the courtyard is arranged to function as a seasonal-wind corridor for air exchange (Fig. 16). In designing and planning the school, the challenges reminded us of Katsura Detached Palace in Kyoto. This imperial villa was constructed in the alluvial plane along the Katsura River. The location gave it the advantage of bringing water from the river for attractive garden ponds but also created the risk of flooding (Morimoto, 2011). By smartly adapting to the risk–giving the main building a high floor and surrounding the palace with bamboo fences to reduce damage from flooding, this beautiful palace has been in harmony with nature for around 400 years (Morimoto, 2011). It is hoped that pupils would learn how their school is smartly adapted to the risks, and that they would take pride in attending this school. The project is thus called “Smart School Project”.
7. Comparison
Fig. 14. Perspective of the school under construction from November 7, 2014.
vesting house in Fukuoka and the housing complex in Itoshima had caused no major maintenance problems for over one and a half years, they decided to increase the capacity of the cistern and install it underground. The rainwater retained is used to flush the toilet etc. when water lifeline is disrupted by disasters and to water flowers to be grown by pupils. The rainwater-reuse system in the building is powered by photovoltaics. The water is also used for a school biotope to be built. The amounts of retention and discharge will be monitored, and the data will be utilized for science education.
Architectural Institute of Japan (2016) published “Technical Standards for Rainwater Harvesting (AIJES-W000-2016)” in March 5, 2016, the first such standards devised for promoting comprehensive rainwater harvesting systems in Japan. This is to encourage both private and public sectors to participate in rainwater harvesting systematically. The standards take local hydrology/geology into consideration, which is critical for rainwater harvesting systems to be successful (Hering et al., 2015). The standards aim to retain up to a height of 100 mm of rainwater on average within a site area; the height is set based on the local precipitation data. The aspects of rainwater harvesting include 1) flood control, 2) daily water use, 3) emergency water use, 4) and environmental conservation; flood control and daily water use are to be directly linked to the targeted rainwater-storage height. Emergency water use is for people to endure without public water supply for up to three days (0.05 m3 × 3 days × #people), which is based on the experience in Tohoku on March 11, 2011. Rainwater retention for environmental conservation involves infiltration and evaporation features of the site. Table 2 shows the rainwater-harvesting functions of the singlefamily house in Fukuoka (Section 4.2), the housing complex in Itoshima (Section 5) and the elementary school in Shingu (Section 6) utilizing the standards. The total heights of rainwater storage of the house and the school are 195.5 and 137.1 mm, respectively and exceed the targeted 100 mm-threshold. The flood-control function of the two facilities also surpasses the threshold (130.8 and
Fig. 15. Construction site Mar. 17, 2015. (a): groundwork; (b): preloading for schoolyard; (c): inlet for 1000 m3 -cistern.
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Housing complex
Elementary school
Total site area Rooftop Vegetation Permeable pavement Impervious pavement Pond etc. Schoolyard (soil) Schoolyard (turf) Others Infiltration rate Flood control storage tank capacity for the premises Flood control storage tank capacity for neighborhood Stormwater reservoir Cistern capacity (water use) Occupant Visitor Refuge User (total) Domestic use (flashing toilet/washing, etc.) Watering plants (turf/lawn, etc.) Water use (total)
100 100 297.91 105.72 192.21 – – – – – – 0.033 22.5 – – 19.3 4 – – 4 0.24 – 0.24
100 100 2700 955 345 600 – 15.4 – – 784.6 0.065 – – – 116.49 50 – – 50 1.5 3.5 5
100 100 20,113.17 5,765.30 1,000.00 – 6,371.87 – 3,603.50 3,372.50 – – – 1000 1600 400 900 – 100 1000 – 43.7 43.7
B. Flood control (mm)
Rooftop Vegetation Permeable pavement Impervious pavement Boardwalk/wood deck, etc. Schoolyard (soil) Schoolyard (turf) Stormwater reservoir Storage height for flood control by tank Storage height for flood control (total)
3.55 51.6 – – – – – – 75.5 130.76
4.4 10.2 10 – 1.9 – – – – 26.7
2.9 4 – 3.2 – 14.3 13.4 79.5 – 117.2
C. Daily rainwater use (mm)
Storage height for water use
64.8
43.2
19.9
D. Emergency water use
Water supply for emergency (m3 ) Storage height for emergency (mm)
– –
2.8 2.78
150 7.46
E. Environmental conservation (mm)
Storage height for environment
55.3
26.7
37.8
F. Total rainwater storage height (mm)
F=B+C
195.5
69.9
137.1
G. Deficit (mm)
G = A–F
−95.5
30.1
−37.1
H. Rainwater Storage ratio (%)
H = F÷A × 100
195.5
69.9
137.1
Calculation condition
a. Basic storage height (mm) A. Storage height aimed within the premises (mm) Surface condition (m2 )
Infiltration (m3 /h) Storage facility (m3 )
User (#person)
Rainwater used (m3 /day)
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Table 2 Rainwater-harvesting functions of the single-family house in Fukuoka, the housing complex in Itoshima and the Elementary school in Shingu based on “Technical Standards for Rainwater Harvesting (AIJES-W000-2016)”.
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Fig. 16. Configuration for the school facilities to adapt to the challenges of flooding, noise and smoke.
117.2 mm, respectively). The capacities for daily rainwater use of the two housing facilities are way greater than that of the school, whereas the school can serve more than 1000 people without public water supply for up to three days by the 200 m3 -cistern installed under the gym. The environmental conservation function of the facilities are also considerable (house: 55.3 mm; complex: 26.7 mm; school: 37.8 mm). The construction costs of the tanks installed in the house, the housing complex and the school are around 1/6, 1/12 and 1/9 of that of the above-mentioned municipal flood-control reservoir, respectively. Thus, it may be fair to say that these three facilities are cost-effective compared to the municipal gray infrastructure. 8. Concluding remarks As we saw in the previous sections, individual/collaborative approaches are cost-effective, ecofriendly and thus sustainable. In Fukuoka and its suburbs, installing small-/mid-sized rainwaterharvesting tools/facilities and the monitoring data have encouraged the public to get involved more in urban-runoff reduction. It is clear that taking small steps surely leads to safeguarding the city from flood disasters. Smart adaptation to flooding should be a prerequisite for the restoration of a sound hydrologic cycle in the city, and urban biodiversity in the long run. In big cities, people tend to depend too much on the top-down, mega-system involving dredging rivers, strengthening drainage systems, constructing flood walls, etc., which invites more manmade, impervious surfaces in urban areas. Even the city with its safety plan for 100 mm/h-rainfall leans toward mega-systems for runoff reduction. For instance, the city of Nagoya, Japan, which has implemented its registered safety plan since 2013, puts emphasis not on private efforts for runoff reduction but on large-sized rainwater retention/infiltration. In the watersheds targeted in Nagoya’s safety plans, there are large-sized public rainwater retention facilities installed that can retain 233,500 m3 of rainwater in total but no subsidy program for small-/mid-sized, private rainwater retention/harvesting tanks (MLIT, 2014). On the other hand, flood-disaster risks increase with excessive dependence on public works, as we have learned from the tsunami disasters in Tohoku (Hirano, 2013; Nakai, 2013).
Bottom-up, individual and/or collaborative approaches should be adopted in order to achieve multiple purposes of preventing/mitigating disasters, preserving/conserving ecosystems and nurturing/rebuilding communities in the city. We need to become more sensitive to hydrologic cycle by utilizing appropriate technology, and thus smartly adapt to flood- disaster risks in the city. References Architectural Institute of Japan. (2016). Technical standards for rainwater harvesting (AIJES-W000.-2016. In japanese with English summary). Tokyo: AIJ. Fukuoka City Government. (2012). Rainbow Plan Hakata. Fukuoka: Fukuoka City Government. http://www.city.fukuoka.lg.jp/doro-gesuido/keikaku/hp/ usuiseibirainbowplanhakata 1.html Fukuoka Prefectural Government. (2014). The Hii river system development project (in Japanese). Fukuoka: Fukuoka Prefectural Government. GhaffarianHoseini, A., Tookey, J., GhaffarianHoseini, A., Yusoff, S. M., & Hassan, N. B. (2015). State of the art rainwater harvesting systems towards promoting green built environments: a review. Desalination and Water Treatment, 1–10. Hering, J. G., Sedlak, D. L., Tortajada, C., Biswas, A. K., Niwagaba, C., & Breu, T. (2015). Local perspective on water. Science, 349(6247), 479–480. Hirano, K. (2013). Difficulties in post-tsunami reconstruction plan following Japan’s 3.11 mega disaster: dilemma between protection and sustainability. Journal of JSCE, 1(1), 1–11. Marsalek, J., & Schreier, H. (2009). Innovation in stormwater management in Canada: the way forward, overview of the theme issue. Water Quality Research Journal of Canada, 44(1), v–x. MLIT (Ministry of Land, Infrastructure, Transport and Tourism). (2010). Comprehensive flood control: effectiveness of the act of flood-disaster measures for designated urban rivers (in Japanese). Tokyo: MLIT. MLIT. (2014). Safety plan for 100. http://www.mlit.go.jp/river/kasen/main/100mm/ Morimoto, Y. (2011). Biodiversity and ecosystem services in urban areas for smart adaptation to climate change: do you Kyoto? Landscape Ecological Engineering, 7, 9–16. Moriyama, T. http://srtmonitor-env.elasticbeanstalk.com/ monitor?token=531c5aabe85c6 Muller, M., Biswas, A., Martin-Hurtado, R., & Tortajada, C. (2015). Built infrastructure is essential. Science, 349(6248), 585–586. Nakai, Y. (2013). Reconstruction plan of Otsuchi town, Kamihei county, Iwate prefecture. Journal of JSCE, 1(1), 242–250. NYC Environmental Protection. (2013). NYC green infrastructure: 2013 annual report. New York: NYC Environmental Protection. Palmer, M. A., Liu, J., Matthews, J. H., & Mumba D’Odorico, P. (2015). Manage water in a green way. Science, 349(6248), 584–585. World Meteorological Organization and Global Water Partnership (2008). Urban Flood Risk Management—A Tool for Integrated Flood Management, Associated Programme on Flood Management. Yamashita, S., Shimatani, Y., Watanabe, R., Moriyama, T., Minagawa, T., Kakudo, K., et al. (2013). Comprehensive flood control involving citizens in a Japanese watershed. Water Science & Technology, 68, 791–798.
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Smart adaptation activities and measures against urban flood disasters Sampei Yamashita a,∗ , Ryoichi Watanabe b , Yukihiro Shimatani c a b c
Kyushu Sangyo University, 2-3-1 Matsukadai, Higashi-ku, Fukuoka 813-8503, Japan Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
a r t i c l e
i n f o
Article history: Received 31 August 2015 Received in revised form 7 April 2016 Accepted 29 June 2016 Available online xxx Keywords: Rainwater harvesting Flood disaster Mitigation
a b s t r a c t Frequent inundation has become a serious problem in urban areas. It is necessary to improve rainwater retention/infiltration in the urban watershed. The purpose of this study is to report how private rainwater-retention/harvesting facilities can be spread gradually but steadily in the city by citizeninitiated activities. Rainwater harvesting tanks were installed intensively and a rainwater harvesting house was constructed in the city of Fukuoka, Japan after the city experienced a flood disaster. The former enhanced users’ daily preparedness for emergency, and the latter inspired construction of a rainwaterharvesting housing complex. A public elementary school is in use from April 2016, which is inspired by these facilities. The school premises are located on the land reclaimed from an old irrigation pond. Thus the school needs to be adapted to this condition. 3000 m3 of rainwater can be retained within the premises. The amounts of retention and discharge are monitored, and the data is utilized for science education. In big cities, people tend to depend too much on the top-down, mega-system, which invites more impervious surfaces in urban areas. Bottom-up, individual/collaborative approaches should be adopted in order to achieve multiple purposes of preventing/mitigating disasters, preserving/conserving ecosystems and nurturing/rebuilding communities in the city. © 2016 Elsevier Ltd. All rights reserved.
1. Introduction A river is indispensable for sustaining a quality environment for diverse forms of life whereas it becomes a source of trouble with the overabundance of water. Frequent inundation has become a serious problem in urban areas all over the world (WMO/GWP, 2008). This is because the impervious surface covers most of the city area, and rainfall in the city tends to intensify due to heat-island effect and global warming. Measures such as dredging rivers, strengthening drainage systems and constructing flood walls are needed (Muller, Biswas, Martin-Hurtado, & Tortajada, 2015); however, they drastically change the urban riverine ecosystem (Palmer, Liu, Matthews, & Mumba D’Odorico, 2015). Moreover, these public works are insufficient as the urban-flood disaster inevitably deteriorates without decreasing runoff per se. It is necessary to devise and implement effective measures for rainwater retention and infiltration within
∗ Corresponding author. E-mail addresses: [email protected] (S. Yamashita), [email protected] (R. Watanabe), [email protected] (Y. Shimatani).
the entire urban watershed where there are usually a huge number of private properties and enterprises situated. Furthermore, restoring the hydrologic cycle by utilizing the green infrastructure can be cost-effective and lead to a relevant policy change even in a metropolis like New York (NYC, 2014). In order to promote green infrastructure effectively, it is crucial to use a wide range of combinations of innovative rainwaterharvesting measures, rather than focusing on single innovations (Marsalek and Schreier, 2009). Moreover, accurate design and configuration, simulation, localization and imposing proper maintenance schemes are indispensable in executing the rainwater harvesting system (GhaffarianHoseini, Tookey, GhaffarianHoseini, Yusoff, & Hassan, 2015). This study reports private, small- to mid-sized rainwater harvesting tools/facilities installed in urban watersheds and their impacts on the public, flood-disaster mitigation. It also shows a large-sized facility constructed in another watershed. The facility has not only a rainwater-retention function but also ecological and educational roles. This study compares the facilities’ functions with each other and examines their effectiveness as rainwater harvesting systems.
http://dx.doi.org/10.1016/j.scs.2016.06.027 2210-6707/© 2016 Elsevier Ltd. All rights reserved.
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Fig. 1. Study sites.
The purpose of this study is to report how private rainwaterretention/harvesting activities can be spread gradually but steadily in the city, as a citizen-initiated, smart way to responding to urban flood-disaster risks in Japan. 2. Scope In this study, we deal with rainwater retention/harvesting tools/facilities in the city of Fukuoka (population: 1.53 mil.; area: 340 km2 ), Japan and its suburbs: Itoshima (97,000; 216,km2 ) and Shingu (29 000; 19 km2 ). First, we are focused on the Hii River Basin located within Fukuoka (Fig. 1). The lower areas in the watershed have experienced inundations three times since 1960. The latest took place in 2009, and just after this event, a citizens’ alliance for flooddisaster management was established (Yamashita et al., 2013). This group consists of a wide variety of stakeholders including victims of the disaster, residents in general, academics and college students studying watershed management, NPO members involved in water resources management, construction engineers, local government officials, etc. They have been trying to come up with ideas to tackle urban water challenges and practice what they can do together for a comprehensive flood control. Second, we move onto Itoshima and Shingu, both of which need to respond to a growing population as suburbs of Fukuoka (Fig. 1). In association with the activities for the Hii River Basin, an apartment complex featuring rainwater-harvesting facility was built in 2012 in Itoshima, and a public elementary school with rainwater retention/harvesting functions is in use from April 2016 in Shingu. In this study, we explain what the philosophy of these facilities is and how they are relevant to one another. 3. Citizens’ alliance for the Hii River Basin management 3.1. Hii River Basin and flood disaster in 2009 The watershed area of the Hii River is included within the Fukuoka city area (population: 1.53 mil.), which is located in the north of Kyushu, one of the main islands of Japan (Fig. 1). The area of the watershed is relatively small; it is only 29 km2 , and the length of the main channel is 13 km. The urbanized areas account for about 70% of the watershed area, and about 180,000 people live there. Three areas close to the Hii River were inundated due to heavy rainfall on July 24th, 2009. The rainfall was so intense; its amount reached about 100 mm/h. As the drainage system of the area is
designed to manage the rainfall intensity of up to 52 mm/h, it was naturally overwhelmed. The rapid and concentrated runoff due to urbanization made the inundation even worse; 410 houses were flooded within this small watershed (Fig. 2).
3.2. Citizens’ alliance In response, we decided to provide a new forum for citizens including local residents, local officials, businesses, engineers, students, academics, etc. to share views regarding floods and flood prevention/mitigation. As there are many kinds of stakeholders involved in this endeavor, all they need is to put aside their differences and work together to solve the problem. The group call themselves “Citizens’ Alliance for the Hii River Basin Management.” In order to share views and come up with voluntary runoffcontrol measures, the group carries out forums and fieldworks by themselves. The forums have been held 43 times from October 4, 2009 up until May 25, 2015. Around 100 people have participated in each forum. The 43 forums can be classified into six phases: 1) Introduction, 2) Development, 3) Technical recommendations, 4) Actions, 5) Involvement in drawing up the river development project, and 5) Safety plan for 100 mm/h-rainfall.
3.2.1. From introduction to technical recommendations During the period from the Introduction to Technical recommendations phases, the Alliance tried to build consensus and come up with ideas for comprehensive flood control. In the Introduction phase (Oct. 2009–Jan. 2010), the Alliance discussed and compiled recommendations and proposals for the comprehensive flood control and watershed management of the Hii River and submitted them to the mayor and governor of Fukuoka. In the Development phase (Feb.–Dec. 2010), NPO and student members of the Alliance took advantage of the prefectural monitoring system for rainwater harvesting and started to install rainwater retention/harvesting tanks (0.2 m3 ) to households willing to use one for free. The activity led most participants, including those who had experienced inundation and demanded immediate preventive measures, to agree to incorporate multiple rainwater retentions into flood control as an essential measure. In Technical recommendations phase (Jan.–May 2011), experts proposed redesigns of a closed schoolyard and an irrigation pond for effective rainwater retention/infiltration in the watershed and explored the possibility of constructing a rainwater harvesting house as a model housing
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Fig. 2. Three areas (Torikai, Tajima and Nagao) are inundated in the Hii River Basin (left). Over 20 mm/10 min rainfall was observed at 7pm on July 24, 2009 (upper right), and the river water overflowed (lower right).
project in the watershed (these three phases and part of the Actions phase are described in detail in Yamashita et al., 2013). 3.2.2. Actions (Jun. 2011–Mar. 2013) In the Actions phase, the Alliance tried to implement what they could do to prevent/mitigate flood disasters as individual and communal efforts. They carried out an awareness building workshop for children and promoted individual runoff reduction among the next generation in the future, participated in a traditional rejuvenation event of one of the irrigation ponds and decided that they would create “Hii-Kawa Gakko (Hii River School)” to promote runoff reduction among younger generations (Yamashita et al., 2013). Moreover, the Alliance initiated the design and implementation of risk management measures. For instance, recorded flood depth signs were installed in the inundation area of July 2009 Fukuoka flood (Fig. 3). The residents and college students took part in sign-design workshops in 2013. The workshops took into consideration both legibility and aesthetics as the sign were not only to be looked at just before flooding but also to be seen daily by both residents and visitors in the city. In addition, participants selected the color in the sign indicating the recorded flood depth to correspond to that in the inundation hazard map that had already been distributed by the city government in 2010. Thus they took care of the sentiment of those who had feared a decline in the land prices. In association with a ward office of the city government of Fukuoka, the Alliance devised a guidebook for evacuation when/before heavy rainfall and distributed it in March 2013 for the residents of Tajima, one of the inundated areas (Figs. 2 and 4). Workshops were carried out both for devising the guidebook and for explaining it to those who were concerned about flood-disaster risk management. This activity led to similar ones in other inundated areas, Torikai and Nagao (Fig. 2), in the Hii River Basin. Educational materials were deigned to nurture public awareness for flood-disaster risk management from early on. A local folklore/myth, which involved a giant, eight-necked serpent representing the river and flood disasters and a god/goddess symbolizing flood-disaster risk management, was incorporated in the design of a file folder to be used by children (Fig. 5).
Fig. 3. Recorded flood depth sign installed in March 2013 in the inundation area of July 2009 Fukuoka flood (upper), and a sign-design workshop by residents and college students in December 2012 (lower).
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Fig. 4. Guidebook (front cover (left) and p.7) for evacuation in Tajima, one of the inundated areas of July 2009 Fukuoka flood in the Hii River Basin.
Fig. 5. A file folder (left) and playing cards both designed for children to learn flood-disaster risk management. The cards are used at flood disaster risk management drills involving children (right).
Playing cards were also designed for children to learn importance of rainwater harvesting with pleasure. The messages in the cards were discussed in the forums and workshops by the Alliance, and the images in the cards were designed by college students studying child education based on the messages. The cards have been used in flood disaster risk management drills where children participate (Fig. 5). The rainwater harvesting house that had been discussed in the Technical recommendations phase was constructed in the watershed in May 2012 in the Actions phase. 3.2.3. Involvement in drawing up the river development project (May 2013–May 2014) The prefectural government of Fukuoka published the “Hii River System Development Project” in May 2014 (Fukuoka Prefectural Government, 2014). The project is stipulated by River Act of Japan and referred to for 30 years from publication. In the process of drawing up the plan, the local government needed to incorporate public comments into it. As they have been collaborative with the Alliance from the beginning, they attended the forums and explained the draft to the participants in January 2014. In response, the alliance provided over 100 comments on the draft, which were taken into consideration by the government revising the draft.
As a result, two significant revisions were made in the plan: 1) A registration system called “safety plan for 100 mm/h-rainfall,” a scheme for preventing and mitigating inundation caused by extremely heavy, short-term rainfall (such as 100 mm/h-rainfall) is written clearly in the clauses of the plan as a set of measures for runoff reduction, and 2) when the safety plan is established before long, the river development project can be revised in less than a decade, which is the period originally set for a possible readjustment of the project. The description of the safety plan for runoff reduction in the legal river development project is quite unique and rare as it requires administrators of the river and storm-water drainage system to cross-sectionally collaborate. 3.2.4. Safety plan for 100 mm/h-rainfall (Jul. 2014–May 2015) The system of “safety plan for 100 mm/h-rainfall” was established in April 2013 by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT, 2014). This has much to do with one of the policies the Japanese government has implemented to tackle flood disasters especially in urban areas in a comprehensive way since the late 1970s (MLIT, 2010). The plan is intended to mitigate food damage in urban areas not only by improving river channels and drainage systems but also
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by installing rainwater retention/infiltration facilities/functions all over the urban river basin. It expects river and drainage-system administrators, residents and private firms to collaborate and mitigate flood disasters by reducing surface runoff and sharing safety/risk information. MLIT requires potential municipalities to incorporate the following three aspects into their plan: • The targeted rainfall intensity must be greater, more local and shorter-lasting than the intensities set in both the legal river development project and storm-water drainage project. • River and drainage-system administrators, residents and private firms must work collaboratively and mitigate flood disasters by reducing surface runoff and sharing safety/risk information. • Measures focused on flood-damage reduction must be emphasized. The municipalities registered include the city of Nagoya, a metropolis (population: 2.28 million), and nine mid- to small-sized cities registered as of the end of December 2014. In Fukuoka, the Citizens’ Alliance for the Hii River Basin Management is collaborating with both the city and prefectural governments for drawing up the safety plan. The members of the Alliance find it indispensable to objectively demonstrate how effective it is to reduce runoff by individual and communal activities, and how those efforts are spread in wider urban areas, in order to materialize the safety plan in Fukuoka and to revise the Hii River System Development Project in the near future. In the following sections, we would like to address a wide variety of rainwater retaining/harvesting/infiltrating facilities installed not only in the Hii River Basin but also in nearby urban areas and show how they are relevant to each other.
Fig. 6. Rainwater retention/harvesting tank (0.2 m3 ).
Table 1 Categories and items of the questionnaire. Category
Item
Attribute
Address Family Initiative
Use
Knowledge on the campaign Purpose Usage Rainfall-information gathering Discharge before heavy rainfall Change in water charge Favorable feature
Awareness
Preparedness for rainfall Promotion/recommendation
Function
Design Needed capacity Price Operation Prior means for retention Water quality Publicity
Greening
Amount Intent of increasing green and the reason
4. Private tanks 4.1. Rainwater-harvesting tank Small- to mid-sized rainwater retention tools/facilities have been installed in the Hii River Basin since 2009. Naturally, just after the disaster in 2009, the victims did not pay much attention to rainwater retention but demanded immediate and direct measures involving larger rainwater pumping/discharge systems and higher floodwalls. They accused the local governments of having not taken effective measures. At first, it thus seemed quite difficult to build consensus for runoff reduction among the citizens involved (Yamashita et al., 2013). However, the tide turned after the NPO and college students intensively installed rainwater harvesting tanks (Fig. 6) for free (the tanks were provided by local governments) for the residents including the victims in 2010 (Section 3.2.1). Afterwards (Oct.–Dec. 2010), we carried out a questionnaire survey for the residents (96 households) who had the rainwaterharvesting tanks installed (106 tanks) and inquired about their attitudes toward the rainwater management (Table 1). The response rate was 86.5% (83/96). As a result, in terms of runoff reduction, it is found that flood-disaster mitigation/prevention is not considered to be the major reason for the users to retrofit the barrel; using rainwater for gardening etc. (54%) tops the list of the purposes, followed by water-saving in general (35%) and flood-disaster mitigation/prevention (9%). However, most of the users of the tank (82%) became more aware of the frequency and intensity of rainfall after they started to use retained water for gardening etc. (Fig. 7). 95% of them told their neighbors about advantages of the tank and recommended installation. 68% of the users replied that they would have gotten one even if it had not been free. The users attitudes
Fig. 7. Tank users’ awareness for heavy rainfall.
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Fig. 8. Rainwater-harvesting house. The blue of the plan (right) represents the cisterns (42 m3 in total).
Fig. 9. Rainwater harvesting from Jun. 2012–Dec. 2013. (a): water balance; (b): consumption/infiltration.
Fig. 10. Rainfall/discharge Aug. 30, 2013. At 14:00, rainwater was discharged into the storm-water drain.
implicate their enhanced daily preparedness for emergency, which is essential for an effective disaster evacuation. 4.2. Rainwater-harvesting house As the capacity of rainwater-harvesting tanks distributed in the watershed of the Hii River is 0.2 m3 , and the number of the tanks installed was only 106 at that time, their substantial function for runoff reduction is quite limited. The Alliance thought they needed to develop rainwater retention/harvesting as a housing system and demonstrate it to the public. As mentioned in section 3.2.2, a rainwater-harvesting house was constructed in 2012 in the Hii River Basin (Fig. 8). The owner of
the house is a member of the Alliance. The cisterns of the house retain about 42 m3 of rainwater and cost about \4,000,000. The unit cost is as low as a sixth of a big rainwater-storage (60,000 m3 )/discharge system established in 2012 by the city government of Fukuoka in another watershed (Fukuoka City Government, 2012). The rainwater retained is used domestically, and the amounts of input-output are closely monitored. Fig. 9 shows how the rainwater had been either used by the family or infiltrated into the soil during the period from Jun. 2012 to Dec. 2013. Around 50% of the rainfall in total was used domestically for flushing toilet, washing, bath etc., and the remainder seeped into the ground.
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nal garden, toilet and air conditioning. The input/output to/from its cistern is also closely monitored. Real-time data have been open to the public since Oct.19, 2014, and they can be accessed online without restriction (Moriyama). The structure of the cistern is unique; it is filled with crashed stones to sustain the structure, and the walls and the bottom are made of plastic. Thus the cistern is not so expensive. The unit cost is about \31,000/m3 , which is a third of that of the rainwaterharvesting house in the Hii River Basin. 6. Smart school
Fig. 11. Mid-sized retention/harvesting housing complex.
In August 30, 2013, the facility experienced a heavy rainfall, and its peak rainfall intensity was 33 mm/10 min around 2 p.m. (Fig. 10). The rainfall inundated the downtown area of Fukuoka, and the inundation occurred down the hill where this house is located (15-min walk). However, the cistern of the house dealt with the rainwater effectively, and it spilled just 1 m3 of water in total from the storm-water infiltration inlet to the drainage during the peak rainfall around 14:00 (Fig. 10). It should also be noted that this is the only discharge (1 m3 (discharge)/400 m3 (rainfall)) to the public drainage during the period of 1.5 years from the start of the observation in Jun. 2012–Dec. 2013 (Fig. 9). 5. Communal cistern and garden In order to promote runoff reduction in the Hii River Basin, we need to develop a wide variety of private housing systems featuring rainwater retention/harvesting. The rainwater-harvesting house inspired the construction of a housing complex that has a function of rainwater harvesting in the adjacent city of Itoshima (Fig. 11). The complex was so popular that its apartments were sold out soon after sale in May 2012. The complex can retain over 100 m3 of rainwater (Fig. 12). The water is provided for its commu-
As for large-sized runoff reduction systems, we have helped to develop an effective combination of turf and pervious soil for a football field since before 2009 (Yamashita et al., 2013). A public elementary school is open from April 2014 by another, nearby municipality, the town of Shingu, inspired by the installation of the above-mentioned, small- to mid-sized rainwater-harvesting facilities. The knowledge from the football field construction is integrated into the new school facilities as well. The school premises are located on the land reclaimed from an old irrigation pond that had been left behind in the urbanizationdesignated area. Naturally, the land and surrounding areas allocated for residency are prone to inundation. It is thus necessary for the school to be adapted to this condition. 1600 m3 of runoff from the surrounding residential areas can be retained within the schoolyard, under which two rainwaterretention cisterns are installed. One of the cisterns (1000 m3 ) is also to retain rainwater from the surrounding areas whereas the other (200 m3 ) is to collect rainwater that is fallen on the schoolyard and used afterwards to water the lawn covering the ground (Figs. 13–15 ). The 1,000 m3 -detention cistern costs about \60,000/m3 , twothirds of the unit cost of the rainwater-harvesting house in the Hii River Basin. The same type of pervious soil used for the football field is utilized as foundation for the schoolyard. The school buildings also has another 200 m3 -cistern to retain rainwater fallen on the facilities. In the earlier planning stages, an architect recommended that the cistern be smaller (40 m3 ) and installed above ground level for generalized, maintenance reasons. However, as the school board learned that both the rainwater har-
Fig. 12. Cistern of the complex (>100 m3 ). By courtesy of Daiken.
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Fig. 13. Rainwater-retention system of an elementary school (3800 m3 in total).
The school had two more challenges to overcome: it faces railroads and factories. Without proper design and configuration of the facilities, noise and smoke would be a problem. Thus, it has been decided that 1) the gymnasium and its sound absorbing green walls are located close to the railroad to buffer classroom buildings from train noise; 2) parking lots distance them sufficiently from the factories; and 3) the courtyard is arranged to function as a seasonal-wind corridor for air exchange (Fig. 16). In designing and planning the school, the challenges reminded us of Katsura Detached Palace in Kyoto. This imperial villa was constructed in the alluvial plane along the Katsura River. The location gave it the advantage of bringing water from the river for attractive garden ponds but also created the risk of flooding (Morimoto, 2011). By smartly adapting to the risk–giving the main building a high floor and surrounding the palace with bamboo fences to reduce damage from flooding, this beautiful palace has been in harmony with nature for around 400 years (Morimoto, 2011). It is hoped that pupils would learn how their school is smartly adapted to the risks, and that they would take pride in attending this school. The project is thus called “Smart School Project”.
7. Comparison
Fig. 14. Perspective of the school under construction from November 7, 2014.
vesting house in Fukuoka and the housing complex in Itoshima had caused no major maintenance problems for over one and a half years, they decided to increase the capacity of the cistern and install it underground. The rainwater retained is used to flush the toilet etc. when water lifeline is disrupted by disasters and to water flowers to be grown by pupils. The rainwater-reuse system in the building is powered by photovoltaics. The water is also used for a school biotope to be built. The amounts of retention and discharge will be monitored, and the data will be utilized for science education.
Architectural Institute of Japan (2016) published “Technical Standards for Rainwater Harvesting (AIJES-W000-2016)” in March 5, 2016, the first such standards devised for promoting comprehensive rainwater harvesting systems in Japan. This is to encourage both private and public sectors to participate in rainwater harvesting systematically. The standards take local hydrology/geology into consideration, which is critical for rainwater harvesting systems to be successful (Hering et al., 2015). The standards aim to retain up to a height of 100 mm of rainwater on average within a site area; the height is set based on the local precipitation data. The aspects of rainwater harvesting include 1) flood control, 2) daily water use, 3) emergency water use, 4) and environmental conservation; flood control and daily water use are to be directly linked to the targeted rainwater-storage height. Emergency water use is for people to endure without public water supply for up to three days (0.05 m3 × 3 days × #people), which is based on the experience in Tohoku on March 11, 2011. Rainwater retention for environmental conservation involves infiltration and evaporation features of the site. Table 2 shows the rainwater-harvesting functions of the singlefamily house in Fukuoka (Section 4.2), the housing complex in Itoshima (Section 5) and the elementary school in Shingu (Section 6) utilizing the standards. The total heights of rainwater storage of the house and the school are 195.5 and 137.1 mm, respectively and exceed the targeted 100 mm-threshold. The flood-control function of the two facilities also surpasses the threshold (130.8 and
Fig. 15. Construction site Mar. 17, 2015. (a): groundwork; (b): preloading for schoolyard; (c): inlet for 1000 m3 -cistern.
Please cite this article in press as: Yamashita, S., et al. Smart adaptation activities and measures against urban flood disasters. Sustainable Cities and Society (2016), http://dx.doi.org/10.1016/j.scs.2016.06.027
Housing complex
Elementary school
Total site area Rooftop Vegetation Permeable pavement Impervious pavement Pond etc. Schoolyard (soil) Schoolyard (turf) Others Infiltration rate Flood control storage tank capacity for the premises Flood control storage tank capacity for neighborhood Stormwater reservoir Cistern capacity (water use) Occupant Visitor Refuge User (total) Domestic use (flashing toilet/washing, etc.) Watering plants (turf/lawn, etc.) Water use (total)
100 100 297.91 105.72 192.21 – – – – – – 0.033 22.5 – – 19.3 4 – – 4 0.24 – 0.24
100 100 2700 955 345 600 – 15.4 – – 784.6 0.065 – – – 116.49 50 – – 50 1.5 3.5 5
100 100 20,113.17 5,765.30 1,000.00 – 6,371.87 – 3,603.50 3,372.50 – – – 1000 1600 400 900 – 100 1000 – 43.7 43.7
B. Flood control (mm)
Rooftop Vegetation Permeable pavement Impervious pavement Boardwalk/wood deck, etc. Schoolyard (soil) Schoolyard (turf) Stormwater reservoir Storage height for flood control by tank Storage height for flood control (total)
3.55 51.6 – – – – – – 75.5 130.76
4.4 10.2 10 – 1.9 – – – – 26.7
2.9 4 – 3.2 – 14.3 13.4 79.5 – 117.2
C. Daily rainwater use (mm)
Storage height for water use
64.8
43.2
19.9
D. Emergency water use
Water supply for emergency (m3 ) Storage height for emergency (mm)
– –
2.8 2.78
150 7.46
E. Environmental conservation (mm)
Storage height for environment
55.3
26.7
37.8
F. Total rainwater storage height (mm)
F=B+C
195.5
69.9
137.1
G. Deficit (mm)
G = A–F
−95.5
30.1
−37.1
H. Rainwater Storage ratio (%)
H = F÷A × 100
195.5
69.9
137.1
Calculation condition
a. Basic storage height (mm) A. Storage height aimed within the premises (mm) Surface condition (m2 )
Infiltration (m3 /h) Storage facility (m3 )
User (#person)
Rainwater used (m3 /day)
ARTICLE IN PRESS
Single-family house
G Model
SCS-461; No. of Pages 10
Building use
S. Yamashita et al. / Sustainable Cities and Society xxx (2016) xxx–xxx
Please cite this article in press as: Yamashita, S., et al. Smart adaptation activities and measures against urban flood disasters. Sustainable Cities and Society (2016), http://dx.doi.org/10.1016/j.scs.2016.06.027
Table 2 Rainwater-harvesting functions of the single-family house in Fukuoka, the housing complex in Itoshima and the Elementary school in Shingu based on “Technical Standards for Rainwater Harvesting (AIJES-W000-2016)”.
9
G Model SCS-461; No. of Pages 10 10
ARTICLE IN PRESS S. Yamashita et al. / Sustainable Cities and Society xxx (2016) xxx–xxx
Fig. 16. Configuration for the school facilities to adapt to the challenges of flooding, noise and smoke.
117.2 mm, respectively). The capacities for daily rainwater use of the two housing facilities are way greater than that of the school, whereas the school can serve more than 1000 people without public water supply for up to three days by the 200 m3 -cistern installed under the gym. The environmental conservation function of the facilities are also considerable (house: 55.3 mm; complex: 26.7 mm; school: 37.8 mm). The construction costs of the tanks installed in the house, the housing complex and the school are around 1/6, 1/12 and 1/9 of that of the above-mentioned municipal flood-control reservoir, respectively. Thus, it may be fair to say that these three facilities are cost-effective compared to the municipal gray infrastructure. 8. Concluding remarks As we saw in the previous sections, individual/collaborative approaches are cost-effective, ecofriendly and thus sustainable. In Fukuoka and its suburbs, installing small-/mid-sized rainwaterharvesting tools/facilities and the monitoring data have encouraged the public to get involved more in urban-runoff reduction. It is clear that taking small steps surely leads to safeguarding the city from flood disasters. Smart adaptation to flooding should be a prerequisite for the restoration of a sound hydrologic cycle in the city, and urban biodiversity in the long run. In big cities, people tend to depend too much on the top-down, mega-system involving dredging rivers, strengthening drainage systems, constructing flood walls, etc., which invites more manmade, impervious surfaces in urban areas. Even the city with its safety plan for 100 mm/h-rainfall leans toward mega-systems for runoff reduction. For instance, the city of Nagoya, Japan, which has implemented its registered safety plan since 2013, puts emphasis not on private efforts for runoff reduction but on large-sized rainwater retention/infiltration. In the watersheds targeted in Nagoya’s safety plans, there are large-sized public rainwater retention facilities installed that can retain 233,500 m3 of rainwater in total but no subsidy program for small-/mid-sized, private rainwater retention/harvesting tanks (MLIT, 2014). On the other hand, flood-disaster risks increase with excessive dependence on public works, as we have learned from the tsunami disasters in Tohoku (Hirano, 2013; Nakai, 2013).
Bottom-up, individual and/or collaborative approaches should be adopted in order to achieve multiple purposes of preventing/mitigating disasters, preserving/conserving ecosystems and nurturing/rebuilding communities in the city. We need to become more sensitive to hydrologic cycle by utilizing appropriate technology, and thus smartly adapt to flood- disaster risks in the city. References Architectural Institute of Japan. (2016). Technical standards for rainwater harvesting (AIJES-W000.-2016. In japanese with English summary). Tokyo: AIJ. Fukuoka City Government. (2012). Rainbow Plan Hakata. Fukuoka: Fukuoka City Government. http://www.city.fukuoka.lg.jp/doro-gesuido/keikaku/hp/ usuiseibirainbowplanhakata 1.html Fukuoka Prefectural Government. (2014). The Hii river system development project (in Japanese). Fukuoka: Fukuoka Prefectural Government. GhaffarianHoseini, A., Tookey, J., GhaffarianHoseini, A., Yusoff, S. M., & Hassan, N. B. (2015). State of the art rainwater harvesting systems towards promoting green built environments: a review. Desalination and Water Treatment, 1–10. Hering, J. G., Sedlak, D. L., Tortajada, C., Biswas, A. K., Niwagaba, C., & Breu, T. (2015). Local perspective on water. Science, 349(6247), 479–480. Hirano, K. (2013). Difficulties in post-tsunami reconstruction plan following Japan’s 3.11 mega disaster: dilemma between protection and sustainability. Journal of JSCE, 1(1), 1–11. Marsalek, J., & Schreier, H. (2009). Innovation in stormwater management in Canada: the way forward, overview of the theme issue. Water Quality Research Journal of Canada, 44(1), v–x. MLIT (Ministry of Land, Infrastructure, Transport and Tourism). (2010). Comprehensive flood control: effectiveness of the act of flood-disaster measures for designated urban rivers (in Japanese). Tokyo: MLIT. MLIT. (2014). Safety plan for 100. http://www.mlit.go.jp/river/kasen/main/100mm/ Morimoto, Y. (2011). Biodiversity and ecosystem services in urban areas for smart adaptation to climate change: do you Kyoto? Landscape Ecological Engineering, 7, 9–16. Moriyama, T. http://srtmonitor-env.elasticbeanstalk.com/ monitor?token=531c5aabe85c6 Muller, M., Biswas, A., Martin-Hurtado, R., & Tortajada, C. (2015). Built infrastructure is essential. Science, 349(6248), 585–586. Nakai, Y. (2013). Reconstruction plan of Otsuchi town, Kamihei county, Iwate prefecture. Journal of JSCE, 1(1), 242–250. NYC Environmental Protection. (2013). NYC green infrastructure: 2013 annual report. New York: NYC Environmental Protection. Palmer, M. A., Liu, J., Matthews, J. H., & Mumba D’Odorico, P. (2015). Manage water in a green way. Science, 349(6248), 584–585. World Meteorological Organization and Global Water Partnership (2008). Urban Flood Risk Management—A Tool for Integrated Flood Management, Associated Programme on Flood Management. Yamashita, S., Shimatani, Y., Watanabe, R., Moriyama, T., Minagawa, T., Kakudo, K., et al. (2013). Comprehensive flood control involving citizens in a Japanese watershed. Water Science & Technology, 68, 791–798.
Please cite this article in press as: Yamashita, S., et al. Smart adaptation activities and measures against urban flood disasters. Sustainable Cities and Society (2016), http://dx.doi.org/10.1016/j.scs.2016.06.027