Exploring Urban Flood Policy Trends Using a Socio-Hydrological Approach—Case Studies from Japanese Cities

Abstract

Most industrialized nations have attempted to control floods through civil engineering technologies. However, these measures have failed in the face of immense natural forces. Through allomorph analysis and expert interviews, this study examined the situation of implementing urban flood rules in major Japanese cities. The river canal in the Tokyo region is mostly maintained through infrastructure, and Tokyo has a diverse network of systems linked by rivers, canals, and drainage channels, which demonstrates its dominance in structural and civil engineering flood management. In Osaka Prefecture, flood risk management is an ongoing process built on a structural engineering foundation, and local governments continue to examine and update new policies to handle the risks and difficulties produced by ever-changing flood catastrophes. To enhance public education and awareness, local administrations in the Toyama and Chiba Prefectures are implementing programs to educate locals about flood hazards and preparation. To summarize, public engagement is an important component of flood risk mitigation and management in Japanese communities. Governments may help communities become more resilient and prepared in the face of floods by involving local residents, institutionalizing public education and awareness, and building volunteer networks. This is the conclusion reached as a result of socio-hydrological intervention.

1. Introduction

1.1. Background

Natural catastrophes have traditionally shaped Japanese cities’ spatial culture [1]. Among the natural calamities faced by Japanese cities, flooding has been the most difficult to overcome in the history of urbanization [2]. Even as civilization and civil engineering technology have advanced, floods have not been entirely controllable. Most advanced countries, including Japan, have attempted to mitigate them through architectural engineering technology to date [3]. However, these measures have failed in the face of immense natural forces, and flood damage has not been decreased despite the effects of urbanization. Socio-hydrology (SH) is a relatively young multidisciplinary field that tries to explain the intricate relationships between social systems and water systems, giving a tool for demonstrating the relationship between floods and cities in a variety of ways [4]. It is plausible to hypothesize that a significant proportion of fatalities associated with flooding are attributed to individuals who engage in deliberate risk-taking behavior by intentionally coming into contact with floodwaters [5]. As a result, the purpose of this research was to determine the flood control policy implications of Japanese cities using an SH method.

Socio-hydrology (SH) is a method of studying the effects of water (water resource systems) on people and the effects of people on water [6]. This research discovers significant changes in the aquatic ecosystem and looks at numerous issues, such as nature, society, and politics, to understand how people utilize and manage water-related resources in urban society. SH is a specific convergent subject that explores how people make decisions about water resources and the effects of natural disasters, such as floods and droughts, on communities [7]. Socio-hydrologists examine water-related difficulties using both social science and engineering, attempting to create a solution that will allow everyone to have equitable access to adequate water and keep safe from water disasters [8]. SH is especially significant in the context of global environmental changes, since human activities increasingly impact water resource consumption and distribution [9]. Climate change, land use change, and population increase are all variables that can affect water supply and quality, and SH investigates how these changes affect water systems and water-dependent urban inhabitants, as well as providing sociotechnical solutions [9].

Japanese cities use innovative engineering techniques to manage water resources and catastrophes [10]. However, it is now vital to look at water-related tragedies from a different angle. As a result, this study analyzed each city’s flood policy direction (政向), which is an important approach for SH research. Four key Japanese cities (Tokyo (東京), Osaka (大阪), Chiba (千葉), and Toyama (富山)) were chosen, and numerous legislative planning papers were evaluated using an SH coding table. Following that, expert interviews (semi-structured) were conducted. No scholars have performed studies of SH orientation using cases of Japanese cities, and it is predicted that this will contribute to the creation of an SH flood control system that decreases damage in the event of future floods.

1.2. What Is Socio-Hydrology (SH)?

SH is defined as comprehending and interpreting the feedback system between human activities and water resources [11]. Since the 1970s, researchers have attempted to explain the connection between the hydrological system and human activities, and this is known as hydrological sociology or SH, which is classified under the term socio-ecological systems (SESs) [12]. The connection between humans and natural systems is referred to as SESs [13]. SH is sometimes defined as the comparative study of the co-evolution and self-organization of human and water systems across cultures, as well as the process-based structural modeling of coupled human–water systems [14]. SH primarily aims to understand the resilience and sustainability of watershed and river basin communities [15]. As a result, SH can provide a valuable framework and standard for studying river destruction caused by human activity in rivers. Successful river management may be depicted as an effective interaction between social and ecological systems inside the stream (i.e., as a detailed sub-section of SESs) [16]. We should grasp how to incorporate the aquatic environment with societal ideas in this part.

Human activities are often defined as boundary conditions for water systems or as external pushing elements in conventional hydrology [17]. Most hydrological research initiatives based on standard scientific and technical principles have limited long-term projections and are impracticable because they fail to capture interactions and two-way feedback between human and water systems [12]. Science engineering-oriented water resource management is usually dominant because many emerging countries need to develop the research and technology required for rapid economic development as they modernize and industrialize [18,19]. As a consequence, most countries do not pay attention to concepts related to the field of human–water interaction, such as virtual water systems. The concept of SH is central to efforts to combine water and human culture. Furthermore, while comprehending the co-evolution of the human–water system, SH must overcome the lack of knowledge about the relationship between people’s perceptions and water [14].

The term “hydrology” was used to define SH, which evolved from SESs. Sivapalan et al. [12] suggested that hydrology, a new science of people and water, is crucial to comprehending the dynamics and mutual evolution of the coupled human–water system. Falkenmark [13] pioneered hydro-sociology by studying human–water systems in modern science. SH is believed to have evolved from studying the basic function of water and the consequences of water-related demands based on socioeconomic development, population change, and future water needs [13]. The water problem is an essential variable in water sociology that defines future water management behavior [20].

Climate change is also a new component of hydro-sociology. As a result, this researcher regards “hydrological sociology” as an archaic word for SH. Sivakumar [21] pointed out that both hydrological sociology and the SH literature are derived from the same scientific and social literature on water issues and tasks examined by the hydrologic community, which investigates people’s water resource usage behavior.

This study applied the concept of “process-based SH” while reviewing Japanese cities through an allomorph analysis of the content of each Japanese city policy report for a clear understanding of SH within practical problems. Japan’s examples also demonstrated improvement through traditional structural strategies of flood control/prevention, as water quality and aquatic ecosystems have improved within temporal and geographical dynamics (integrated water resource management). Furthermore, in the river flood control process, these examples have a citizen-centered human–material mutual understanding framework, offering a new approach for future flood management.

1.3. Application of SH to Flood Management?

It is simple to uncover research trends among socio-hydrologists that stress the relevance of flood management governance. This may be viewed as an academic tendency to jointly describe the governance component, that is, all social variables associated with flood management and prevention, from the standpoint of comprehending flood management through social scientific considerations. Flood management governance is also defined as a decision-making process that comprehensively handles the conflict factors, approaches to flood damage, ecosystem services, and water resource-related legislation of all parties concerned [22]. SH at the flood management level is also employed in practical flood management domains such as more sustainable and large-scale water management policies and spatial planning, which consider social and environmental issues [23]. Overall, SH is an emerging field that recognizes the connection of human and environmental systems and promotes a more integrated and sustainable approach to flood control [15].

Because flooding is one of the most severe water-related threats to human society, SH is strongly linked to flood prevention management and the safety of human activities. Flood risk assessment, flood prediction and warning, and the creation of methods to decrease flood disaster risk and mitigate consequences are all part of flood prevention management [24].

SH can aid flood prevention management in various analytical methodologies. First, it can contribute to a better understanding of the various socioeconomic and environmental elements that conduce to flood risk [25]. For example, SH can be employed to investigate how land use changes, urbanization, and population increase influence the frequency and severity of floods, as well as how these variables interact with natural elements like climatic volatility and extreme weather events [26]. Second, SH may assist in identifying the social and economic consequences of floods, as well as how these consequences are dispersed among various areas and groups [27]. This can aid in the development of a more equitable and effective flood management policy that considers the needs and viewpoints of many stakeholders [28]. Third, SH can help to build more sustainable and adaptive flood protection measures that consider the dynamic and linked nature of human and environmental systems [29]. This might include measures like ecosystem-based flood management, which acknowledges the role of natural systems in lowering flood risk, or the use of innovative technologies, like early warning systems and flood modeling tools, to strengthen flood risk assessment and prediction [30].

2. Materials and Methods

This study team chose four major prefectures in Japan (Tokyo, Osaka, Chiba, and Toyama) and compared the policy trends among the examples through professional interviews with Japanese disaster specialists. Flooding and coastal catastrophes have historically wreaked havoc on all of these prefectures. At the same time, the prefectures represent various geographical traits and ecosystems on Honshu, Japan’s main island. The aim of this study was to answer the following research questions:

(1)

What is the meaning of SH in Japanese flood management policy?

(2)

What is the trend of flood mitigation policy in major Japanese cities?

(3)

How can we describe and differentiate each region’s flood risk mitigation policy direction?

In Japan, each prefecture issues new policy papers on topics such as urban, environmental, flood mitigation, and disaster prevention planning. First, our team gathered important data and papers connected to those planning documents using recently updated resources. Second, these materials were sorted into allomorph units for analytical advancement. Third, the flood prevention and management allomorph units were assessed using the coding matrix produced by the social-ecological-technological systems (SETS) learning framework [31]. This coding matrix is divided into the following categories: (1) social system–social institution, communication, normative/economic, (2) ecological system–ecosystem conservation, green infrastructure, ecological services, and (3) technological system–technical design, engineering infrastructure, and data analysis (climate change). The Dedoose qualitative research instrument was used to create this analytical framework.

3. Results

3.1. Case of Tokyo

Our researchers collected a total of 2118 codes from allomorph analysis with four major cases in Japan (Tokyo, Osaka, Chiba, and Toyama) and compared them.

Table 1. Tokyo coding results via SETS codes based on allomorph units (S1: Social Institution, S2: Communication, S3: Normative/Economy, E1: Ecosystem Conservation, E2: Green Infra., E3: Ecological Service, T1: Technological Design, T2: Engineering Infrastructure, T3: Data Analysis).

Tokyo	S1	S2	S3	E1	E2	E3	T1	T2	T3
Urban Plan	20	6	7	2	10	12	20	22	0
Environmental Plan	3	3	1	3	7	8	4	5	4
Flood Mitigation Plan	11	11	2	0	0	1	0	1	4
Disaster Management Plan	18	32	6	1	3	1	19	34	27
Total	52	52	16	6	20	22	43	62	35

below indicates the ratio of each section representing SETS. Tokyo shows the highest reliance on technological engineering in flood management. Because Tokyo, Japan’s capital, is densely populated and subject to flooding, flood risk management is highly critical. Tokyo’s low coastline location subjects it to severe rains, typhoons, and floods produced by storm surges [32]. The Tokyo Metropolitan Government is collaborating with numerous organizations to implement a number of flood-prevention measures. Documents on urban, environmental, flood mitigation, and disaster prevention planning recently published in Tokyo and used to create policy were coded, and several key aspects of flood risk management in the Tokyo area were elucidated after analyzing these SETS codes (S1: Social Institution, S2: Communication, S3: Normative/Economy, E1: Ecosystem Conservation, E2: Green Infra., E3: Ecological Service, T1: Technological Design, T2: Engineering Infrastructure, T3: Data Analysis).

To begin with, Tokyo manages a diverse network of river canals and drainage systems. In particular, the city has transformed the river basin into an urban region to control and avoid flooding. This might be due to the high population density and developed urban regions in the Tokyo area. The analysis results shown in Figure 1 demonstrate Tokyo’s dominance in structural civil engineering in flood management. These buildings must be evaluated and improved on a regular basis to guarantee their efficacy, which is why the facility management corporation’s tasks are regarded as critical (Table 1).

In the instance of Tokyo, the government has jurisdiction over a wide variety of river water management systems. To regulate the flow of water during heavy rains, Tokyo has a comprehensive river water system that involves the construction and maintenance of flood control infrastructure, including levees, sluices, and pumping stations. It has been determined that these structures are reviewed and improved on a regular basis to ensure their effectiveness.

To reduce the risk of urban flooding during heavy rains, Tokyo has established a public disaster law policy to regulate the flow of water in the case of floods and built a recharging reservoir in downtown Tokyo known as the “flood control reservoir” or “underground precipitation artificial recharging facility.” When the risk of flooding decreases, this artificial fluvial recharging facility temporarily stores additional water and eventually discharges it into the river water system.

Tokyo has a disaster early warning system that employs advanced weather monitoring technologies. The Japanese Meteorological Agency (気象庁) and the Tokyo Metropolitan Government have protocols in place to provide inhabitants with timely alerts and warnings via multiple communication channels, such as television, radio, mobile applications, and sirens. These alerts enable homeowners and residents to take proper precautions and evacuate if required. Indeed, in the case of a flood or typhoon, using the warning system is the quickest way to notify city dwellers of the threat. A warning system of this type has recently been developed using information and communications technology (ICT).

To estimate flood hazards, the Tokyo Metropolitan Government actively monitors weather patterns, riverine water levels, and precipitation projections. This was intended to be seen as demonstrating flood management qualities in representative ways, such as data analytic statistics and climate change [33]. These gathered data are evaluated to provide flood predictions, which help decision-makers make educated judgments concerning flood control activities and evacuation procedures.

Tokyo’s associated ministries have established a vision that includes green infrastructure components in urban design, such as parks, rainwater gardens, and water-permeable architecture, to increase the efficiency of natural drainage systems in the event of flood. These green areas absorb rainfall and minimize runoff to lessen flood hazards, and they contribute considerably to the vegetation covering urban and coastal regions.

Finally, Tokyo operates a public awareness program to educate inhabitants on flood hazards, evacuation methods, and emergency preparedness, with the goal of raising individual understanding and empowering citizens to take proactive measures to safeguard themselves and their property. Furthermore, it aims to enact policies while considering governance factors. Tokyo’s overarching goal is to collaborate with a wide range of partners, including local governments, water management agencies, and professional research institutions, to develop and implement comprehensive flood risk control measures. This is because such cooperation may enable the coordination of emergency response activities as well as the pooling of resources and experience. It should be noted that flood risk management in Tokyo is a continuous and dynamic activity. Tokyo, Japan’s heart, continues to invest in upgraded structural engineering infrastructure, technology advancement, and community engagement to improve flood resistance and ensure inhabitants’ safety and well-being.

3.2. Case of Osaka

Flood risk management in Osaka Prefecture, located in Japan’s Kansai area, is of particular significance due to its geographical vulnerability to floods [34]. Osaka is located in the Yodo River Delta, surrounded by rivers, canals, and coastal areas, leaving it vulnerable to severe rains, typhoons, and tsunamis. Local governments collaborate with numerous agencies and groups to undertake a variety of flood-prevention measures in the region. The following Figure 2 depicts the key features of flood risk management policy in Osaka Prefecture.

The Yodo River, which runs internally, is part of Osaka Prefecture’s large water network. Consequently, the analysis focuses on improving the warning system through the collection of data on aquatic ecosystems and rainfall connected to rivers. To regulate water levels and decrease flood dangers during heavy rains, the Osaka prefectural administration builds and maintains levees, floodgates, and pumping stations along rivers flowing through the region. Periodic maintenance and upgrades are chosen and carried out as the major objective of flood management prevention projects to ensure the efficacy of these structures.

Furthermore, efforts to enhance river channel and shoreline areas are being made to prevent the urban flooding of rivers in the water system. Moreover, investments in ongoing initiatives to broaden and deepen the riverbeds of the Yodo River and its tributaries are being made. These river water system development projects are designed to boost freshwater capacity in order to manage more water in the case of flood and lessen the danger of floods. Osaka Prefecture has proposed building an underground recharge reservoir, similar to Tokyo’s flood control facility, to hold excess water during heavy rains and gradually release it once the risk of flooding has passed. Such artificial recharging reservoirs serve to mitigate the damage and impact of urban flooding while also easing the pressure on the river environment. Unlike that of Tokyo, Osaka’s reservoir prioritizes green building (

Table 2. Osaka coding results via SETS codes based on allomorph units (S1: Social Institution, S2: Communication, S3: Normative/Economy, E1: Ecosystem Conservation, E2: Green Infra., E3: Ecological Service, T1: Technological Design, T2: Engineering Infrastructure, T3: Data Analysis).

Osaka	S1	S2	S3	E1	E2	E3	T1	T2	T3
Urban Plan	3	1	0	0	0	4	5	4	4
Environmental Plan	0	0	0	0	0	0	0	0	0
Flood Mitigation Plan	3	3	3	0	1	26	13	16	41
Disaster Management Plan	21	56	5	0	0	14	12	9	15
Total	27	60	8	0	1	44	30	29	60

).

As previously noted, the administration in the Osaka area has gathered flood data, swiftly alerted inhabitants, and created procedures to help individuals evacuate safely. Thus, Osaka Prefecture has been developing a sophisticated early warning system that integrates meteorological and river monitoring data to deliver timely flood warnings and alerts. A flood alarm is issued and distributed through multiple media, such as television, radio, mobile applications, and sirens, to inform citizens and aid evacuation if necessary. To reduce floods through river water system management, the Osaka prefectural administration created floodplain zone systems and land use laws. These laws permit the construction of new buildings in safe sites as well as the modification of existing structures to satisfy particular flood-resistant levels.

The Osaka prefectural administration has initiated a public awareness campaign to educate locals about flood hazards, evacuation protocols, and disaster preparedness. The aim of these programs is to persuade citizens to take proactive steps to protect their personal safety and property, as well as to offer information on how to respond in the case of flood.

Simultaneously, urban flood management governance is being formed to ensure citizen safety. In collaboration with numerous partners, such as adjacent municipal governments, water management organizations, and emergency response agencies, the Osaka Ministry developed and implemented a comprehensive flood risk management policy. These relationships enabled coordinated emergency response, data sharing, and the exchange of expertise. Flood risk management in Osaka, like in Tokyo, is an ongoing process built on a structural engineering foundation, and local governments continue to examine and update policies to address the risks and difficulties produced by ever-changing flood disasters. The area intends to strengthen resistance against floods and safeguard the well-being of its citizens by investing in structural infrastructure, technology and engineering development, community public education, and collaborative governance activities.

3.3. Case of Chiba

Chiba Prefecture, located in Japan’s Kanto area, is more interested in flood risk management than interior regions because of its coastal location. Chiba Prefecture is under constant threat from severe rains, typhoons, storm surges, and tidal floods. The Chiba prefectural administration collaborates with a variety of institutions and organizations to adopt various social and institutional initiatives to reduce the danger of flooding in the jurisdiction. Chiba City is working to strengthen its flood risk management policy to reduce the impact of urban floods and protect the safety and welfare of its citizens, as shown in Figure 3.

Chiba City, the capital of Chiba Prefecture, has suffered multiple major urban flooding incidents in the past. Because the city is located on the coast and is vulnerable to severe rains and typhoons, it must manage and mitigate the danger of flood damage. The 14th typhoon, Phyllis, struck Chiba City in September 1954, producing torrential rainfall and serious floods [35]. Typhoons have caused severe flooding in cities, particularly in low-lying neighborhoods and areas near riverbanks. Floods have caused significant property damage and affected the daily lives of the cities’ residents. Four years later, in September 1959, the ninth typhoon, Vera, slammed Chiba City and other regions of Japan, wreaking havoc and creating significant flooding. Typhoon-related rain inundated rivers, severely flooded low-lying regions, and damaged infrastructure and structures in Chiba City. The floods of 1959 caused fatalities and extensive property damage [36]. In addition, Chiba City experiences excessive rainfall annually, resulting in urban inundation. In recent years, there have been instances of excessive rainfall in the Chiba region, where urbanization has advanced significantly, resulting in the inundation of roads, homes, and infrastructure. Because of these incidents, the need to prevent heavy rains in advance and promote comprehensive flood risk management was addressed in depth when government regulations were developed. Chiba City implemented social engineering strategies to strengthen its flood risk management plan and boost resilience in response to historically continuous flood disasters.

Chiba Prefecture, located near the huge metropolis of Tokyo, contains a mix of urban, rural, and forest areas, as well as ports and airports that serve as Japan’s gateway. Chiba Prefecture’s social and institutional urban flood control strategy is primarily centered on public awareness and education. A network system has been built to disseminate information on various community field activities to enable both rural and urban inhabitants to cope with urban floods. The Chiba Prefectural Government and Fire Department, Chiba Prefecture’s administrative agencies, conduct public awareness programs to educate citizens about flood threats, evacuation methods, and disaster preparedness. These programs give accurate information on how to respond to floods, the significance of early evacuation in the event of flood warnings, and self-rescue tactics to safeguard life and property. Chiba Prefecture has formed governance and developed and implemented a comprehensive flood risk management strategy in collaboration with civic groups, water management groups, and emergency response agencies. Support for this collaboration enabling coordinated emergency responses, resource sharing, and the exchange of expertise has been invaluable for its urban flood control systems.

According to

Table 3. Chiba coding results via SETS (codes based on allomorph units).

Chiba	S1	S2	S3	E1	E2	E3	T1	T2	T3
Urban Plan	0	0	0	0	0	0	0	0	0
Environmental Plan	0	0	0	0	0	0	0	0	0
Flood Mitigation Plan	83	29	13	2	5	3	14	26	31
Disaster Management Plan	12	2	3	8	11	8	18	19	18
Total	95	31	16	10	16	11	32	45	49

, Chiba Prefecture is restructuring structural engineering solutions to avoid and lessen damage from urban floods. During severe rains, Chiba Prefecture has a huge network of drains and systems in place to collect and redirect excess water. These drainage systems are cleaned and maintained regularly to guarantee effective water flow and reduce the danger of urban floods. As such, it seeks to increase water flow and lessen the risk of urban floods by erecting coastal defenses and seawalls, as well as updating and maintaining drainage systems and drainage channels that connect rivers and beaches in a logical sequence. Breakwaters and coastal fortifications, for example, were created along the shore to protect coastal areas from storm surges and tidal floods. These structures mitigate the impact of high tide during floods and serve to avoid flooding in coastal regions. Chiba Prefecture’s flood management thoroughly addresses the features of coastal catastrophes.

3.4. Case of Toyama

Toyama, in central Japan, is an area prone to flood damage due to its location at the junction of many important rivers, notably the Jinzu and Sho Rivers. Toyama has created a thorough flood risk management program throughout the years to help limit the impact of floods on the city. It has recently advocated for an international effort to develop Toyama into a sustainable compact city based on the United Nations’ Sustainable Development Goals (SDGs) [37]. Through government document analysis, the policy direction for urban flood management and prevention in the Toyama area was schematized. The Toyama area has recently faced population/fertility reduction and multilingual socialization, and these variables have been projected in urban flood control and prevention programs, creating a platform distinct from other locations, as shown in Figure 4.

Toyama Prefecture in Japan is well known for its breathtaking beauty as well as its rich social and cultural history. Toyama is an important fishing port on Honshu Island’s west coast as well as a hub of agriculture and forestry. However, like many coastal locations, it is vulnerable to flooding due to geographical factors, particularly when faced with heavy rains and typhoons. As a result, flood risk management is a critical concern for local governments and communities.

Toyama Prefecture Authority is also making certain efforts to lessen the risk of floods. To summarize the primary components of Toyama’s flood risk management program, it intends to emphasize communication among social institutions as well as with the community and stakeholders. Toyama has a long history of community involvement and participation in flood risk control. The Toyama Prefectural Government and City Hall officials collaborate closely with local people and companies to create and implement flood risk management measures, as well as to encourage community engagement in disaster preparation and response operations. To that end, Toyama Prefecture initiated a government-led public education program on urban catastrophes to improve residents’ understanding of flood hazards and how to prepare for them. These advertisements address topics including emergency supplies, evacuation procedures, and flood insurance. Furthermore, the Toyama prefectural administration has prepared an evacuation plan that details safe sites for inhabitants to travel to in the event of flood and the routes they should take. To guarantee their success, these techniques are examined and updated twice a year.

In the instance of Toyama Prefecture, land use plans were formed to gather data linked to river flooding or pluvial flooding and share it with the community to avoid flooding damage and use flood water for agriculture or forestry in the community. Toyama has rigorous land use planning laws in place to reduce the danger of flooding by limiting development in flood-prone regions. It also developed green infrastructure initiatives to regulate rainwater runoff, such as rainwater recharging gardens and green roofs. Simultaneously, it has established a sophisticated disaster planning and response system, which includes early warning systems, evacuation plans, and emergency shelters comparable to those seen in other locations.

Toyama City, the prefectural capital, holds regular training sessions to assist citizens in preparing for probable flood catastrophes. In pursuit of the SDGs, Toyama City is also putting in place a policy to provide information on various disasters in the city in foreign languages to ensure the safety of immigrant communities who have migrated from abroad.

Pursuant to

Table 4. Toyama coding results via SETS codes based on allomorph units (S1: Social Institution, S2: Communication, S3: Normative/Economy, E1: Ecosystem Conservation, E2: Green Infra., E3: Ecological Service, T1: Technological Design, T2: Engineering Infrastructure, T3: Data Analysis).

Toyama	S1	S2	S3	E1	E2	E3	T1	T2	T3
Urban Plan	0	0	5	0	0	1	1	1	0
Environmental Plan	0	0	0	0	0	0	0	0	0
Flood Mitigation Plan	28	42	3	0	1	7	1	10	19
Disaster Management Plan	17	9	1	3	4	0	10	14	10
Total	45	51	9	3	5	8	12	25	29

, Toyama Prefecture has developed several river management methods that mitigate the risk of urban floods [38]. The local government has built a network of embankments, dams, and drainage canals to modify and regulate the direction of floods. This infrastructure is inspected and maintained regularly to ensure efficient flood management. This comprises yearly river canal maintenance, flood embankment building, and hydrological/hydraulic system installation. Overall, Toyama’s flood risk management program employs a comprehensive and integrated approach that combines physical measures, disaster preparedness and response, limited land use planning, and community participation to reduce flood risk and the impact on cities and residents through communication. Despite its vulnerability to flooding, Toyama Prefecture has not experienced severe floods recently, demonstrating the effectiveness of its flood response program.

4. Discussion

Given the harm caused by people in the development of natural ecological resources, it is critical to comprehend the successful integration of human activities and ecological systems in connection to natural resource management [39]. Because of the various uncertainties and complexities involved in the process, it may be claimed that the integration of human and ecological systems in terms of river flood control necessitates a new paradigm to allow communication between the two systems [40].

Flood prevention and management issues in Japanese cities may be addressed by using adaptive governance methods, as detailed in the SES and SH analysis. Huitema et al. [41] also emphasize the need for adaptive governance in dealing with the unpredictability and complexity found in SES, arguing that adaptive governance is effective in industrialized towns concentrated on research and technology. Most river management instances in Japanese cities in particular have tended to be biased toward science and technology-oriented management, which presents numerous challenges in terms of river flood management and prevention. Of course, hydrologic scientists (civil engineers) and engineers may be viewed as performing in-depth examinations of measurements and metrics of water quality standards to aid in the evaluation of successful flood management during the rainy season. However, in the past, conventional river flood control was ineffective in the absence of suitable governance-building initiatives [42,43].

Integrated water resources management (IWRM), another subtype of SH, has been frequently introduced to implement adaptive and adjustable governance tools in water management at a time when scholars have pondered the subject of socio-engineering governance in river flood management. As a result, a good IWRM model may be deemed a suitable governance concept, since it can encompass all of the many parts involved in IWRM. This study evaluated and analyzed effective river flood control cases through collaboration among stakeholders to uncover certain common principles of governance establishment, obtaining the data depicted in Figure 5.

Japan’s SH has been studied concurrently with hydrology and social policy, and it is emerging as an important interdisciplinary research field reflecting the complex relationship between water resources and ongoing social tasks and issues of managing water resources in a rapidly changing social and environmental context. Water-related catastrophes, such as floods, typhoons, and landslides, have long plagued Japan, wreaking havoc on human society and infrastructure. As a result, the Japanese central government has created complex water management technologies, such as levees, dams, and drainage systems, to help reduce the danger of water-related disasters. However, Japanese society is now facing a number of additional water-related concerns, including the consequences of climate change, population growth, and urbanization. These difficulties are exacerbated by social and economic issues, such as land use patterns and demographic shifts, which influence water supply management and distribution.

Japan’s SH aims to address these esoteric issues by combining hydrology, ecology, sociology, and other disciplines to better comprehend the intricate relationships between human civilization and water resources. Thus, researchers in this field are investigating the social and economic effects of floods and other water-related risks, the role of water resources in shaping cultural and historical landscapes, and the development of more sustainable and adaptable water management strategies.

Studies on the impact of the 2011 Great East Japan Earthquake and tsunami on water resources and infrastructure are representative of Japan’s SH study. These studies emphasized Japan’s water resource system’s fragility and the need for a more coordinated and flexible water management strategy [44,45]. Following the catastrophe, SH research looked into how social and economic issues impacted the resilience of water systems, as well as the creation of new disaster planning and response measures. In Japan, flood risk management is seen as a significant concern due to the country’s vulnerability to regular floods [46]. River flooding, typhoon-related urban flooding, and storm surge flooding are all likely in Japan, significantly damaging citizens’ assets/lives, infrastructure, and the economy.

As specified by

Table 5. Coding percentage results with governmental documents via SETS (S1: Social Institution, S2: Communication, S3: Normative/Economy, E1: Ecosystem Conservation, E2: Green Infra., E3: Ecological Service, T1: Technological Design, T2: Engineering Infrastructure, T3: Data Analysis).

SETS Code Category	Social Institution (%)	Communication (%)	Normative/Economy (%)	Ecosystem Conservation (%)	Green Infra. (%)	Ecological Services (%)	Technological Design (%)	Engineering Infra. (%)	Data Analysis (%)
Tokyo	16.9	16.8	5.2	1.9	6.5	7.1	13.9	20.1	11.4
Osaka	10.4	23.2	3.1	0	0.4	16.9	11.6	11.2	23.2
Chiba	31.1	10.2	5.2	3.3	5.2	3.6	10.5	14.8	16.1
Toyama	24.1	27.3	4.8	1.6	2.7	4.3	6.4	13.4	15.5

, local governments in Japan have established comprehensive flood risk management programs that encompass many essential components to proactively prevent and control these losses and dangers [47]. First, to lessen the risk of river flooding, Japanese public institutions have developed a vast network of river management infrastructure, such as dams and embankments. Furthermore, frequent maintenance and monitoring are carried out to ensure that rivers have a clean aquatic ecosystem and flow abundantly. Coastal management is also critical. To lessen the risk of storm surge flooding, Japan’s largest cities have devised a variety of coastal management techniques, including the building of sea walls, breakwaters, and other coastal defense infrastructure. Regular monitoring and assessment of coastal regions is carried out in flood management at the central government level to detect and resolve possible hazards from national catastrophes. For any disaster that occurs on the coast or estuary basin, Japan’s central governmental ministries and local governments have robust disaster preparedness and response systems in place, including early warning systems, evacuation plans, and emergency shelters. To prepare for probable flood occurrences, local communities and key actors in emergency decision-making undergo training and disaster prevention education.

It is critical for disaster management, but its role and significance are difficult to grasp due to structural facility development. Japan’s land use plan enforces severe land use plan laws intended to lower the danger of flooding by limiting growth in flood-prone regions, which causes clashes in goal setting between urban development plans and environmental conservation plans that highlight the goals of development and preservation, respectively.

To flexibly and adaptively manage rainwater runoff produced by concentrated high rains and typhoons, the Japanese government aggressively developed low-impact development (LID) green infrastructure solutions, such as rainwater gardens and green roofs, in each region [48]. To that aim, the importance of community engagement is highlighted, and community members’ participation and contribution, which are also advantages of Japanese culture, are traditionally honored. Against this backdrop, Japanese central ministries and major institutions are collaborating closely with civic communities and governments to develop and share flood risk management strategies, as well as to encourage local residents to participate in disaster preparedness and response efforts in a flexible and calm manner.

Japan’s flood risk management is evolving into a comprehensive and integrated strategy that incorporates physical measures, disaster preparedness and response, land use planning, and community participation to minimize the risk and alleviate the effects of floods. While Japan continues to confront considerable problems in flood risk management, its comprehensive strategy is projected to significantly lessen the impact of floods on the country and its citizens. 

Citizen engagement in flood risk management plays a critical role in catastrophe preparedness and response in Japan. The Japanese government has a long history of involving communities in catastrophe risk reduction, and many of Japan’s flood risk management strategies reflect this type of approach.

5. Conclusions

This paper outlined the socio-hydrology (SH) research framework and highlighted the government-promoted policy direction to comprehensively investigate responses to urban floods in Japanese cities through allomorph analysis. Major hub cities from various regions were chosen to provide a snapshot of regional policies and strategies for dealing with urban floods. The chosen Japanese cities have evolved nuanced approaches to urban flooding that consider their unique histories, topographies, and social cultures. By taking an SH approach, this research work was able to acquire crucial and relevant information that will facilitate future study, including how aspects like the local concerns and climate of each location were incorporated into the strategy.

However, most local governments continue to rely heavily on structural engineering technologies to conduct flood catastrophe mitigation programs. Because cities cannot fully defend themselves against the calamity of urban flooding, this research sought to provide an integrated urban flood control system that considers both engineering and SH viewpoints. SH is a relatively new multidisciplinary field that tries to understand the intricate relationships between civilization and the water resource system, serving as a tool for re-establishing the relationship between floods and cities. Finally, we wanted to deduce the flood control policy implications of Japanese cities using an SH method. The study of the impacts of water resources on people and the effects of people on water is known as SH. This research work looked at nature, society, and politics to understand how people utilize and manage water-related resources in urban society, and we discovered significant changes in the aquatic ecosystem.

Japanese communities have devised many techniques to foster an environment in which residents might engage in flood disaster management. By splitting their different tasks, the central and local governments aimed for cooperative governance. Community-based disaster management is now acknowledged as an essential method of mitigating catastrophe risk. The origins of this societal consensus may be traced back to the Tokugawa shogunate period [49]. This involves citizens of the area taking an active role in the creation of emergency preparation plans, the mapping out of evacuation routes, and the setting up of communication networks. In the case of a catastrophe, citizens who feel a sense of both ownership and duty toward their community are more inclined to act. In everyday life, people should participate in public training and educational programs to achieve this goal.

Local governments in the Toyama and Chiba Prefectures run frequent disaster response public education programs to teach inhabitants about flood hazards and how to prepare for floods. These programs, which aim to promote awareness and educate citizens, contain information on disaster preparedness kits, evacuation procedures, and flood insurance policies. If residents are given access to information, it will be much simpler for them to develop well-informed opinions and take precautions in the case of flood. Citizens also play a part in the government’s monitoring of floods. Citizens of certain communities take it upon themselves to keep an eye on the levels of their local rivers and to alert the appropriate authorities whenever flooding occurs. Because of this, the public and private sectors are able to respond more swiftly and appropriately together to any potential flood problems that may arise. The willingness of individuals in the community to become involved and provide their services is the driving force behind this phenomenon.

Several prefectures, such as the Toyama Prefecture, have developed a solid network of volunteers for disaster relief efforts. Within such networks, residents interact with one another and contribute voluntarily. These volunteers have received training in disaster emergency response, and education and training programs are routinely run to assist with activities such as search and rescue, evacuation, and first aid. Additionally, regular and emergency practice of situational response is conducted twice yearly to better prepare individuals to respond effectively in the event of an emergency. These volunteer networks play the most significant role in aiding local authorities in the case of floods and in responding to the requirements of communities that have been impacted by flooding.

The active engagement of Japanese community members plays a vital role in the implementation of flood risk management strategies in urban areas of Japan. There are many strategies that governments may use to foster the development of resilient and prepared communities in the context of natural disasters like floods. These strategies include actively involving residents at the local level, establishing formal structures for public education and awareness campaigns, and establishing networks of volunteers. Hence, the field of socio-hydrology (SH) in Japan can be succinctly described as a significant and expanding area of study that acknowledges the intricate and interconnected nature of human and natural systems. It advocates for an integrated and sustainable approach to water management, considering the persistent environmental and societal transformations.