Planning Analysis and Simulation
Design Strategies for Floor Plan and Furniture Arrangement to Reduce Flooding Damage in Housing
2025 年 13 巻 3 号 p. 99-116
詳細
2025 年 13 巻 3 号 p. 99-116
In recent years, flood damage in Japan has intensified due to the effects of global climate change. Flood prevention efforts led by public authorities are no longer sufficient to respond to the increasing frequency of flood events. As a result, it is becoming more important for individuals and households to adopt their own protective measures. Meanwhile, Japan’s aging population has led to a growing demand for barrier-free housing designed to support daily mobility. However, such housing often lacks architectural features suited for flood resilience. This study investigates the feasibility of indoor vertical evacuation to the second floor during flood scenarios, particularly when water enters through the entrance. Six barrier-free residential floor plans were analyzed using graph-theoretical indicators, including Total Depth (TD), Mean Depth (MD), Relative Asymmetry (RA), integration (i), Weighted Path Length (WPL), and Flood Critical Value (FCV). Both spatial configuration and furniture placement were evaluated for their impact on evacuation performance. The findings indicate that floor plan layout, staircase position, hallway connectivity, and furniture arrangement all play a critical role in the effectiveness of indoor evacuation. This underscores the importance of evacuation-informed residential design, which integrates architectural planning and interior layout to improve flood resilience at the individual level.
In recent years, flood damage has been increasing in Japan due to global climate change (Aerts, Botzen et al., 2018; Yanagihara, Kazama et al., 2022) .With the growing frequency of floods and the deterioration of flood control infrastructure, flood prevention can no longer rely solely on government interventions (Shrestha, Rasmy et al., 2024). Moreover, in areas with high disaster risk, some residents continue living there due to strong place attachment (Yamashita, Banba et al., 2023) or the presence of social communities (Itma and Khayyat, 2025). Therefore, it has become essential to implement complementary prevention strategies at the individual level. One such measure is to make homes more resilient to flooding (de Andrade, Padilha et al., 2022). This study hypothesizes that optimized floor plan layouts and strategic furniture arrangements can help reduce flood damage and facilitate safer evacuation. For instance, well-considered room configurations may slow the inflow of water, while careful furniture placement can prevent objects from becoming hazardous obstacles during evacuation. In order to think about the specifications of homes that are less susceptible to flooding, such as Japanese society which can reflect the worldwide current state. Japan is aging, and the demand for barrier-free housing by the elderly is increasing (Hirono, 2009, 2022). Furthermore, approximately 80% of elderly people suffer from some form of illness (Liang and Guan, 2023), and it is well known that physical impairments increase the risk of fatalities during disasters due to difficulties in evacuation (Sandoval-Díaz, Navarrete-Valladares et al., 2023). Recognizing these risks, the Japanese government has issued guidelines encouraging residents to prepare for disasters by storing emergency supplies, staying informed, and implementing structural waterproofing (Jusivani, Widana et al., 2024). However, many waterproofing methods such as elevated construction (Reale, 2022), pilotis, or external flood barriers (Nozaka, Satofuka et al., 2015) are not easily compatible with the architectural and functional requirements of barrier-free housing. Additionally, individuals with disabilities often have lower disaster resilience, influenced by factors such as gender, education level, and access to training (Ssennoga, Kisira et al., 2022). Two critical gaps in the existing literature have been identified:
Therefore, this study aims to propose design strategies for floor plans and furniture placement in barrier-free housing to reduce flood-related damage. These strategies are intended to improve evacuation safety, particularly for vulnerable populations such as the elderly and disabled.
Graph theory provides a quantitative framework for the analysis of architectural spaces, serving as a mathematical tool for interpreting spatial configurations. This analytical method originated in 1735, when Euler solved the Königsberg bridge problem by modeling the urban structure as nodes and edges, laying the foundation for graph theory (Wilson, 2003). Graph theory began to influence architectural design and spatial analysis in the 1960s and 1970s. Notably, Alexander (1977) extended graph theory to analyze urban connectivity and inform pattern-based design. In recent decades, it has become a valuable tool for analyzing spatial diagrams and floor planning, offering a structured way to represent spatial relationships (Zhi, Lo et al., 2003). Since the 1980s, Space Syntax has extended graph theory to promote relational and topological thinking in architectural analysis. Central to this approach is the transformation of spatial layouts into topological graphs, enabling analysis through architectural, urban, social, and spatial characteristics (Hanson, 2003; Hillier and Hanson, 1989). Notably, spatial configuration alone has been shown to significantly predict patterns of human movement in both urban contexts and building interiors (Penn, 2003). The Justified Plan Graph (JPG) applies graph-theoretical concepts to hierarchically model building spatial configurations within Space Syntax. Today, it is integrated into various software tools, with expanding applications (Ostwald, 2011). A distinctive feature of the Justified Plan Graph (JPG) method is its emphasis on abstraction based solely on spatial connectivity and sequence. The analysis begins by converting an architectural floor plan into a convex map, which abstracts the space by covering it with the minimum number of maximally extended convex spaces (Hillier and Hanson, 1989). Each convex space is represented as a node, while physical connections between these spaces, such as doors, openings, or corridors, are represented as edges. Collectively, these components constitute a plan graph that captures the compositional connectivity of the building’s interior. Based on the plan graph, various spatial characteristics can be visually interpreted, including:
This method allows spatial structure to be read visually, offering insights into spatial character, patterns of use, and potential social meanings. JPG proves highly valuable by providing a simple, objective, and reproducible framework that enables the interpretation of the same spatial configuration from multiple perspectives. Its flexibility in defining spatial units also facilitates comparative analyses of spatial experiences from different user viewpoints, such as visitors and residents, making it a versatile tool for architectural space analysis (Dovey, 2014; Ostwald, 2011).
This study adopts a qualitative case study approach combined with spatial graph analysis, specifically applying the Justified Plan Graph (JPG) method from space syntax theory, to investigate how floor plan configurations and furniture arrangements affect evacuation during flooding events. Six examples of barrier-free housing in Japan were selected from previous studies and architectural publications. Each case involves elderly or physically disabled residents and features a two-story layout.
The analysis is based on a hypothetical flooding scenario in which water enters the house through the main entrance. It is assumed that residents are located in the living room on the first floor at the time of flooding and must evacuate to the second floor. To ensure consistency, all selected houses meet the following criteria:
Although flooding may occur through windows or back doors, this study simplifies the scenario by focusing exclusively on water ingress through the front entrance. To evaluate evacuation feasibility under such conditions, six residential case studies are analyzed, considering both spatial configuration and furniture arrangement as key factors.
First, the spatial relationships among the entrance, living room, and staircase are examined using the Justified Plan Graph (JPG) method. Each housing layout is modeled as an undirected graph, where rooms and functional spaces are represented as nodes, and physical connections such as doorways and open spaces are represented as edges. The living room is designated as the root node, and the analysis focuses on the evacuation route from the living room to the staircase. Building on Ostwald (2011) approach, this study introduces a Weighted Justified Plan Graph (Weighted JPG) to reflect varying movement difficulties during flooding.
| Connection Type | Weight (w) | Rationale |
|---|---|---|
| Internal connection (no door) | 1.0 | Smooth, unobstructed transition; consistent with Ostwald (2011). |
| Internal connection (with door) | 2.0 | Requires operation; may be obstructed during flooding. |
| Outdoor passage | 4.0 | Significantly impairs movement due to flooding risk and reduced walking speed. |
These weight values are informed by empirical findings reported by Dias, Abd Rahman et al. (2021), which indicate that walking speed decreases by approximately 50% in water depths greater than 0.5 meters and that outdoor movement imposes substantially greater physical and temporal demands compared to indoor movement. Based on these considerations, we assign a maximum edge cost of 4.0 to outdoor paths to reflect their relative burden. Using this weighted model, the following graph-theoretical metrics are calculated to evaluate the suitability of evacuation routes.
| Abbr. | Full Term | Definition / Explanation |
| TD | Total Depth | The total weighted distance from the root node to all other nodes in the graph. |
| MD | Mean Depth | The average number of steps from the selected space to all other spaces |
| RA | Relative Asymmetry | An index reflecting spatial depth and structural asymmetry. |
| i | integration | A measure of how central or accessible a space is within the overall configuration. |
| WPL | Weighted Path Length | The total cost of the shortest paths between nodes, based on edge weights such as doors and outdoor connections. |
| FCV | Flood-aware Control Value | A modified control value that incorporates edge weights to reflect movement difficulty under flood conditions. |
This weighted approach enables a more nuanced analysis of spatial accessibility, taking into account both the physical layout and the expected difficulty of movement during flood scenarios. It allows for direct comparison of the efficiency and resilience of evacuation routes across different housing layouts, especially the critical path from the living room (L) to the staircase (S).
In parallel, the analysis also evaluates the role of furniture placement in shaping evacuation feasibility. The types, dimensions, and placements of furniture in the living room are assessed to determine their potential to obstruct evacuation routes or become hazardous during flooding. Emphasis is placed on circulation width, furniture density, and the presence of movable objects that may shift due to water pressure.
In this section, we analyze six case studies focusing on floor plan configurations and furniture arrangements. Table 3 presents the key characteristics of each case. The cases were selected based on four criteria, drawn from Jutaku Tokushu and previous academic research: (1) labeled as “barrier-free” or “two-generation” housing; (2) availability of detailed floor plans and household data; (3) occupied by elderly or physically disabled residents; and (4) designed as two-story homes.
| First Floor Layout | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Room | Corridor | |||||||||||
| Total Floor area (m2) | Floor Level | Family Type | L+D+K | LD+K | L+DK | LDK | Western-style | Japanese-style room | be | none | ||
| 1 | unknown | 2Floor | Single-person | ◯ | 1 | 1 | ◯ | |||||
| 2 | 153.59 | 3Floor | Couple | ◯ | 2 | - | ◯ | |||||
| 3 | 125.07 | 2Floor | Couple | ◯ | 1 | 1 | ◯ | |||||
| 4 | 201.44 | 2Floor | Duplex | Child | ◯ | - | - | ◯ | ||||
| Parent | ◯ | - | - | ◯ | ||||||||
| 4 | 202.03 | 2Floor | Duplex | Child | Child | ◯ | - | - | ◯ | |||
| Parent | Parent | ◯ | - | - | ◯ | |||||||
| 6 | 166.14 | 1Floor | Couple | ◯ | 2 | - | ◯ | |||||
As shown in Figure 1, Case 1 is occupied by elderly residents. The entrance and living room are diagonally positioned, and the staircase is located near the center of the house. Furniture in the living room creates a narrow passage, and evacuation requires passing through the dining kitchen and hallway against the direction of floodwater, increasing both complexity and risk.
As shown in Figure 2, Case 2 involves a couple who use wheelchairs. The living room is located immediately after the entrance. The furniture includes a central table and a storage shelf that functions as a room divider. In the event of evacuation to the second floor, residents must first exit the house and go outside to access the staircase. As shown in Figure 3, the third case is a barrier-free house occupied by a couple and their two children. The hallway and rooms are arranged in a circular configuration, allowing smooth circulation. Furniture is rarely placed in passage areas, and most pieces are fixed in place. There are two available routes for residents to evacuate from the living room to the second floor.
As shown in Figure 3, Case 3 is a barrier-free house occupied by a couple and their two children. The hallway and rooms are configured in a circular layout, allowing for uninterrupted movement throughout the house. Furniture is rarely placed in passage areas, and most items are securely fixed in place to prevent displacement. There are two possible routes for residents to evacuate from the living room to the second floor, offering flexibility during emergencies.
As shown in Figure 4, Case 4 is a two-family home. In both households, the living room is located immediately beyond the front entrance, with a central table as the primary furniture arrangement. The children's household has a storage shelf placed near the entrance, while the parents' household places theirs in a recessed area. During evacuation, residents from both households use staircases located adjacent to their respective living rooms to access the second floor.
As shown in Figure 5, Case 5 is a two-family home with the entrances to the parent and child households positioned diagonally opposite each other. In the parent household, residents must pass through a courtyard to reach the living room. While the child household places storage furniture along the wall, the parent household utilizes a dedicated storage room. During evacuation, the lack of an internal staircase in the parent household requires residents to traverse the courtyard, enter the child household’s home, and then go up the stairs. This results in a significant detour.
As shown in Figure 6, Case 6 is a barrier-free house occupied by a couple. A hallway extends from the entrance to the centrally positioned living room. No furniture is placed along the evacuation route, and a dedicated storage room is provided separately. In the event of flooding, residents can evacuate to the second floor via a staircase located directly within the living room, enabling a quick and unobstructed escape.
This study conducted a comprehensive evaluation of evacuation routes from the living room to the staircase under flood conditions, using graph theory and spatial configuration analysis. Six evaluation indicators were applied: Total Distance (TD), Maximum Depth (MD), Relative Asymmetry (RA), Inclination (i), Weighted Path Length (WPL), and Flood Critical Value (FCV). The analysis results for Case 1 through Case 3 are summarized in Figure 7 and those for Case 4 through Case 6 are presented in Figure 8.
The shortest TD values were observed in CASE2 (18,000) and CASE6 (22,000), and in both cases, shorter travel distances tended to correspond with favorable values for FCV and WPL. In contrast, CASE4 exhibited an extremely long TD (62,000), and CASE1 also recorded a relatively high value (40,000), suggesting that circuitous layouts and a high degree of spatial circulation impose a significant burden on evacuees.
CASE2 (2.571) and CASE6 (2.444) exhibited low MD values, which correlated with relatively low FCV scores and suggested a higher likelihood of safe evacuation. . In contrast, CASE1 (5.000), CASE4 (5.167), and CASE5 (4.700) recorded significantly higher MD values, identifying them as routes associated with greater flood-related risk.
The lowest RA values were observed in CASE6 (0.361) and CASE2 (0.524), both of which were strongly associated with greater evacuation ease. In contrast, CASE1 (1.143) had the highest RA, indicating a more isolated and less accessible configuration. This implies that even if WPL or FCV values are favorable, high RA may hinder access and increase overall evacuation difficulty.
While Case 2 (i = 1.909) and Case 6 (i = 2.769) performed well in other indicators such as TD, FCV, and WPL, their relatively high i values suggest that evacuation may still require considerable physical effort, posing potential challenges for vulnerable residents. In contrast, Case 4 exhibited a lower i value (1.320), indicating fewer immediate obstacles; however, this advantage was offset by its long total travel distance (TD = 62,000) and high structural asymmetry (RA), both of which continued to hinder effective evacuation.
Furthermore, in cases like Case 4, where multiple evacuation destinations exist, different values for i, TD, and other indicators may be produced depending on the route taken. This highlights the importance of predefining evacuation routes in advance to minimize confusion and ensure the most efficient and accessible path is used during an emergency.
Extremely low WPL values were observed in Case 6 (1.0) and Case 4a (1.0), reflecting highly efficient movement paths. Although Case 2 exhibited a moderate WPL, it achieved excellent scores in RA and FCV, suggesting a well-balanced and overall effective evacuation configuration.
Routes such as CASE2_ROUTE1 (4.583), CASE4a (3.708), and CASE6 (5.500) showed low FCV scores and were evaluated as safer evacuation options. In contrast, CASE4b exhibited a significantly higher FCV (9.125), along with degraded WPL and TD values, demonstrating that even within the same home, different evacuation destinations can result in vastly different risk profiles. CASE5 recorded the highest FCV (11.125) and performed poorly across all other indicators, identifying it as the least suitable evacuation route.
Floor plan AnalysisEvacuation feasibility in residential settings is shaped by spatial connectivity and the complexity of circulation. This study focuses on three key aspects: the complexity of evacuation routes, the positioning of hallways, and the location of staircases as evacuation destinations. These factors directly influence evacuation clarity, efficiency, and safety during flooding and are essential to residential design.
a. Evacuation route complexity
The configuration of a residential floor plan directly influences the simplicity of evacuation paths and the likelihood of blockage during emergencies. In many homes, priority is placed on providing direct access from the entrance to the living room. However, incorporating a corridor between these spaces can compartmentalize interior zones and slow the intrusion of floodwater. In CASE1 and CASE5, residents must pass through multiple rooms and doors to reach the staircase from the living room. This results in a high number of transition steps and creates complex evacuation routes. In such configurations, the potential for evacuation blockage increases significantly if doors become damaged or inoperable, contributing to elevated Weighted Path Length (WPL) and Flood Critical Value (FCV) scores. In contrast, CASE4 and CASE6 feature staircases located directly within the living room, thereby minimizing the number of rooms that must be traversed. This spatial simplicity facilitates rapid and straightforward evacuation. Moreover, because residents do not need to move toward the entrance, which is often the source of flooding, these layouts inherently enhance evacuation safety. Accordingly, both cases demonstrated favorable values for WPL and Relative Asymmetry (RA).
b. Spatial connectivity through hallway
The location of the hallway, rather than its mere presence, plays a crucial role in determining the clarity and efficiency of movement within a home. When the hallway is centrally located and connects all major spaces, movement lines become more organized, and spatial transitions are clearly defined. This configuration typically results in lower Relative Asymmetry (RA) values, indicating better spatial accessibility and supporting more effective evacuation. A centrally connected hallway also allows occupants from multiple rooms to access a shared evacuation path, increasing route flexibility and contributing to lower Flood Critical Value (FCV) scores. In contrast, when the hallway is not centrally located or does not exist, residents are often required to pass through other rooms to reach exits. This leads to complex, indirect circulation routes, resulting in higher RA and limited evacuation options, which in turn negatively impact both WPL and FCV.
c. Staircase Position and Evacuation Directionality
The analysis of CASE4 and CASE6 provides important insights into the relationship between staircase positioning and evacuation feasibility. In both cases, the staircases are located within the living room, allowing for a direct vertical evacuation route from the primary living space. This configuration minimizes the number of transitional spaces, shortens Total Distance (TD) and Weighted Path Length (WPL), and eliminates the need to move toward the entrance, which is typically the floodwater entry point. As a result, evacuation can be executed more quickly and with greater safety. Based on these findings, it can be concluded that in scenarios where evacuation to a second floor is necessary, the position of the staircase becomes a critical factor. In many conventional homes, staircases are situated near the entrance, which is often aligned with the direction of floodwater intrusion. This layout forces residents to move against the incoming water flow, significantly increasing evacuation risk. By contrast, when staircases are placed adjacent to the living room and oriented away from the flood source, vertical evacuation becomes both safer and more efficient.
The comparative analysis of six residential case studies using graph-theoretical evacuation indicators revealed that evacuation feasibility is a complex, multidimensional issue. It cannot be adequately assessed through a single metric, but rather requires the integrated evaluation of multiple spatial and risk-related factors. Among the indicators examined, Relative Asymmetry (RA), which reflects spatial depth and structural asymmetry, and Flood Critical Value (FCV), which indicates flood-related vulnerability, were identified as the most influential factors in determining evacuation difficulty. These indicators should be prioritized in architectural design to improve evacuation performance in residential environments. CASE2 and CASE6 demonstrated spatial configurations that were well balanced, with low RA, low FCV, and short Weighted Path Length (WPL), making them effective examples of evacuation-oriented housing. However, the relatively high i value observed in CASE2 indicates that physical effort may remain a concern. This is likely due to the external location of the staircase, which requires residents to exit the primary living area during evacuation. CASE4 further illustrated the complexity of evacuation planning, as evacuation performance differed significantly depending on whether the destination was Sa or Sb. This outcome highlights the need to consider not only the evacuation route itself but also the final destination in order to develop a fully optimized evacuation strategy. Overall, the findings indicate that effective evacuation design requires a comprehensive approach that incorporates spatial layout, the clarity of circulation, furniture arrangement, and the location of the evacuation endpoint. The application of graph-theoretical indicators offers a practical and reliable framework for assessing and enhancing disaster resilience in housing environments.
Furniture AnalysisIn this section, we present a comparative analysis of furniture arrangements across six residential case studies. Particular attention is given to the placement of furniture in living and dining areas, where residents typically spend most of their time, and to how these arrangements may affect evacuation routes.
| Furniture Name | Impact | Observations | |
|---|---|---|---|
| Dining | Dining table | ◯ | Because it is larger than the width of the door, it blocks passage through the door. If it falls over, evacuees may be injured by the collision, making evacuation difficult. |
| Dining chair | ◯ | If the vehicle falls over, evacuees may be injured by the collision, making evacuation difficult. | |
| Cupboard (entrance side) | ◯ | If the shelf moves, it will prevent the door from opening and closing, blocking the evacuation route. Also, if the shelf falls over, evacuees may be injured and it will be difficult to evacuate. | |
| Cupboard (kitchen side) | × | As long as there is no collision or interference with other furniture, even if the shelf moves or tips over, it will not directly affect evacuation routes. | |
| Living | Sofa | ◯ | It is larger than the width of the door, so it blocks passage through the door. Its weight makes it difficult to evacuate if evacuees are injured by collisions or being crushed by furniture. |
| Low table | ◯ | If an evacuation route is blocked, evacuees who are unable to lift their feet will have difficulty escaping. | |
| Chair | × | The height and shape of the furniture are such that even if it is on an evacuation route, it will not completely block the passageway. | |
| Fan | × | The height and shape of the furniture are such that even if it is on an evacuation route, it will not completely block the passageway. | |
| TV set | × | Even if it falls over, it will not block evacuation routes. | |
| Boombox | × | Even if it falls over, it will not block evacuation routes. | |
| Massage chair | × | Since it is located in the corner of the room, it has little impact on evacuation routes. |
| Furniture Name | Impact | Observations | |
|---|---|---|---|
| Dining | Dining table | ◯ | It is located in the center of the evacuation route and therefore poses an obstacle to evacuation. |
| Living | Dining chair | × | Because it is located in the center of the evacuation route, it will hinder evacuation. Also, if furniture falls over and injures evacuees, |
| TV stand | ◯ | Since the longest length of the furniture is equal to the width of the passageway in the evacuation route, if the furniture rotates, the evacuation route will be blocked. | |
| Storage rack(Fixation) | × | They are located parallel to the passageway, ensuring an evacuation route. |
| Furniture Name | Impact | Observations | |
|---|---|---|---|
| Living | Sofa(Fixation) | × | It is not on an evacuation route and will not move, so it will have little impact on evacuation. |
| Table | × | It is not on an evacuation route and will not move, so it will have little impact on evacuation. | |
| TV set | × | A falling television could injure nearby evacuees, but it is not on the evacuation route. | |
| TV stand(Fixation) | × | It is not on an evacuation route and will not move, so it will have little impact on evacuation. | |
| Kitchen | Dining table | × | It is located in a corner and is not on an evacuation route, so it has little impact on evacuation. |
| Dining | Dining chair | × | It is located in a corner and is not on an evacuation route, so it has little impact on evacuation. |
| Storage shelf (fixed) | × | They are placed in corners and do not move, so they have little impact on evacuation. |
| Furniture Name | Impact | Observations | ||
|---|---|---|---|---|
| Child household | Dining | Dining table | ◯ | Because it is located in the center of an evacuation route, the furniture could move or tip over and hinder evacuation. |
| Living | Dining chair | ◯ | Because it is located in the center of an evacuation route, the furniture could move or tip over and hinder evacuation. | |
| TV stand | × | It is not located on an evacuation route, and even if it is rotated, it has little effect on evacuation because the width of the furniture is smaller than the evacuation route passage. | ||
| TV set | × | It is not located on an evacuation route, and even if it is rotated, it has little effect on evacuation because the width of the furniture is smaller than the evacuation route passage. | ||
| Storage rack | ◯ | They are placed near the entrances and exits of evacuation routes, and may interfere with the opening and closing of doors or block evacuation routes if they move. | ||
| Parent household | Dining | Dining table | ◯ | Because it is located in the center of an evacuation route, the furniture could move or tip over and hinder evacuation. |
| Living | Dining chair | ◯ | Because it is located in the center of an evacuation route, the furniture could move or tip over and hinder evacuation. | |
| TV stand | × | As it is not on an evacuation route and is located secluded, it has little effect on evacuation. | ||
| TV set | × | As it is not on an evacuation route and is located secluded, it has little effect on evacuation. | ||
| Storage rack(Horizontal) | ◯ | They are placed near the entrances and exits of evacuation routes, and may interfere with the opening and closing of doors or block evacuation routes if they move. | ||
| Storage rack(Vertical) | × | As it is not on an evacuation route and is located secluded, it has little effect on evacuation. | ||
| Cupboard(Fixation) | × | Since the shelves are fixed on the evacuation route, they do not move and have little effect on evacuation. |
| Furniture Name | Impact | Observations | ||
|---|---|---|---|---|
| Child household | Kitchen | Dining table | ◯ | It is located on the evacuation route for the parent household, and if the furniture moves or falls over, it could hinder evacuation. |
| Dining | Dining chair | ◯ | It is located on the evacuation route for the parent household, and if the furniture moves or falls over, it could hinder evacuation. | |
| Living | TV stand | ◯ | They are placed near the entrances and exits of evacuation routes, and may interfere with the opening and closing of doors or block evacuation routes if they move. | |
| TV set | ◯ | They are placed near the entrances and exits of evacuation routes, and may interfere with the opening and closing of doors or block evacuation routes if they move. | ||
| Storage rack | × | As it is not on an evacuation route and is located secluded, it has little effect on evacuation. | ||
| Parent household | Living | not clear | - | - |
| Furniture Name | Impact | Observations | |
|---|---|---|---|
| Dining | Fireplace | × | Because it is fixed in place, it has little effect on evacuation. |
| Living | Dining table | × | It is located in a corner and is not on an evacuation route, so it has little impact on evacuation. |
| Dining chair | × | It is located in a corner and is not on an evacuation route, so it has little impact on evacuation. |
While furniture such as dining tables, chairs, and storage shelves serves essential daily functions, it can become a major obstacle during emergency evacuations. This is particularly true in narrow hallways or common living spaces where large furniture items are present. In such cases, collapsed or overturned furniture can block evacuation pathways, potentially increasing the actual Weighted Path Length (WPL) and delaying safe egress. Furthermore, in many homes, storage shelves are placed near architectural features such as doors or windows, where their collapse during earthquakes or flooding poses a high risk of blocking exit points entirely. This type of obstruction presents a critical hazard and should be considered a qualitative factor in the assessment of the Flood Critical Value (FCV).
Across all six case studies, dining tables and chairs were placed in the living room. When these furnishings were positioned at the center of the space, as seen in Case 1 through Case 5, they directly interfered with the flow of evacuation, particularly in floor plans where the evacuation route passes through the living room. In such configurations, furniture placement contributes structurally to increased Weighted Path Length (WPL) and elevated Flood Critical Value (FCV), due to blocked or delayed movement during emergencies. In contrast, Case 4 and Case 6 featured more effective furniture arrangements. In these cases, some furniture was installed within recessed wall areas, which helped to maintain clear evacuation paths. This type of layout, which avoids circulation routes, reduces the likelihood of obstruction caused by displaced or fallen objects and serves as a practical strategy for evacuation-conscious interior design. Additionally, many homes had storage shelves placed near doorways, which increases the risk of evacuation routes being blocked if these items fall during a flood. Even when the WPL appears short in plan view, actual evacuation feasibility may be significantly reduced in such cases, leading to a higher effective FCV. For this reason, furniture positioning should be considered a complementary qualitative factor in evacuation evaluations and should be incorporated into both the design phase and post-occupancy safety assessments.
This study assessed the feasibility of second-floor evacuation during flooding, with a specific focus on water entering through the main entrance. The analysis was based on six barrier-free residential case studies and utilized graph-theoretical indicators to evaluate spatial characteristics. The results demonstrated that evacuation performance is not determined by any single factor but rather by the combined influence of spatial layout, circulation flow, and furniture arrangement. The following design considerations were identified as particularly important.
・Efficient vertical evacuation is facilitated when staircases are located adjacent to the living room, ideally positioned in the opposite direction of the flood source (typically the entrance).
・Centrally located hallways improve access to evacuation routes, lower spatial asymmetry (RA), and enhance evacuation efficiency.
・Avoiding furniture placement along movement lines and ensuring that heavy items are secured and kept away from exits reduces obstruction risk and contributes to overall evacuation safety.
Among the six cases, CASE6 demonstrated an optimal configuration with low RA, low FCV, and short WPL. In contrast, CASE4 showed that evacuation feasibility can vary significantly depending on the destination point (Sa or Sb), emphasizing the need to consider not only the route but also the endpoint in evacuation planning. The findings affirm that evacuation feasibility is a multidimensional issue, with RA and FCV emerging as particularly influential indicators. A combined evaluation of efficiency (TD, WPL) and safety (MD, FCV) provides a more realistic basis for evacuation-focused residential design.
Based on these findings, two key directions are suggested for future research. The first is to conduct post-disaster case studies of homes that have experienced flooding, in order to examine the relationship between flood damage and spatial or furniture configurations using the framework developed in this study. The second is to apply flood simulation models to quantitatively evaluate the effectiveness of evacuation-oriented design strategies under various flooding conditions. These perspectives reinforce the conclusion that architectural planning should explicitly incorporate emergency scenarios, and that the integration of spatial analysis with graph-based modeling provides a practical foundation for enhancing residential flood resilience.
Conceptualization, S.C. and H.G.; methodology, S.C. and H.G.; software, S.C.; investigation, S.C.; resources, H.G.; data curation, S.C.; writing—original draft preparation, S.C.; writing—review and editing, S.C., H.G. and L.G.; supervision, H.G.; project administration, H.G.; validation and feedback, L.G..
The authors declare that they have no conflicts of interest regarding the publication of the paper.
The authors would like to express their sincere gratitude to Prof. Huang Guangwei for his continuous guidance and valuable suggestions throughout the study. The authors also thank Lin Gang for his constructive feedback and help in refining the manuscript.
