Blue-Green Infrastructure for Flood and Water Quality Management in Southeast Asia: Evidence and Knowledge Gaps

Laboratory performance assessment of low-cost water level sensor for field monitoring in the tropics

As Water Sensitive Urban Design (WSUD) is a key strategy in integrated urban water management worldwide, there is a need for robust monitoring of WSUD systems. Being economical and flexible for operation and communication, low-cost sensor systems show great potential to mainstream digital water management. Yet, such systems are insufficiently tested, casting doubt on the reliability of their measurements. Here, we document a robust testing approach for a pressure transducer water level low-cost sensor (KIT0139) and a traditional sensor (OTT PLS) in both laboratory and field conditions. We tested six different devices under three temperatures relevant to tropical climate: 25, 30, 35 °C and proposed a field calibration approach. Results reveal that the low-cost sensors were robust as the six individual devices performed consistently under different testing conditions. After calibration, low-cost sensors provided sufficient accuracy (±10mm) and precision for water levels more than 0.05m. While varying water flow direction did not significantly influence the performance, we showed that calibration should be done for individual devices. In addition, large (>5 °C) variations in water temperature and varying wet/dry conditions may also influence the performance of the low-cost sensors. The field calibration approach was validated in a 3-month experiment, confirming that this model of low-cost sensor can effectively replace traditional sensors in the field in tropical climates. Our study confirms that systematic and thorough testing is needed for low-cost sensors systems to realize their full potential for scientific-grade applications. We provide practical recommendations to conduct such testing from the laboratory to the field.

Contextualising potential zones for ecosystem-based adaptation in Lower Northern Thailand: A mixed method analysis for water resources management

Ecosystem-based adaptation (EbA) has been accepted widely in integrating climate adaptation with water resources management, yet the pilot study of this issue is understudied in small urban areas of Thailand. This research addresses climate induced variability affecting water-related disasters and ecosystem degradation, as well as analyses potential zones in supporting EbA initiatives by the blue-green infrastructures (BGIs) in Si Samrong District located at the Yom River basin's floodplain, Lower Northern Thailand. Using a mixed method analysis in portraying the possibility of EbA, correlation analysis is applied to illustrate relationships among rainfall, temperature, and runoff from both on-ground statistical and climate modelling information under climate variability. Questionnaire survey with 405 respondents and focus group discussions with 68 local representatives in seven sub-districts were conducted quantitatively and qualitatively to understand water and environmental-related conditions affecting livelihoods and local demands for EbA initiatives. Overlay analysis by GIS and field survey are also adopted to analyse potential areas for EbA based on main and supporting factors in physical and socio-economic dimensions for initiating five BGIs. Then, suitable areas were classified and grouped as potential zones. Results indicate that climate variability exists in both scientific evidence and local perceptions; however, they perceive this variability through uncertainties on water resources, agriculture, daily living, health impacts, and the ecosystem. This circumstance requires tailor-made selection and implementation of BGIs for promoting water equilibrium, rehabilitating ecosystem, and building resilience for livelihoods based on urban complexities in a small town. In this regard, five potential zones are created with different conditions in achieving EbA initiatives.

Construction and optimization of Green Infrastructure Network in mountainous cities: a case study of Fuzhou, China

Green infrastructure networks enhance the protection and improvement of urban ecological environments, augment the efficiency and quality of ecosystem services, and furnish residents with healthier and more comfortable living conditions. Although previous research has investigated the construction or optimization methods of green infrastructure networks, these studies have been relatively isolated and lacking in case studies for mountainous cities. In the development of green infrastructure, mountainous cities must specifically consider the impact of terrain on network construction. Taking Fuzhou, a mountainous city in China, as an example, this study constructs and optimizes the green infrastructure network by employing morphological spatial pattern analysis, connectivity analysis, the Minimum Cumulative Resistance model, and circuit theory. These methodologies increase the connectivity of the Green Infrastructure within the study area, thereby promoting the health of the local ecosystem and creating conducive circumstances for the city's sustainable development. The findings reveal that: (1) Green infrastructure in Fuzhou takes up 5366.38 ha, constituting 21.76% of the study area, primarily situated in the northwest and south; (2) Fuzhou's Green Infrastructure network comprises 10 hubs and 17 corridors with a hub area of 1306.98 ha, predominantly distributed in the mountains encircling the city, including Meifeng Mountain, Gaogai Mountain, and Qingliang Mountain; (3) Based on optimization, the circuit centrality index categorizes hub importance into three protection levels, pinpointing nine crucial protected areas in the corridors and 680 areas requiring enhancement, including 68 areas for first-level improvement, 149 areas for second-level improvement, and 463 areas for third-level improvement. This research offers a methodological reference for constructing and optimizing green infrastructure networks in mountainous cities, providing both theoretical and practical foundations for optimizing green infrastructure networks in Fuzhou City.

A systematic review on urban blue-green infrastructure in the south Asian region: recent advancements, applications, and challenges

This study uses a Systematic Literature Review (SLR) process to know the present status of research on urban Blue-Green Infrastructure (BGI) in the lower-middle-income countries of the South Asian region, specifically India, Bangladesh, Sri Lanka, Bhutan, Nepal, and Pakistan, which produced 77 relevant publications after detailed scanning published between 2013 and 2022. It was aimed to analyze variations on BGI's mentions in different regions, identify BGI components found in the literature and their uses to promote urban sustainability, research initiatives, and priorities, and identify knowledge gaps for future research. The review reveals significant differences in research distribution among countries, with the majority of the articles focusing on green spaces compared to bluescapes and concentrating on topics like local inhabitant's perception of urban green spaces, advantages of implementing nature-based solutions, the role of green infrastructures in minimizing the urban heat island effect, air pollution, etc. Articles highlighted the lack of governance and the challenges in implementing and designing a BGI network. However, articles discussing a holistic methodology to implement BGI for promoting urban sustainability were limited. Gaps still exist in determining the appropriate strategy for the scope identification, creation, management, and governance of BGI and integrating it with existing grey infrastructure.

Low-cost monitoring systems for urban water management: Lessons from the field

Sound urban water management relies on extensive and reliable monitoring of water infrastructure. As low-cost sensors and networks have become increasingly available for environmental monitoring, urban water researchers and practitioners must consider the benefits and disadvantages of such technologies. In this perspective paper, we highlight six technical and socio-technological considerations for low-cost monitoring technology to reach its full potential in the field of urban water management, including: technical barriers to implementation, complementarity with traditional sensing technologies, low-cost sensor reliability, added value of produced information, opportunities to democratize data collection, and economic and environmental costs of the technology. For each consideration, we present recent experiences from our own work and broader literature and identify future research needs to address current challenges. Our experience supports the strong potential of low-cost monitoring technology, in particular that it promotes extensive and innovative monitoring of urban water infrastructure. Future efforts should focus on more systematic documenting of experiences to lower barriers to designing, implementing, and testing of low-cost sensor networks, and on assessing the economic, social, and environmental costs and benefits of low-cost sensor deployments.

Urban Trees and Hydrological Ecosystem Service: A Novel Approach to Analyzing the Relationship Between Landscape Structure and Runoff Reduction

Urban stormwater runoff has posed significant challenges in the face of urbanization and climate change, emphasizing the importance of trees in providing runoff reduction ecosystem services (RRES). However, the sustainability of RRES can be disturbed by urban landscape modification. Understanding the impact of landscape structure on RRES is crucial to manage urban landscapes effectively to sustain supply of RRES. So, this study developed a new approach that analyzes the relationship between the landscape structural pattern and the RRES in Tabriz, Iran. The provision of RRES was estimated using the i-Tree Eco model. Landscape structure-related metrics of land use and cover (LULC) were derived using FRAGSTATS to quantify the landscape structure. Stepwise regression analysis was used to assess the relationship between landscape structure metrics and the provision of RRES. The results indicated that throughout the city, the trees prevented 196854.15 m3 of runoff annually. Regression models (p ≤ 0.05) suggested that the provision of RRES could be predicted using the measures of the related circumscribing circle metric (0.889 ≤ r2 ≤ 0.954) and the shape index (r2 = 0.983) of LULC patches. The findings also revealed that the regularity or regularity of the given LULC patches' shape could impact the patches' functions, which, in turn, affects the provision of RRES. The landscape metrics can serve as proxies to predict the capacity of trees for potential RRES using the obtained regression models. This helps to allocate suitable LULC through optimizing landscape metrics and management guidance to sustain RRES.

Evaluating urban green and blue spaces with space-based multi-sensor datasets for sustainable development

Urban green and blue spaces refer to the natural and semi-natural areas within a city or urban area. These spaces can include parks, gardens, rivers, lakes, and other bodies of water. They play a vital role in the sustainability of cities by providing a range of ecosystem services such as air purification, carbon sequestration, water management, and biodiversity conservation. They also provide recreational and social benefits, such as promoting physical activity, mental well-being, and community cohesion. Urban green and blue spaces can also act as buffers against the negative impacts of urbanization, such as reducing the heat island effect and mitigating the effects of stormwater runoff. Therefore, it is important to maintain and enhance these spaces to ensure a healthy and sustainable urban environment. Assessing urban green and blue spaces with space-based multi-sensor datasets can be a valuable tool for sustainable development. These datasets can provide information on the location, size, and condition of green and blue spaces in urban areas, which can be used to inform decisions about land use, conservation, and urban planning. Space-based sensors, such as satellites, can provide high-resolution data that can be used to map and monitor changes in these spaces over time. Additionally, multi-sensor datasets can be used to gather information on a variety of environmental factors, such as air and water quality, that can impact the health and well-being of urban residents. This information can be used to develop sustainable solutions for preserving and enhancing urban green and blue spaces. This study examines how urban green and blue infrastructures might improve sustainable development. Space-based multi-sensor datasets are used to estimate urban green and blue zones for sustainable development. This work can inform sustainable development research at additional spatial and temporal scales.

Nature-based solutions to enhance urban flood resiliency: case study of a Thailand Smart District

A Research through Designing approach was used to explore nature-based solutions (NbS) for flood management at the fluvial (regional) and pluvial (local) scales as part of a Smart District visioning study in a peri-urban area north of Bangkok, Thailand. The NbS visions were informed by community surveys (total n = 770) as well as in-depth, semi-structured interviews with community leaders and key stakeholders representing private sector business. Both fluvial and pluvial flooding commonly occur in the study area and the cost of damage incurred by individuals generally exceeds aid remuneration. The surveys revealed that flood insurance was not widely used as a form of resiliency to flood conditions. Furthermore, survey participants generally considered common space and green space unsatisfactory and inadequate to meet community needs. In light of these survey responses, example NbS visions were developed to address community concerns and promote well-being, while concurrently providing resiliency and improved ecosystem services through connectivity of blue and greenscapes. This case study provides a novel linkage between the concepts of NbS, Research through Designing, and Smart City/District, in exploring sustainable and resilient approaches to flood management in the context of tropical, Global South development and also provides a first step towards developing an NbS typology.

Spatio-temporal development of the urban heat island in a socioeconomically diverse tropical city

Urban heat islands, where temperatures are elevated relative to non-urban surrounds, are near-ubiquitous in cities globally. Yet, the magnitude and form of urban heat islands in the tropics, where heat has a large morbidity and mortality burden, is not well understood, especially for those of urban informal settlements. We used 29 years of Landsat satellite-derived surface temperature, corroborated by in situ temperature measurements, to provide a detailed spatial and temporal assessment of urban heat islands in Makassar, Indonesia, a city that is representative of rapidly growing urban settlements across the tropics. Our analysis identified surface urban heat islands of up to 9.2 °C in long-urbanised parts of the city and 6.3 °C in informal settlements, the seasonal patterns of which were driven by change in non-urban areas rather than in urban areas themselves. In recently urbanised areas, the majority of urban heat island increase occurred before land became 50% urbanised, whereas the established heat island in long-urbanised areas remained stable in response to urban expansion. Green and blue space protected some informal settlements from the worst urban heat islands observed across the city and maintenance of such space will be essential to mitigate the growing heat burden from urban expansion and anthropogenic climate change. Settlements further than 4 km from the coast and with Normalised Difference Vegetation Index (NDVI) less than 0.2 had higher surface temperatures, with modelled effects of more than 5 °C. Surface temperature measurements were representative of in situ heat exposure, measured in a subset of 12 informal settlements, where mean indoor temperature had the strongest relationship with surface temperature (R² = 0.413, P = 0.001). We advocate for green space to be prioritised in urban planning, redevelopment and informal settlement upgrading programs, with consideration of the unique environmental and socioeconomic context of tropical cities.

Incorporating Microbial Species Interaction in Management of Freshwater Toxic Cyanobacteria: A Systems Science Challenge

Water resources are critically important, but also pose risks of exposure to toxic and pathogenic microbes. Increasingly, a concern is toxic cyanobacteria, which have been linked to the death and disease of humans, domesticated animals, and wildlife in freshwater systems worldwide. Management approaches successful at reducing cyanobacterial abundance and toxin production have tended to be short-term solutions applied on small scales (e.g., algaecide application) or solutions that entail difficult multifaceted investments (e.g., modification of landscape and land use to reduce nutrient inputs). However, implementation of these approaches can be undermined by microbial species interactions that (a) provide toxic cyanobacteria with protection against the method of control or (b) permit toxic cyanobacteria to be replaced by other significant microbial threats. Understanding these interactions is necessary to avoid such scenarios and can provide a framework for novel strategies to enhance freshwater resource management via systems science (e.g., pairing existing physical and chemical approaches against cyanobacteria with ecological strategies such as manipulation of natural enemies, targeting of facilitators, and reduction of benthic occupancy and recruitment). Here, we review pertinent examples of the interactions and highlight potential applications of what is known.

Spatial Planning and Systems Thinking Tools for Climate Risk Reduction: A Case Study of the Andaman Coast, Thailand

The impact of climate change and related hazards such as floods, heatwaves, and sea level rise on human lives, cities, and their hinterlands depends not only on the nature of the hazard, but also on urban development, adaptation, and other socioeconomic processes that determine vulnerability and exposure. Spatial planning can reduce climate risk not just by influencing the exposure, but also by addressing social vulnerability. This requires that relevant information is available to planners and that plans are implemented and coordinated between sectors. This article is based on a research project in Thailand, particularly on the results of multi-sectoral workshops in the case study region of the Andaman Coast in southern Thailand, and draws upon climate risk, spatial planning, and systems thinking discourses. The article formulates recommendations for planning in the context of Thailand that are relevant for other rapidly growing and urbanizing regions. Among other conclusions, it suggests that systems thinking approaches and cross-sectoral strategies are ways to grasp the interdependencies between and within climate risk and spatial development challenges.

Influence of Low-Impact Development in Flood Control: A Case Study of the Febres Cordero Stormwater System of Guayaquil (Ecuador)

Urban flooding is a major problem in many coastal cities. The rapidly shifting patterns of land use and demographic increase are making conventional approaches to stormwater management fail. In developing countries such as Ecuador, a lack of monitoring, financial constraints and absence of proper policies exacerbate flooding problems. This work assesses the implementation of two Low Impact Development strategies (LIDs), namely, green streets and rain barrels, as nature-based solutions to mitigate flooding problems. The use of the “Stormwater Management Model” (SWMM) helped to contrast the new approach with the current state of the drainage system, including normal and extreme scenarios. With an implementation of 1.4% (19.5 ha) of the total area with LIDs, the reduction of runoff for short events (200 min) is around 20%, and for extreme events (within 24 h) is around 19% in comparison to the conventional approach. Flooded nodes were reduced to 27% for short events, and to 4% for extreme events. The peak flooding system had a reduction to 22% for short events and 15% for extreme events. These highlights help to increase city resilience, and authorities and stakeholders should engage in climate actions to reduce flood risks complementing drainage operations with nature-based solutions. Moreover, calibrated results in this article serve to increase awareness among municipal authorities regarding the importance of maintaining flooding records to improve modelling results for decision-makings processes.

Development and Application of a Real-Time Flood Forecasting System (RTFlood System) in a Tropical Urban Area: A Case Study of Ramkhamhaeng Polder, Bangkok, Thailand

In urban areas of Thailand, and especially in Bangkok, recent flash floods have caused severe damage and prompted a renewed focus to manage their impacts. The development of a real-time warning system could provide timely information to initiate flood management protocols, thereby reducing impacts. Therefore, we developed an innovative real-time flood forecasting system (RTFlood system) and applied it to the Ramkhamhaeng polder in Bangkok, which is particularly vulnerable to flash floods. The RTFlood system consists of three modules. The first module prepared rainfall input data for subsequent use by a hydraulic model. This module used radar rainfall data measured by the Bangkok Metropolitan Administration and developed forecasts using the TITAN (Thunderstorm Identification, Tracking, Analysis, and Nowcasting) rainfall model. The second module provided a real-time task management system that controlled all processes in the RTFlood system, i.e., input data preparation, hydraulic simulation timing, and post-processing of the output data for presentation. The third module provided a model simulation applying the input data from the first and second modules to simulate flash floods. It used a dynamic, conceptual model (PCSWMM, Personal Computer version of the Stormwater Management Model) to represent the drainage systems of the target urban area and predict the inundation areas. The RTFlood system was applied to the Ramkhamhaeng polder to evaluate the system’s accuracy for 116 recent flash floods. The result showed that 61.2% of the flash floods were successfully predicted with accuracy high enough for appropriate pre-warning. Moreover, it indicated that the RTFlood system alerted inundation potential 20 min earlier than separate flood modeling using radar and local rain stations individually. The earlier alert made it possible to decide on explicit flood controls, including pump and canal gate operations.

Incorporating Ecosystem Services into Water Resources Management-Tools, Policies, Promising Pathways

Ecosystems provide a range of services, including water purification, erosion prevention, and flood risk mitigation, that are important to water resource managers. But as a sector, water resources management has been slow to incorporate ecosystem protection and restoration, for a variety of reasons, although related concepts such as nature-based solutions and green infrastructure are gaining traction. We explain some of the existing challenges to wider uptake of the ecosystem services concept in water resources management and introduce some promising avenues for research and practice, elaborated in more detail through 12 papers, spanning five continents and a variety of contexts, which make up a Special Issue on "Incorporating Ecosystem Services into Water Resources Management". Cross-cutting themes include (A) ecosystem services as a flexible concept to communicate with stakeholders; (B) participatory processes to involve stakeholders in research; (C) multiple values, and valuation methods, of water-related services; and (D) applications of decision-support tools. We conclude with a summary of research gaps and emphasize the importance of co-producing knowledge with decision makers and other stakeholders, in order to improve water resources management through the integration of ecosystem services.

Smart City Thailand: Visioning and Design to Enhance Sustainability, Resiliency, and Community Wellbeing

A “Smart City” framework was used to investigate and develop visions of alternative futures for a peri-urban superblock north of Bangkok, Thailand. The Smart City framework considers seven smart pillars: environment, economy, energy, mobility, people, living, and governance, with a focus on community wellbeing that is supported by information and communication technology (ICT). A mixed-method approach that included: community and industry surveys, both online and face-to-face (total n = 770); in depth, semi-structured, stakeholder interviews; passive participant observation; and photo-documentation was used to inform and organize the project visions and designs. Several themes emerged from the community surveys and key stakeholder interviews: (i) connected green space is highly valued and effectively links multiple smart pillars, enhancing community wellbeing and resiliency to flooding; (ii) superblock mobility, connectivity, and sustainable development could be achieved through a seamless, integrated public-transit system following the principles of transit-oriented development (TOD); (iii) the superblock should prepare for the implementation of Thailand 4.0 through the improved programmatic and physical integration of local industry, community, and universities, including plans for a Digital Village and co-work space. Example designs that address these considerations and vision alternative futures for the superblock are presented in this Smart City case study.

The Importance of Water and Climate-Related Aspects in the Quality of Urban Life Assessment

Global challenges such as urbanization, aging societies, climate change, and environmental and water crises are becoming increasingly important in terms of the impact they might have on the quality of life (QoL) in cities. Appraisal instruments for QoL assessment, such as rankings and guides, should therefore include these aspects. The aim of this research was to verify the significance of water and climate-related aspects in assessment tools. A comparative analysis of 24 selected QoL assessment tools shows to what extent these aspects are included in the domains, criteria, and indicators proposed in the instruments. The method of verification is a comparison of the position of winning cities in QoL rankings and city resilience rankings. The results show that water and climate-related aspects are still underestimated in the QoL rankings and guides, and only a few cities with the highest quality of life ranked highly in sustainability and climate resiliency ratings. Our results suggest that the tools for the evaluation and comparison of cities need remodeling, taking into account the most important global risks and Sustainable Development Goals (SDGs), in order to create aging-friendly and climate-neutral cities.