Recent Progress in Low-Impact Development in South Korea: Water-Management Policies, Challenges and Opportunities

Multi-stage planning of LID-GREI urban drainage systems in response to land-use changes

Long-term planning of urban drainage systems aimed at maintaining the sustainability of urban hydrology remains challenging. In this study, an innovative multi-stage planning framework involving two adaptation pathways for optimizing hybrid low impact development and grey infrastructure (LID-GREI) layouts in opposing chronological orders was explored. The Forward Planning and Backward Planning are adaptation pathways to increase LID in chronological order based on the initial development stage of an urban built-up area and reduce LID in reverse chronological order based on the final development stage, respectively. Two resilience indicators, which considered potential risk scenarios of extreme storms and pipeline failures, were used to evaluate the performance of optimized layouts when land-use changed and evolved over time. Compared these two pathways, Forward Planning made the optimized layouts more economical and resilient in most risk scenarios when land-use changed, while the layouts optimized by Backward Planning showed higher resilience only in the initial stage. Furthermore, a decentralized scheme in Forward Planning was chosen as the optimal solution when taking costs, reliability, resilience, and land-use changes into an overall consideration. Nevertheless, this kind of reverse optimization order offers a novel exploration in planning pathways for discovering the alternative optimization schemes. More comprehensive solutions can be provided to decision-makers. The findings will shed a light on the exploration of optimized layouts in terms of spatial configuration and resilience performance in response to land-use changes. This framework can be used to support long-term investment and planning in urban drainage systems for sustainable stormwater management.

Changes and Characteristics of Green Infrastructure Network Based on Spatio-Temporal Priority

With advancements in urbanization, natural lands are constantly being encroached upon by artificial impervious surfaces, leading to serious ecosystem damage. Calls for Green Infrastructure to address urban environmental issues and resource reallocation are growing. How to optimize Green Infrastructure networks are becoming increasingly important under rapid urbanization. In this study, we used the main city zone in Hangzhou as the study area, and we extracted 2000, 2010 and 2020 land-use data. We used morphological spatial pattern analysis to identify Green Infrastructure landscape types and further extract Green Infrastructure elements. We identified the spatial priority of Green Infrastructure network elements through landscape connectivity evaluation according to ecological importance and development vulnerability. After the construction of a Green Infrastructure network, we analyzed its spatio-temporal characteristics to determine the Green Infrastructure network’s spatial priority. Through spatial prioritization, the gradual construction and optimization of Green Infrastructure networks will help to improve urban green spaces in stages. Smartly coordinating urban growth and ecological protection based on Green Infrastructure spatial prioritization may help improve urban living environments and enhance sustainable urban development capabilities. In conclusion, sources dominate corridors and codes are changing. If sources are fragmented, the integration degree decreases and the first-level source advantage is weakened. The corridor morphology continuously develops, and the corridor structure stabilizes. Second-level corridors gradually replace third-level corridors to guide Green Infrastructure network structure development. Codes present a scatter distribution and tend to average, closely following corridor change.

Development of a Water-Pricing Model for Domestic Water Uses in Dhaka City Using an IWRM Framework

Dhaka city is experiencing high water use and rapid declination of groundwater. The current water price in the city is low and based on a uniform rate. To arrest the resource degradation along with pursuing cost recovery and promoting social equity, this paper develops a new pricing model for domestic water uses using the integrated water resources management principles. The development is accomplished through estimation of domestic water usage, evaluation of current water prices, and assessment of groundwater degradation externalities in the Tejgaon area of the city using both primary and secondary data. Two economic and two environmental externalities are incorporated. The model is based on an increasing block tariff strategy, and the estimated unit prices for the first and second blocks are respectively 5% and 75% higher than the existing price. The model has the potential to reduce the domestic water use in the city by up to 27%, increase the revenue for the Dhaka Water Supply and Sewerage Authority by up to 75%, and reduce the water bill for poor households by up to 67%. The model has a great potential for practical deployment and the concept can also be applied to other cities and water uses.

Flood Risk in Urban Areas: Modelling, Management and Adaptation to Climate Change: A Review

The modelling and management of flood risk in urban areas are increasingly recognized as global challenges. The complexity of these issues is a consequence of the existence of several distinct sources of risk, including not only fluvial, tidal and coastal flooding, but also exposure to urban runoff and local drainage failure, and the various management strategies that can be proposed. The high degree of vulnerability that characterizes such areas is expected to increase in the future due to the effects of climate change, the growth of the population living in cities, and urban densification. An increasing awareness of the socio-economic losses and environmental impact of urban flooding is clearly reflected in the recent expansion of the number of studies related to the modelling and management of urban flooding, sometimes within the framework of adaptation to climate change. The goal of the current paper is to provide a general review of the recent advances in flood-risk modelling and management, while also exploring future perspectives in these fields of research.

A Socio-Economic and Environmental Analysis of the Implementation of Sustainable Urban Drainage Systems in Vega Baja—Alicante (Spain)

One of the territories most affected by flooding in Spain is the district of Vega Baja del Segura, located in the southernmost point of the province of Alicante. The objective of this article is to estimate the socio-economic and environmental efficiency of implementing sustainable urban drainage systems (SUDS) as part of the Vega Baja Nature Plan. This plan seeks to optimise rainfall management by reproducing and restoring the natural hydrological processes altered by the urban development of cities through integrated actions that generate new natural areas to be used and enjoyed by the residents. To this end, a cost–benefit analysis was carried out in accordance with the methodology established by the European Commission, and a social profitability of 4.3% (IRR) was obtained for the project, which shows the social benefit to be gained from its execution.

Willingness to Pay for the Maintenance of Green Infrastructure in Six Chinese Pilot Sponge Cities

Due to the increasingly devastating impact of pluvial flooding on human beings’ lives and properties in cities, the use of green infrastructure to manage stormwater onsite is becoming more popular worldwide. The maintenance of green infrastructure to ensure its function has become one of the most pressing tasks facing policy makers. However, there is limited research regarding the willingness to pay the stormwater fee as a form of maintenance funding. This study utilized contingent valuation data obtained from a survey of 1101 respondents living in six pilot sponge cities in China to estimate the willingness to pay for the green infrastructure maintenance. The findings indicated that two-thirds of all respondents were willing to pay, 17% would like to pay around 6–10 RMB/month (0.95–1.59 US dollars/month), and 17.8% would like to pay more than 20 RMB/month (3.2 US dollars/month). The educational level and age of the respondents were significant determinants of the probability of willingness to pay and the amount they would like to pay. Knowledge of the concept of sponge cities was another significant influencing factor for the willingness to pay, but it did not influence the amount of payment. The findings could help policy makers make better strategies regarding the maintenance of green infrastructure and its costs.

A Need for Standardized Reporting: A Scoping Review of Bioretention Research 2000–2019

Bioretention cells are a type of low-impact development technology that, over the past two decades, have become a critical component of urban stormwater management. Research into bioretention has since proliferated, with disparate aims, intents and metrics used to assess the “performance” of bioretention cells. We conducted a comprehensive, systematic scoping review to answer the question of “How is the field performance of bioretention assessed in the literature?”, with the aim of understanding (1) how is the performance of bioretention defined in the literature? (2) what metrics are used to assess actual and theoretical performance? A review of 320 studies (mostly peer reviewed articles) found that performance was defined in terms of hydrologic controls, while investigations into water quality pathways and mechanisms of contaminant transport and fate and the role of vegetation were lacking; additionally, long term field and continuous modelling studies were limited. Bioretention field research was primarily conducted by a small number of institutions (26 institutions were responsible for 50% of the research) located mainly in high income countries, particularly Australia and the United States. We recommend that the research community (I) provide all original data when reporting results, (II) prioritize investigating the processes that determine bioretention performance and (III) standardize the collection, analysis and reporting of results. This dissemination of information will ensure that gaps in bioretention knowledge can be found and allow for improvements to the performance of bioretention cells around the world.

An analysis of important issues impacting the development of stormwater management systems in Poland

There is a clear trend in the world to increase the use of sustainable drainage systems. In Poland, it is not as much noticeable, and as a consequence, the conventional stormwater system remains the most common method of stormwater management. As part of the research, an assessment of the issues affecting the implementation of sustainable stormwater management systems in an engineering practices was performed. For that purpose the PESTLE analysis was applied. Its results indicate that legal factors are the key for the development of sustainable drainage systems in Poland. The scale of public support and availability of funding is also not without importance. The possibilities of the implementation growth of sustainable drainage systems should be sought in changes in legal regulations regarding stormwater management, while ensuring at the same time an appropriate level of financing for sustainable solutions. In the second stage of the research, stormwater management models used in Poland were identified. The strengths and weaknesses of these models were presented. There were also discussed the potential opportunities and threats associated with their implementation. The balances of positive and negative sides that were created through a SWOT analysis could be treated as the basis for the detailed analyses of the legitimate application of individual systems in specific areas. It is expected that the results of the research will allow formulating clear principles of an innovation policy in the field of stormwater management and appointing objective and transparent criteria for financing individual types of drainage investments.

Urban Sustainable Development Based on the Framework of Sponge City: 71 Case Studies in China

Sponge city is a new urban stormwater management strategy proposed in China, which enables the city to absorb and save stormwater like a sponge, then release stormwater to solve the problems of urban waterlogging and water shortage. However, at present, sponge cities are confronted with such problems as high management cost and low management efficiency, a lack of research on collaborative management between cities and the feasibility of regional cooperation between sponge cities needs to be proved. Therefore, this article puts forward the theory of sponge city regional ecological cooperative management and builds a multivariate cluster analysis model of sponge city and conducts an empirical study on data of 71 Chinese cities. The research results show that under the multi-index linkage system, China’s urban climate and ecological characteristics do have the characteristics of regional agglomeration and the basic conditions of interregional ecological cooperation, which proves the feasibility of the hypothesis of regional cooperation. Therefore, strengthening the ecological cooperation of sponge cities among regional cities is conducive to improving the supply efficiency of ecological environment quality and realizing the sustainable development of cities.