A city's spatial footprint is covered by extensive impervious building roofs and paved surfaces, which contribute to greater storm-water runoff, more surface pollutants, and less carbon sequestration, hence, worse ecosystem services. This research conducts an empirical study on the ecological and economic impacts of a citywide adoption of green roofs and permeable pavements in Corvallis, OR. The effects on ecosystem services of using green roofs and pervious pavements for a low impact development are modelled using Integrated Value of Ecosystem Services Trade-offs and compared to those from the City's current conventional development without green roofs and pervious pavements. The differences are analysed for ecological impact by storm-water yield, storm-water purification, and carbon sequestration and economic impact by a cost-benefit comparison. The results indicate that low impact development, especially intensive green roofs on commercial/industrial buildings and permeable pavements for parking lots, plays a significant role, even with a higher initial implementation cost, for long-term urban sustainability.

Natural disasters are hazardous geophysical, meteorological, hydrological, climatological, and/or biological events that disturb human and natural environments, causing injuries, casualties, property damages, and business interruptions. Sound analysis is required regarding the effective hazard preparedness for, response to, mitigation of, and recovery from natural disasters. This research proposes an expected risk analysis model of world natural disasters recorded for 1900–2015 in the Emergency Disaster Database compiled by the Centre for Research on the Epidemiology of Disaster. The model produces consistent estimates of country-level risks in terms of human casualty and economic loss. The expected risks, along with their standard deviations, and ranks for world 208 countries, are analyzed with highlights for the top 10, 20 and 30 countries. Normalized expected risks by country population density and per capita gross domestic product (GDP) are also analyzed to further understand the relationships between risks and socio-economic measures. The results show that the model is a reasonably effective alternative to the existing risk analysis methods, based on the high correlations between the observed and estimated total risks. While riskier countries with higher expected risks and standard deviations are found in all continents, some developing countries such as China, India, Bangladesh, and Brazil, or developed countries, such as the United States, Japan, and Germany, are the hot-spots of global natural disasters. The model can be used as a new alternative approach to conduct country-level risk assessments or risk analyses of fatality, injured, affected, and damage—especially for countries’ governments to make sound disaster preparation, and mitigation decisions, sustainable policies, or plans regarding natural disasters.

Using the City of Corvallis, Oregon, a small to medium sized American city, as a test-bed, this paper examines the City’s urban growth in relation to urban accessibility. This relationship is explored in an anatomic spatial-temporal fashion, taking account of: the number and size of developed land use parcels over time; urban accessibility from residential to non-residential land use areas; and the statistical relationships between urban form and urban accessibility. This investigation of land use is structured around use-classification and examined within a range of dimensional and demographic measurements over 5-year time periods from 1853 to 2014; concurrently, urban accessibility is measured by the least-cost path distance as calculated through the OD cost matrix analysis in GIS. The results indicate that the city grew spatially at different rates and its urban accessibility experienced both ups and downs over time. The city’s population growth corresponded closely with urban growth and its decreasing population density negatively impacted on the city’s urban accessibility to commerce, industry, and office for most time periods. Significantly, while the urban density increased steadily after 1950s concurrent with an increase in urban sprawl, in contrast to previous studies on the metropolitan condition, the urban density had no evident impact on urban accessibility in Corvallis. Instead, increasing the land-use mix was a more effective and feasible approach to reduce urban travel path distance and enhance accessibility than increasing population density or urban development density. Accordingly, this research provides evidence-based policy recommendations for planning sustainable urban mobility and urban form in small to medium-sized cities.

Nature-based solutions are some of the most effective strategies to promote sustainable city development; however, existing research on NbS is mostly comprised of single variable studies rather than multiple variables. The purpose of this study was to explore the possibility of extending the NbS of a single variable to two variables for the better development of sustainable cities. Both forestation and wetland restoration are regarded as NbS for sustainable city development. The research approach of “forest–wetland” NbS was proposed and centers on the process and core issues of traditional NbS. Taking Tianjin as an example, the spatial patterns of forests and wetlands, correlation between the spatial distribution of forests and wetlands, and spatial correlation between the areas of forest growth and wetland growth within a certain distance in different years were studied using a spatial distribution pattern analysis, geographic concentration analysis, kernel density estimation and spatial autocorrelation analysis. Based on the core issues of NbS and the above spatial analysis, a “forest–wetland” spatial planning strategy was formulated. The main conclusions are as follows: forest and wetland were negatively correlated in the whole area of Tianjin, forest resources w mainly located in north, while wetland resources were mainly located in south. Compared with forests, the spatial distribution of wetlands in Tianjin was more balanced. There exist synergy and trade-offs between forest and wetland area under certain circumstances. Growth of forests was positively correlated with the growth of wetlands, within a distance of 0–400 m from 2000 to 2010, and within a distance of 0–600 m from 2010 to 2020. An increase in forest area will lead to an increase in evaporation, which in turn will hinder the growth of wetlands in Tianjin. Forest–wetland ecological network could promote synergistic between forest and wetland, and grey infrastructure to reduce potential trade-off between forest and wetland.

In this research, we developed a novel model framework consisting of data mining (DM), linear programming (LP), and an all-or-nothing (AON) flow assignment to estimate maritime freight flows between the United States and the rest of the world. We first built DM and LP models to select and combine various country-level data sources on import and export freight into a complete geographic information system (GIS)-based origin and destination (OD) database with targeted locations, networks, and attributes on ocean routes connecting foreign and U.S. maritime ports. Then, we performed freight assignments and estimated total or commodity-specific import and export freight flows. Additionally, we visualized major sea ports with various handling capacities and optimal maritime freight flows in 2D in GIS and in 3D in Google Earth with highlights for selected total and most imported or exported goods on maritime networks and for major trading partners, such as the U.S. and China. Finally, a visual validation of model results on optimal maritime routes with respect to real-time vessel density network links and routes was provided as well.