Increase In Impervious Surfaces Research Articles

Detecting Changes in Impervious Surfaces Using Multi-Sensor Satellite Imagery and Machine Learning Methodology in a Metropolitan Area

This study utilizes multi-sensor satellite images and machine learning methodology to analyze urban impervious surfaces, with a particular focus on Nanchang, Jiangxi Province, China. The results indicate that combining multiple optical satellite images (Landsat-8, CBERS-04) with a Synthetic Aperture Radar (SAR) image (Sentinel-1) enhances detection accuracy. The overall accuracy (OA) and kappa coefficients increased from 84.3% to 88.3% and from 89.21% to 92.55%, respectively, compared to the exclusive use of the Landsat-8 image. Notably, the Random Forest algorithm, with its unique dual-random sampling technique for fusing multi-sensor satellite data, outperforms other machine learning methods like Artificial Neural Networks (ANNs), Support Vector Machines (SVMs), Classification and Regression Trees (CARTs), Maximum Likelihood Classification (Max-Likelihood), and Minimum Distance Classification (Min-Distance) in impervious surface extraction efficiency. With additional satellite images from 2015, 2017, and 2020, the impervious surface changes are tracked in the Nanchang metropolitan region. From 2015 to 2021, they record a notable increase in impervious surfaces, signaling a quickened urban expansion. This study observes several impervious surface growth patterns, such as a tendency to concentrate near rivers, and larger areas in the east of Nanchang. While the expansion was mainly southward from 2015 to 2021, by 2021, the growth began spreading northward around the Gan River basin.

Mixtures of long-term exposure to ambient air pollution, built environment and temperature and stroke incidence across Europe

IntroductionThe complex interplay of multiple environmental factors and cardiovascular has scarcely been studied. Within the EXPANSE project, we evaluated the association between long-term exposure to multiple environmental indices and stroke incidence across Europe. MethodsParticipants from three traditional adult cohorts (Germany, Netherlands and Sweden) and four administrative cohorts (Catalonia [region Spain], Rome [city-wide], Greece and Sweden [nationwide]) were followed until incident stroke, death, migration, loss of follow-up or study end. We estimated exposures at residential addresses from different exposure domains: air pollution (nitrogen dioxide (NO2), particulate matter < 2.5 μm (PM2.5), black carbon (BC), ozone), built environment (green/blue spaces, impervious surfaces) and meteorology (seasonal mean and standard deviation of temperatures). Associations between environmental exposures and stroke were estimated in single and multiple-exposure Cox proportional hazard models, and Principal Component (PC) Analyses derived prototypes for specific exposures domains. We carried out random effects meta-analyses by cohort type. ResultsIn over 15 million participants, increased levels of NO2 and BC were associated with increased higher stroke incidence in both cohort types. Increased Normalized Difference Vegetation Index (NDVI) was associated with a lower stroke incidence in both cohort types, whereas an increase in impervious surface was associated with an increase in stroke incidence. The first PC of the air pollution domain (PM2.5, NO2 and BC) was associated with an increase in stroke incidence. For the built environment, higher levels of NDVI and lower levels of impervious surfaces were associated with a protective effect [%change in HR per 1 unit = −2.0 (95 %CI, −5.9;2.0) and −1.1(95 %CI, −2.0; −0.3) for traditional adult and administrative cohorts, respectively]. No clear patterns were observed for distance to blue spaces or temperature parameters. ConclusionsWe observed increased HRs for stroke with exposure to PM2.5, NO2 and BC, lower levels of greenness and higher impervious surface in single and combined exposure models.

Differential Stomatal Responses to Surface Permeability by Sympatric Urban Tree Species Advance Novel Mitigation Strategy for Urban Heat Islands

As urbanization draws more people to metropolitan areas, a steadfast increase in impervious surfaces ultimately contributes to a pronounced urban heat island effect. While city greening strategies to mitigate urban thermal effects often tout street-tree cover expansion, many plant species are susceptible to heat stress, limiting survivorship, primary productivity, and ecosystem services. Our research objective was to characterize how urban imperviousness impacted the photosynthetic traits of four sympatric tree species in Old Town La Verne, California. We found that while Camphor trees (Camphora officinarum) and Carrotwood trees (Cupaniopsis anacardioides) did not differ significantly in photosynthetic traits at sites with impervious and pervious surfaces, both Coast Live Oak trees (Quercus agrifolia) and Olive trees (Olea europaea) showed significant differences in leaf stomatal length and density. Our findings suggest that the photosynthetic traits of some exotic tree species may be less susceptible to surface permeability than either native or floristically indigenous tree species. We propose that urban greening initiatives adopt a temporal strategy for mitigating urban heat island effects, starting with an urban canopy composed of exotic trees more resilient to impervious surfaces and later transitioning to a recombinant canopy ecology of floristically relevant tree species suited for the soil permeability native to southern California.

Optimal Preventive Maintenance, Repair, and Replacement Program for Catch Basins to Reduce Urban Flooding: Integrating Agent-Based Modeling and Monte Carlo Simulation

Urban sprawl has resulted in great losses of vegetation areas, an increase in impervious surfaces, and consequently the direct flow of stormwater into stream channels (i.e., the immediate flow of stormwater into stream channels, in comparison to the indirect flow that is represented by practices aiming to retain stormwater for a certain period of time and treat the polluted stormwater prior to flowing into the stream channels such as detention/retention basins, among others). Stormwater management systems such as catch basins (CBs) are needed to reduce the effect of stormwater runoff. Preventative maintenance, repair, and replacement of CBs are critical to achieve stormwater management best practices. Those practices prevent the blockage of the stormwater system, limit the pollutants in storm sewers, and reduce the risk of flooding. However, no preceding research studies have been conducted to model and simulate the serviceability of CBs and to determine optimal strategies for operating CBs. To that extent, this study establishes a framework to develop and validate an optimal and adaptive maintenance, repair, and overhaul (MRO) strategy for CBs. In relation to that, an agent-based model (ABM) integrated with Monte Carlo simulation was developed for all 560 CBs in New York City’s District 5 and was statistically validated using 99% confidence intervals. The MRO parameters were optimized to minimize the total cost of the system and attain the desired level of serviceability of CBs. Sensitivity analysis was conducted to guide the maintenance planning process of CBs and reveal the effect of the input parameters on the model’s behavior. In addition, ten thousand Monte Carlo iterations were simulated to derive the distributions of the defined parameters. The results proved that in order to minimize the overall cost of repair, maintenance, and replacement of CBs and attain a minimum serviceability threshold of 80%, the following optimal MRO policy needs to be implemented: having seven service crews (where service crews are human resources (i.e., MRO teams) needed to perform the required maintenance, repair, and replacement work), implementing a replacing policy, and replacing CBs after five maintenance periods. The findings revealed that the service crews represent the most critical parameter in affecting the total cost and serviceability of CBs. This research contributes to the existing literature by offering a better knowledge of the management process of CBs and devising optimal MRO strategies for properly operating them. Ultimately, this research helps decision-makers and engineers increase the lifespan of CBs and limit their risks of breakdown, increase their efficiency, and avoid unnecessary costs. The proposed model is flexible and can be implemented to any geographical area and with other model/system parameters, which makes it adaptive for any scenario and area presented by the user. Finally, maintaining stormwater management practices helps in protecting the environment by decreasing the demand on stormwater systems, reducing flooding, protecting people and properties, promoting healthier rivers, and consequently creating more sustainable communities.

Two-dimensional (2D) flood analysis and calibration of stormwater drainage systems using geographic information systems.

In recent years, there has been severe flooding in urban areas as well as coastal and river flooding. Urban flooding is exacerbated by climate change, urbanization, growing population, and the increase of impervious surfaces in urban areas. Stormwater drainage systems that discharge stormwater to a safe location in urban areas are becoming increasingly important. The objective of this study is to analyze and calibrate the flood performance of stormwater drainage systems currently used in the central region of Malatya in a potential flood situation using geographic information systems and the InfoWorks ICM. The model was created using the land use type, buildings, and digital elevation model (DEM), and the analysis was performed by exposing stormwater drainage systems to rainfall events of 5, 10, and 15 min of duration for return periods of 2, 5, and 10 years. The model was then validated using field-observed rainfall and flood data and its performance was evaluated using R2, NSE, RMSE, and MAE metrics. The results showed that the eight stormwater drainage systems currently in operation cannot fully convey stormwater and may pose a risk of loss of life and property in residential areas. In addition, the severity of the flooding was found to increase with an increasing return period.

Assessing the Long-Term Hydrological Effects of Rapid Urbanization in Metropolitan Shanghai, China: The Finer the Landscape Classification, the More Accurate the Modeling?

Rapid urbanization often leads to increase in surface runoff; its modelling is always the focus in the field of land use effect. One of the methodological issues is how to classify the landscape (land use/land cover) in the model. In this study, the long-term hydrological impact assessment (L-THIA) model was used to simulate the change of annual surface runoff during the rapid urbanization in Shanghai since 1965. Two landscape scenarios, based upon land uses and pervious/impervious surfaces, were compared, and the CN values were adjusted to validate the applicability of the two landscape scenarios. The results showed that there was almost no difference between the results based on the two landscape scenarios, and it was suggested that the simplified landscape scenario based upon pervious/impervious surfaces can be workable and efficient, while the land use scenario may not be necessary for the modelling considering its scale of interpretation of remote sensing data. It was found that there was a clear linear relationship between the percentage of impervious surfaces and surface runoff. For every 1% increase in impervious surface, runoff increased by 0.94%. In addition, the effect of precipitation on the modelling was also discussed, which indicated that with the increase in impervious surface percentage, the response of runoff change in both dry year and dry season was more sensitive.

Influencing mechanism of climate and human activities on ecosystem health in the middle reaches of the Yellow River of China

Global and regional environmental changes caused by climate and human activities have profoundly affected terrestrial ecosystem health. Nevertheless, few studies have been deeply dissected the influencing mechanism of climate and human activities on ecosystem health. In this study, the Middle Reaches of the Yellow River (MRYR) was choosed as the study area, and the improved VORS model was adopted to dynamically assess the ecosystem health level in the MRYR. Then, the influence mechanism of climate and human activities on ecosystem health was deeply analyzed. Our results showed: (1) The ecosystem health level in the rapidly urbanized areas, the ecologically fragile areas in the midwest regions and the mountainous - plain transition zone has a dynamic local spatial structure and spatiotemporal interaction process. (2) Topography, land urbanization, economic urbanization, population urbanization, agricultural activities, environmental pollution, and regional policy have a significant effect on the ecosystem health. (3) In the mid-eastern urban agglomerations, the impervious surface increase and the decrease of ecological land use lead to the increased negative effects of potential evapotranspiration on the ecosystem health of urban agglomerations. Topography has a long-term inhibitory effect on urban expansion, which weakens the negative impact of urbanization on mountain ecosystem health. The negative impact of economic urbanization on the mid-eastern shows a “core-edge” structure with Xi'an metropolitan area, Luohe River Basin, Fenhe River Basin, Taiyuan metropolitan area and Zhengzhou metropolitan area as the core. (4) In terms of the interaction between influencing factors, the interaction between climate and human activities on ecosystem health shows significant differences between the east, middle and west.

Analysis of changes of impervious surface area in Ho Chi Minh City and Ba Ria - Vung Tau province

Rapid urban growth causes the increase of impervious surface which was converted from vegetation land. This affects the rate of water penetration into soils, the rise of surface runoff, and the lowering of groundwater levels. The expansion of the impervious surface gives rise to a series of changes in the physical environment, affecting the quality of life of people due to a change in the thermal energy balance. Therefore, the purpose of this study is to analyse of changes of impervious surface area Ho Chi Minh City and Ba Ria - Vung Tau province which is the marine national economic hub in the period of 2009-2020 by using Landsat satellite image data. The main methods used are NDWI, PISI indices and ISODATA algorithm. The results show that the area of impervious surface area of Ho Chi Minh City is very high with 18.5% in 2009 and 35% increasing rate from 2009-2020. There are 75% districts in Ho Chi Minh city having over 50% impervious surface area. Ba Ria-Vung Tau has lower impervious surface area with 5.8% in 2009 but having the incredible increasing rate– over 100%.

Space Accessibility and Equity of Urban Green Space

Urban green space is an essential form of infrastructure for cities, providing a significant spatial guarantee for sustainable urban development, an essential ecological, social, and cultural function, and an important symbol of urban modernisation and civilisation. However, with the development of cities, urban problems are becoming more serious, such as the increase in impervious surfaces and urban heat islands and the decrease in urban green space and liveability. Therefore, this study integrates the theories and methods of landscape ecology and spatial syntax with GIS technology to construct a comprehensive model for examining the spatial accessibility of green spaces based on remote images and landscape pattern indices, using Fuzhou City as the study area. The study then incorporates demographic variables to explore the characteristics of an equitable distribution of urban green space at the street scale. The results show that the accessibility of green space in the urban areas of Fuzhou decreases from the centre to the periphery. From north to south, there is a trend of ‘low-high-low’, with the northern region exhibiting the lowest accessibility, followed by the southeastern region, and then the western region. In terms of spatial equity in green space, Fuzhou has a more significant share of surplus green space provision, both in terms of the number of streets and area. This shows that the surplus of green space in Fuzhou is greater than the deficit and that the distribution of space is fair. We hope this study will not only help people gain a deeper understanding of green space but also provide a reference for their rational planning and management, thereby improving the accessibility and equity of urban green space as well as their quality and configuration. We also expect it to provide valuable theoretical and technical support for the planning of ecological functions and sustainable development.

Response of ecosystem services to impervious surface changes and their scaling effects in Loess Plateau ecological Screen, China

The complexity and fragility of the Yellow River Basin ecosystem limits its economic growth and sustainable social development as a strategic planning area for development in western China. The Chinese government has established the Loess Plateau Ecological Screen (LPES) in the region to eliminate or mitigate the negative ecological impacts of human activities represented by the expansion of impervious surfaces (IS) through active ecological conservation and restoration. However, there are few studies that quantify the effects of impervious surfaces on ecosystem services (ES). To fill this gap, this study takes the LPES in China as an example and explores the response of ES to IS changes and its scale effect from 2000 to 2020. Based on remote sensing, meteorological, soil, hydrological, social, and economic data using GIS spatial analysis techniques. The results show that: From 2000 to 2020, the urbanization of the LPES developed rapidly, and the IS increased rapidly. The increase in IS affected the supply of ES, which decreased with the increase in IS growth rate, and this phenomenon had a scale effect. Overall, except for soil conservation service (SCS) - IS, carbon storage service (C) - IS at the administrative scale, the negative correlation increased with increasing scale, while the opposite was true at the grid scale. There were thresholds for the response of ES to IS, and the thresholds were also influenced by the scale of study. The smaller the scale was, the lower the threshold was. However, there were differences in the ranking of each ES reaching the threshold with increasing IS at the grid-scale and administrative division scale. The ecosystem services composite index (ESCI) was found to be the best indicator for exploring the relationship between IS and ES compared to other single ecosystem services indices, with the largest negative correlation with IS and the least influenced by scale effects. Given the obvious scale effect of IS on ES, this study suggests that the development of ecological management programs at the national level should be macroscopically regulated at the provincial level, with specific measures at smaller grid scales (5 Km × 5 Km) to constrain IS expansion..

A temporospatial assessment of environmental quality in urbanizing Ethiopia

Global environmental quality has been negatively affected by urbanization, particularly vulnerable in the Sub-Saharan Africa. Therefore, understanding the underlying mechanism and driving forces for the change of environmental quality with urbanization process is essential to improve the environmental sustainability. In this study, the compounded night light index (CNLI) and remote sensing ecological index (RSEI) were used respectively to evaluate the urbanization level and environmental quality in Ethiopia from 2010 to 2020. On this basis, a temporospatial assessment framework was proposed, followed by methods of coupling coordination degree, spatial autocorrelation, elasticity, and decomposition. The results showed that 63 out of 690 woredas experienced environmental deterioration. Socioeconomic effect, carbon intensity, and climate change were decomposed as drivers to environmental quality, with socioeconomic effects contributing >68% of environmental improvement, while carbon intensity and climate change were responsible for >51% and >58% of environmental deterioration from 2010 values. Continuous increase in impervious surfaces resulted in a six-fold increase in surface runoff, which raised the flooding risk in sub areas and rural landscapes. This demands reforms of climate strategies and proper livestock management.

Resurrection genomics provides molecular and phenotypic evidence of rapid adaptation to salinization in a keystone aquatic species

Ecologists and evolutionary biologists are increasingly cognizant of rapid adaptation in wild populations. Rapid adaptation to anthropogenic environmental change is critical for maintaining biodiversity and ecosystems services into the future. Anthropogenic salinization of freshwater ecosystems is quickly emerging as a primary threat, which is well documented in the northern temperate ecoregion. Specifically, many northern temperate lakes have undergone extensive salinization because of urbanization and the associated increase in impervious surfaces causing runoff, and the extensive use of road deicing salts (e.g., NaCl). It remains unclear whether increasing salinization will lead to extirpation of species from these systems. Using a "resurrection genomics" approach, we investigated whether the keystone aquatic herbivore, Daphnia pulicaria, has evolved increased salinity tolerance in a severely salinized lake located in Minnesota, USA. Whole-genome resequencing of 54 Daphnia clones from the lake and hatched from resting eggs that represent a 25-y temporal contrast demonstrates that many regions of the genome containing genes related to osmoregulation are under selection in the study population. Tolerance assays of clones revealed that the most recent clones are more tolerant to salinity than older clones; this pattern is concomitant with the temporal pattern of stabilizing salinity in this lake. Together, our results demonstrate that keystone species such as Daphnia can rapidly adapt to increasing freshwater salinization. Further, our results indicate that rapid adaptation to salinity may allow lake Daphnia populations to persist in the face of anthropogenic salinization maintaining the food webs and ecosystem services they support despite global environmental change.

The Impacts of Land Use Changes in Urban Hydrology, Runoff and Flooding: A Review

The issue of Land Use (LU) change has received considerable critical attention because it is one of the most significant factors caused by human activities worldwide. Recent critical changes in this direction have affected urban hydrology. LU change affects water resources and hydrological characteristics such as runoff and urban flooding. The development of LU causes a rapid increase in impermeable surfaces, increasing the flooding rate. LU also plays a vital role in extending water drainage, groundwater intrusion, and flooding during and after rainfall. This paper aims to investigate LU change impacts on runoff and urban flooding. This review focused on most articles, conference papers, and book chapters published in SCOPUS, including Google Scholar. The study was limitation to the last published from 2017-2021 and also extended some published theories for different years published. In addition, in the short and long term, the development of LU affects the environment, and most factors are involved at a catchment level. However, there is a strong relationship between human activities at the catchment level and runoff. The study concluded that LU strongly influences topography and the landscape in arid, semi-arid, and humid zones. This is why runoff and water distribution happen in urban areas. Furthermore, this study found that built-up area is a critical factor that increases urban flood risk, especially in lowlands along floodplains. It is common for the frequency of floods to become more severe due to a rapid increase in impervious surfaces brought on by urbanisation, increasing runoff. The review concludes that runoff affects by catchment size and its condition. Finally, humans can be reduced runoff and flood risk with a sensibility strategy.

Spatiotemporal analysis of land use changes and their trade-offs on the northern slope of the Tianshan Mountains, China

The unprecedented urbanization recently has inevitably intensified the changes in land use morphology. However, current studies on land use primarily analyze a single morphology, ignoring the relationships between different land use morphologies. Taking the northern slope of the Tianshan Mountains (NSTM) as the study area, this article quantifies the spatiotemporal pattern of land use change, and estimates trade-offs and synergies between dominant (patch density, largest patch index, and landscape shape index) and recessive (land use efficiency, land use intensity, and agricultural non-point source pollution) morphologies to fully understand the dynamic characteristics of land use. Results showed bare areas and grassland were always predominant land use types, and land use change from 1990 to 2020 was characterized by the increase of impervious surfaces and the decrease of bare areas. The strongest trade-off was found between largest patch index and land use intensity, while the synergy between landscape shape index and land use intensity was strongest. There are significant disparities in terms of temporal and spatial patterns of trade-offs/synergies. The correlation coefficients in different study periods were much smaller than their estimations in the whole region, and the trade-offs/synergies in the eastern NSTM were basically identical with the whole relationships. The findings reveal the interactions among various land use characteristics, and provide significant references for coordinated land management and regional high-quality development.

Exploring the impact of landscape changes on runoff under climate change and urban development: Implications for landscape ecological engineering in the Yangmei River Basin

The increase in impervious surfaces caused by urbanization and the frequency of precipitation events resulting from climate change significantly impact the hydrological and geomorphological processes of urban watersheds. Landscape changes caused by urban development may affect surface/groundwater generation and circulation processes. In-depth research on the relationship between landscape changes and runoff is a precondition of urban watershed restoration and stormwater management. Taking the Yangmei River Basin as the study area, the storm water management model (SWMM), landscape index, correlation analysis, and the random forest importance measure were integrated to simulate the runoff process under urban development and climate change scenarios and analyze the direction and contribution of landscape composition and configuration to runoff changes. Results indicated that the runoff change rate relative to the reference period under the RCP 4.5 and RCP 8.5 scenarios gradually decreased as the return period increased. Landscape composition and configuration were significantly correlated with runoff change. Specifically, woodland could reduce runoff, while farmland and water bodies positively impacted runoff changes. The higher fragmented landscape pattern was likely to have altered the runoff, while landscape patterns of a larger size, higher concentrations, and a declining richness typically reduced runoff. The random forest importance evaluation demonstrated the significant contributions of Patch Density, Shannon's Diversity Index, and Large Path Index to runoff. By exploring the potential relationship between landscape changes and runoff, urban planners can better understand the runoff process and find feasible ecological landscape optimization schemes, thus strengthening the sustainable management of water resources and enhancing the resilience of cities to climate change.

Multi-scenario simulation of ecological risk assessment based on ecosystem service values in the Beijing-Tianjin-Hebei region

In this study, a framework for ecological risk assessment based on ecosystem service values and risk probability was established. Remote sensing was used to estimate the value of ecosystem services at the regional scale. Considering the natural and anthropogenic factors and using the entropy weight method to assign weights, probability index was constructed. In addition, multiple scenarios based on the ordered weighted averaging (OWA) method were simulated to reduce subjective uncertainty in the assessment. The results showed that the ecosystem service values generated by the gas regulation value accounted for the largest proportion, with a ratio of 46% in the Beijing-Tianjin-Hebei region. From 2005 to 2015, the value of ecosystem services decreased, falling by 2.5 × 107 Yuan. The level of ecological risk was relatively high, with a corresponding area ratio of 32.89%. Spatially, the areas with high risk were concentrated in the southeastern areas, and areas with relatively low risk were distributed in the western and northern areas. This high risk was probably caused by urbanization which was characterized by reduction of farmland and increase in impervious surface. Multi-scenario simulation showed that the areas of unstable ecological risk zones covered 30% and were mainly concentrated in the surroundings of developing cities. In areas of unstable risk distribution, the relationship between development and protection should be considered. This framework increases the reliability and practicability of ecological risk assessment results and has potential application value for regional risk control in the context of urbanization.

A New Methodology for Updating Land Cover Maps in Rapidly Urbanizing Areas of Levying Stormwater Utility Fee

With a steady increase in impervious surfaces due to urbanization in Korea, there is a growing burden and an urgent need to fund better management of nonpoint sources of pollution and stormwater. A prerequisite for securing the necessary financial resources is the determination of basic data for the accurate calculation of impervious surfaces as the basis for estimating the costs of nonpoint source pollution control and billing of stormwater utility fees. This requires the extraction of landcover information in a Geographic Information System (GIS) environment and development of a landcover map that accurately delineates pervious surfaces within impervious surface areas. However, since landcover maps in Korea are generated and updated at irregular intervals, it is difficult to properly track land use changes. To address this problem, this study has developed a new method for the detailed updating of landcover maps in developing urban areas to facilitate the calculation of stormwater utility fees. Sejong City was selected as the study site because it has experienced large-scale land use changes due to the recent relocation of the national administrative capital and continuous urbanization. The methodology proposed in this study is based on various spatial data such as aerial photographs and digital topographic maps and follows four process steps: preprocessing, first and second updates of landcover information, and quality assurance. In a test of this method, a total of 19,049 reclassified items were generated in the first and second updates, affecting a total area of 26.49 km2 within the original landcover map. The accuracy of these updates reached 99.78%, considering the changed areas and rate of change. This study provides fundamental data for further application of a stormwater utility fee policy in Korea. However, further research is required to automate the generation of accurate pervious/impervious maps and develop pertinent guidelines so that individual municipal and provincial governments can generate and update their own pervious/impervious maps as a basis for calculating the impervious surfaces in their regions.

Seasonal flashiness and high frequency discharge events in headwater streams in the North Carolina Piedmont (United States)

AbstractFirst‐order streams are rarely the focus of research even though they play an important hydrological and ecological role in upland landscapes and may be more susceptible to human impacts than larger streams. We studied 16 first‐order streams in the North Carolina Piedmont to examine relationships between land use, discharge, flashiness and conductivity in the headwaters of the Rocky River and McDowell Creek. Stream gauges were installed on each of the 16 headwater streams to provide constant monitoring of stream depth, temperature and specific conductance. Rating curves were created for each site using models that combined field measured and Manning's calculated discharge. Initial attempts to measure flashiness using the Richards‐Baker Index (RBI) indicated that it is not a good proxy for flashiness in small streams because its use of median daily flows do not capture fluctuations that occur over short time periods. Instead, we developed a new method that focused on the number of days each stream flows above its 99th percentile flow (DMQ99). We also examined individual storm events across multiple seasons. We found that headwater streams in the Piedmont are flashier than more commonly gauged second and third order streams because first‐order streams are more directly connected to the landscape. Streams located in suburban areas tend to be flashier than streams in forested areas as a result of the increase in impervious surfaces and the reduction of evapotranspiration (ET) caused by development. Additionally, we found that all streams become flashier in the winter when ET is lower, suggesting important feedbacks between physical and biological systems. All streams experience periodic extreme conductivity events, indicating significantly impaired ecological conditions. More developed basins generally have higher maximum specific conductance compared with less developed basins although streams have significant natural variability as well. Overall, our results indicate that first‐order streams in the Piedmont are highly impacted by development and that extra caution should be exercised when altering landscapes near small streams.

Spatiotemporal Dynamics of Soil Impermeability and Its Impact on the Hydrology of An Urban Basin

The presence of impervious surfaces in catchments interferes with the natural process of infiltration, which has a marked influence on the hydrological cycle, affecting the base flow in rivers and increasing the surface runoff and the magnitude of flood flows. Like many Latin American cities, Loja (located in southern Ecuador) has experienced significant rates of urban growth in recent years, increasing the impervious surfaces in the catchment where it belongs. The aim of this study is to analyze the spatiotemporal dynamics of imperviousness in the study area for the period 1989–2020, using the Normalized Difference Impervious Surface Index (NDISI) and the supervised classification of Landsat images. The effect on flood flows was studied for each timestep using HEC-HMS hydrological model. Additionally, a future scenario of impervious surfaces was generated considering the observed spatiotemporal variability, possible explanatory variables, and logistic regression models. Between 1989 and 2020, there was an increase of 144.12% in impervious surfaces, which corresponds to the population growth of 282.56% that occurred in the same period. The period between 2001 and 2013 was the one that presented the most significant increase (1.06 km2/year). A direct relationship between the increase in impervious surfaces and the increase in flood flows was observed, reaching a significant variation towards the horizon year that could affect the population, for which measures to manage the surface runoff is necessary.

Changing rate of urban creep and urban expansion over time and its impact upon the hydrologic response of a catchment.

Most previous quantitative research conducted on urban creep and urban expansion has focused on small areas, short time periods, case studies with fairly uniform housing stock and demographic makeup, and the characterisation of urban creep and expansion exclusively in terms of impervious area changes without quantification of the consequential hydrological impact, i.e., increase in surface runoff volume and peak flows in a catchment. This study, using satellite imagery, catchment characteristics data, geographic information system and hydrologic modelling, presents, for the first time, a long-term analysis of urban creep and expansion. The case study is the Ouseburn catchment in Newcastle upon Tyne, a wide-ranging catchment made up of rural, suburban and urban areas, over a period of seven decades. The rate of increase of impervious surfaces is found not to be constant in time; the significant impact of this variation on the catchment's hydrologic response is quantified. This has overall caused a substantial flow volume increase in the Ouseburn over the study period, e.g. 48% for a 1 in 5 years rainfall event. The conclusions obtained are likely representative of many large towns and cities across the United Kingdom and the methodology presented can be easily replicated in other study areas.