Small Catchment Area Research Articles

Spatially Varying Effect Mechanism of Intermodal Connection on Metro Ridership: Evidence from a Polycentric Megacity with Multilevel Ring Roads

Understanding the spatially varying effect mechanism of intermodal connection on metro ridership helps policymakers develop differentiated interventions to promote metro usage, especially for megacities with multiple city sub-centers and ring roads. Using multiple datasets in Shanghai, this study combines Light Gradient Boosting Machine (LightGBM) with Shapley additive explanations (SHAP) to explore these effects with the consideration of the built environment and metro network topology. Results show that the collective impacts of intermodal connection are positive, not only within the main city but also alongside the main commuting corridors, while negative effects occur in the peripheral area. Specifically, bike sharing trips increase metro ridership within the inner ring of the city, while bus services lower metro usage at stations alongside the elevated ring roads. Parking facilities enable metro usage at city sub-centers, and the small pedestrian catchment area increases metro riders alongside the main commuting corridors. Empirical findings help policymakers understand the effect mechanism of intermodal connection for stations in different regions and prioritize customized planning strategies.

Soil bacterial communities affected by land-use types in a small catchment area of the Balaton Uplands (Hungary).

Changes resulting from different tillage practices can affect the structure of microbial communities, thereby altering soil ecosystems and their functioning. The aim of this study was to explore and compare the physical, chemical properties and bacterial community composition of soils from different land use types (forest, grassland, vineyard, and arable field) in a small catchment. 16S rRNA gene-based amplicon sequencing was used to reveal the taxonomic diversity of summer and autumn soil samples taken from two different slope positions. The greater the anthropogenic impact was on the type of land use, the greater the change was in soil physical and chemical parameters. All sample types were dominated by the phyla Pseudomonadota, Acidobacteriota, Actinobacteriota, Bacteroidota and Verrucomicrobiota. Differences in the relative abundance of various bacterial taxa reflected the different land use types, the seasonality, and the topography. These diversity changes were consistent with the differences in soil properties.

Distribution and Stabilization Mechanisms of Stable Landslide Dams

Landslide dams, especially stable landslide dams, have been recognised as important contributors to regional geomorphological evolution. The eastern edge of the Tibetan Plateau provides good conditions for the formation of stable landslide dams. To identify stable landslide dams on the eastern margin of the Tibetan Plateau, the Google Earth Engine (GEE) was first used to map water surfaces in the study area. Then, stable landslide dams were identified using high-precision remote sensing images provided by Google Earth. A field investigation and a sampling of typical stable landslide dams were also adopted to characterise the landslide dams. The results show that 101 stable landslide dams are present in the study area, covering an area of 27.75 × 104 km2. There are four types of stable landslide dams, as follows: (1) landslides, (2) rock avalanches, (3) moraines, and (4) debris flows. The morphological parameters of a dam, which include dam height, dam width, dam volume, and catchment area, can be fitted with different relationship curves, with respect to the number of landslide dams. The source areas of landslide dams are generally located in the upper-middle and upper sections of adjacent mountains. The stability of a landslide dam is mainly controlled by the structure of the dam and the relationship between the dam volume and catchment area. Structurally, large rocks with large particle sizes are difficult to activate using river water and the large gaps between the rocks provide sufficient channels for the flow of river water. In regard to the relationship between the dam volume and catchment area, a river with a small catchment area in the study area is commonly blocked by a large dam volume. This study provides a unique opportunity to study the spatial distribution and clarify the factors influencing the stability of stable landslide dams.

Effects of low salinity water inflow on eelgrass and cultured bivalves in subarctic lagoons: Analysis using hydrodynamic model

Brackish water areas are affected by river inflows and changes in tidal level, resulting in large fluctuations in salinity. Prolonged exposure to low salinity water can have adverse effects on the growth of marine plants and animals. Characteristics of lagoons such as catchment area, bottom topography, and seawater exchange rate with the open ocean vary widely and the horizontal and vertical gradients of salinity and spatio-temporal variability are also diverse. In this study, we evaluated the impact of low salinity water inflows due to heavy rainfall on seagrass and cultured bivalves in two lagoons (Akkeshi-ko Lagoon and Notoro-ko Lagoon), which are located in the subarctic region of Japan and have contrasting geomorphological characteristics. Continuous observations of the physical environment were conducted by installing measurement equipment near the seafloor, and we ran ten year replicate calculations using a three-dimensional high-resolution hydrodynamic model. Simulation results were used to assess the risk of low salinity associated with heavy rainfall to eelgrass and bivalves (oyster, scallop, and clam). The model analysis showed that the magnitude and frequency of exposure to low salinity water varied greatly between and within lagoons. Akkeshi-ko Lagoon, which has a relatively large catchment area and shallow basin, was sometimes exposed to extremely low salinities, which could lead to the mortality of oysters during heavy rains once every few years. In contrast, salinity decline in Notoro-ko Lagoon is negligible even in years with heavy rainfall due to the high volume of water within the lagoon and small catchment area. With projections that the intensity of heavy rainfall will increase due to climate change, this study was able to evaluate the impact of changes in river flow on coastal ecosystems and aquaculture, and we discussed adaptation measures that may be necessary in the future.

Reducing the imperviousness of urban soils to enhance the quality of surface water: obstacles and levers to implementing ecological runoff management in the south of France

Urban pavements, which help to maintain clean and secure streets, generate large amounts of runoff that aggravate flooding and degrade the quality of surface water. In the context of ecological and climatic crisis, they also contribute to the creation of heat islands in cities, as well as hindering biodiversity. So greening cities must be encouraged.Our article highlights the case of Montpellier – Mediterranean Metropolis (Montpellier 3M, Southern France), which is undergoing one of the highest rates of demographic and urban growth in France. It asks questions around the impact of increased construction on the quality of water in small and fragile coastal catchment areas by the Mediterranean. It also examines local collective action in an attempt to identify the brakes and levers on greening initiatives for the effective management of runoff water, encouraged by legislation: de-paving, setting up rain gardens and returning to permeable urban soils.We use empirical material collected during sociological research in addition to hydrological and chemical measurements. Our aim was to elucidate the perspectives of a wide range of stakeholders, since an understanding of these is crucial in adapting blue-green infrastructure to the local context so that it is both efficient and accepted as a legitimate solution. Our examination suggests ways to think democratically about the dismantling of bitumen road paving to slow down urban water flows and thus improve the habitability of Southern European cities in a context of climatic and ecological crisis.

Long-term impact of wastewater effluent discharge on groundwater: Identification of contaminant plume by geochemical, isotopic, and organic tracers' approach

Infiltration of effluents from wastewater treatment plants (WWTP) into groundwater can be a source of Contaminants of Emerging Concern (CECs), such as pharmaceutical compounds, that are not fully removed during the treatment processes. A multi-tracer approach, based on hydrogeochemical, isotopic, and organic tracers, is applied in the Vistrenque Aquifer (Gard, France) to assess the dispersion of such unintentional plumes and its potential implication on groundwater quality for CECs in a small catchment area. In this area, a point source of WWTP effluent causes contaminant infiltration and unintentional transfer to the aquifer. This strong impact of an urban effluent was revealed from the Br/Cl ratio, boron concentrations and δ11B isotopic signature of the groundwater in the direct vicinity of the infiltration point. With increasing distance from that point, dilution with groundwater rapidly attenuates the urban signal from these hydrogeochemical and isotopic tracers. Nevertheless, a gadolinium anomaly, resulting from discharges of urban wastewater containing the contrast agents used for magnetic resonance imaging (MRI), highlights the presence of a wastewater plume further along the flow line, that comes with a series of organic molecules, including pharmaceutical residues. Monitoring persistent or reactive molecules along the plume provides a more detailed understanding of the transfer of CECs into groundwater bodies. This highlights the relevance of pharmaceutical compounds as co-tracers for WWTP plume delineation. The present multi-tracer approach for groundwater resource vulnerability towards CECs allows a more in-depth understanding of contaminant transfer and their fate in groundwater.

Integrating Model Predictive Control With Stormwater System Design: A Cost‐Effective Method of Urban Flood Risk Mitigation During Heavy Rainfall

AbstractThe integration of green‐gray infrastructures with advanced control approaches is revolutionizing the stormwater system retrofitting, emerging as an innovative strategy to mitigate urban flood risks. However, a major challenge lies in balancing the substantial investments of these infrastructure projects with their environmental benefits, such as reduced flooding volume and lower peak flow. Model predictive control (MPC), a dynamic and intelligent control approach, optimizes these environmental benefits but is underutilized in the system design phase for cost‐effectiveness analysis. This study introduces a multi‐scenario model framework that incorporates MPC and other control approaches into stormwater system designs, including the implementation of controlled storage tanks and green infrastructures. This framework provides comprehensive modeling tools for practitioners to evaluate the flood control benefits and costs across various infrastructure designs and control scenarios, ultimately identifying solutions that are both environmentally and economically viable. A case study conducted in a small urban catchment area in Shenzhen City, China, demonstrates the effectiveness of this framework. The results indicate that MPC outperforms other control scenarios, particularly under heavy or extreme rainfall conditions. Notably, MPC not only provides superior environmental benefits but also yields considerable cost savings, ranging from 1,787 to 9,371 USD per hectare compared to static control, equating to a 5% reduction in cost relative to rule‐based control. Such findings suggest that integrating MPC is a cost‐effective alternative to extensive infrastructure expansion for flood management, which significantly enhances the benefit contribution of controlled infrastructures without substantial additional expenses.

Technical note: Comparing three different methods for allocating river points to coarse-resolution hydrological modelling grid cells

Abstract. The allocation of points in a river network to pixels of a coarse-resolution hydrological modelling grid is a well-known issue, especially for hydrologists who use measurements at gauging stations to calibrate and validate distributed hydrological models. To address this issue, the traditional approach involves examining grid cells surrounding the considered river point and selecting the best candidate, based on distance and upstream drainage area as decision criteria. However, recent studies have suggested that focusing on basin boundaries rather than basin areas could prevent many allocation errors, even though the performance gain is rarely assessed. This paper compares different allocation methods and examines their relative performances. Three methods representing various families of methods have been designed: area-based, topology-based and contour-based methods. These methods are implemented to allocate 2580 river points to a 1 km hydrological modelling grid. These points are distributed along the entire hydrographic network of the French southeastern Mediterranean region, covering upstream drainage areas ranging from 5 to 3000 km2. The results indicate that the differences between the methods can be significant, especially for small upstream catchment areas.

Modelling the impact land use change on flood risk: Umia (Spain) and Voglajna (Slovenia) case studies

Accurate quantification and assessment flood hazards is critical for mitigation and prevention. This study proposes a methodological framework for analysing this hazard and its relationship to agricultural and forestry land use. The objective is to obtain an integrative methodology based on the HEC-HMS model and to apply different simulations, with land use changes as indicator in two different study areas, taking into account the different characteristics of each basin and the different regulations of each area. This was done in two river basins, the Umia Basin (north-western Spain) and the Voglajna Basin (eastern Slovenia). The hydrological models obtained showed a very high performance in the calibration and validation periods. In the Umia River Basin agricultural use has priority over forestry, with food security taking precedence over water security. Reforestation only upstream has been shown to be almost as beneficial as reforestation throughout the basin. However, the use of abandoned land currently limits the reduction of peak discharge. Nevertheless, for an event designed with a 100-years return period, a reduction of about 12% was achieved. The increase in agricultural use promoted by the administration could increase this peak by about 6%, thus increasing the flood hazard, but it has been shown that this use on less permeable soils and upstream would not significantly increase this peak (<1% for the event studied). On the other hand, the Voglajna Basin has a smaller catchment area and fragmented land use, and a mosaic landscape. For the 100-years return period the reduction in peak discharge is only few percent compared to the baseline scenario even if 30% of the agricultural land (about 7% of the total area) is changed to forest land use. The information provided by the simulations is a useful indicator that can be incorporated into management plans to ensure appropriate decision making by the administration. Not only for the application of nature-based solutions (NBS) and providing evidence-base for the NBS and the reduction of flood risk, but such information is key when the use changes from forestry to agriculture and vice versa, as it provides tools to ensure food and water security. In both case studies it was demonstrated how stakeholders need to undertake optimal and strategic planning and management in order to reduce the risk of flooding. In turn, the use of this modelling, as well as the calculation of scenarios from a perspective that not only evaluates different land use changes, but also incorporates different regulations, is presented as an innovative and realistic analysis.

The Groundwater Resources in the Mazovian Lowland in Central Poland during the Dry Decade of 2011–2020

This article addresses the issue of droughts in recent years in Poland and their impact on the state of groundwater resources. This paper presents the challenges arising from the increasing demand for the use of groundwater for irrigation in agriculture, supplementing water shortages, and potential threats to the water supply of rural waterworks. The main part of this paper focuses on a small catchment area in the Mazovian Lowland, which is one of the driest regions in the country. This article includes definitions, characteristics, and causes of hydrologic and hydrogeologic droughts during the period 2011–2020. In the discussed area, there is generally one groundwater level of the Quaternary age, primarily recharged by rainfall infiltration, which is utilized by all dug wells and a number of drilled wells. The source material consisted of daily measurements of groundwater levels with a free surface from three piezometers located in different land use areas (forest, agricultural, and sparse development). Additionally, daily flows of the Zagożdżonka River at the Płachty Stare gauge station were examined, where the drying of the riverbed in the upper reaches has been observed in recent years. This study investigated the dynamics of hydrogeologic droughts in renewable groundwater resources and the rate of their decline in relation to hydrologic droughts of surface waters.

Long-term additions of ammonium nitrate to montane forest ecosystems may cause limited soil acidification, even in the presence of soil carbonate

Abstract. Nitrogen (N) deposition has decreased in the last decades in Europe but in many cases remains higher than the critical loads, i.e., higher than what could be considered safe for biodiversity and ecosystem functioning. The main concerns about N deposition are eutrophication and acidification. In a long-term experiment (1994 to present) in a montane (1200 m a.s.l.) coniferous forest in Alptal, central Switzerland, we simulated increased N deposition by adding NH4NO3 to rainwater. This treatment consisted of an additional N input of 22 kg ha−1 yr−1 to the 12 kg ha−1 yr−1 ambient bulk deposition rate or 17 kg N ha−1 yr−1 throughfall rate. The treatment was applied simultaneously to a small catchment area and to plots in a replicated block experiment (n=5). The site has a carbonate-rich parent material and is thus not particularly at risk of acidification. Nevertheless, we examined soil acidification as affected both by ambient and experimentally increased N deposition. In the 2.5 decades since the beginning of the study, nitrate (NO3-) and especially sulfate (SO42-) concentrations decreased in precipitation, while pH increased by slightly more than 1 unit. In the same time period a reduction in pH of the soil was measured. The exchangeable acidity in the soil increased, especially in the N-addition treatment. This was mainly observed on small mounds because the drier mounds are less well buffered than wet depressions. This trend, however, was limited in time, as exchangeable acidity later declined again to reach values not much higher than 26 years before. This was also the case in the N-addition treatment and can be considered a progressive recovery mainly due to the reduced acid inputs and, at this site with a carbonate-rich subsoil, to the biological cycling of base cations. The pH of the runoff from the experimental catchments decreased by 0.3 units, both in the control and under N addition. Decreasing Ca2+ and increasing Al3+ and Fe2+ concentrations in runoff also show that the recovery observed in the exchangeable soil acidity is not yet able to stop the slow acidification of water leaving the catchments. However, with the runoff water pH remaining above 7, this trend is not alarming for water quality or for the health of water bodies. Future monitoring will be necessary to see if and when a recovery takes place in the soil and runoff pH.

Holocene sedimentary history of the Silala River (Antofagasta Region, Chile)

AbstractAssessing past and ongoing climate change in the central Andes is critical for understanding the impact of future environmental changes under anthropogenic warming. Emerging from springs located in Bolivia and flowing into northern Chile's Atacama Desert, the Silala River contains inset, terraced wetland (or in‐stream) deposits that provide a unique opportunity to study the impact of past hydroclimate change in a sensitive groundwater system with a small catchment area. After an initial (late Pleistocene) period of deep incision to form the present ravine, in‐stream wetland fine‐grained deposits formed during three phases of aggradation dated to &gt;8.5–1.9 ka (Unit 1), &gt;0.65–0.2 ka (Unit 2), and &lt;0.2 ka to the recent 20th century (Unit 4). These phases of accumulation were coeval with periods of well‐dated records of elevated groundwater tables throughout northern Chile. Phases of abrupt downcutting occurred due to a lowering of the water table after 1.9 ka and before 0.2 ka. The cycle of erosion and deposition clearly continues to the present as evinced by the very recent (21st century) incision of Unit 4 (&gt;1.5 m in some areas) throughout sectors of the Silala where dried‐out standing vegetation can be seen. Such recent incision may be due to multiple different factors, including recent climate change coupled with intense extraction of groundwater resources by the copper mining industry.This article is categorized under: Human Water &gt; Water Governance Science of Water &gt; Hydrological Processes Science of Water &gt; Water and Environmental Change

Exploring soil property spatial patterns in a small grazed catchment using machine learning

Acquiring comprehensive insights into soil properties at various spatial scales is paramount for effective land management, especially within small catchment areas that often serve as vital pastured landscapes. These regions, characterized by the intricate interplay of agroforestry systems and livestock grazing, face a pressing challenge: mitigating soil degradation while optimizing land productivity. This study aimed to analyze the spatial distribution of eight topsoil (0–5 cm) properties (clay, silt, sand, pH, cation exchange capacity, available potassium, total nitrogen, and soil organic matter) in a small grazed catchment. Four machine learning algorithms—Random Forest (RF), Support Vector Machines (SVM), Cubist, and K-Nearest Neighbors (kNN)—were used. The Boruta algorithm was employed to reduce the dimensionality of environmental covariates. The model’s accuracy was assessed using the Concordance Correlation Coefficient (CCC) and Root Mean Square Error (RMSE). Additionally, uncertainty in predicted maps was quantified and assessed. The results revealed variations in predictive model performance for soil properties. Specifically, kNN excelled for clay, silt, and sand content, while RF performed well for soil pH, CEC, and TN. Cubist and SVM achieved accuracy in predicting AK and SOM, respectively. Clay, silt, CEC, and TN yielded favourable predictions, closely aligning with observations. Conversely, sand content, soil pH, AK, and SOM predictions were slightly less accurate, highlighting areas for improvement. Boruta algorithm streamlined covariate selection, reducing 23 covariates to 10 for clay and 4 for soil pH and AK prediction, enhancing model efficiency. Our study revealed spatial uncertainty patterns mirroring property distributions, with higher uncertainty in areas with elevated content. Model accuracy varied by confidence levels, performing best at intermediate levels and showing increased uncertainty at extremes. These findings offer insights into model capabilities and guide future research in soil property prediction. In conclusion, these results urge more research in small watersheds for soil and territorial management.

Hydrological Potential Mapping to Generate Micro-Hydro Power in Code River

Fossil fuel energy utilization in Indonesia is consider high consisting of 65% coal sources and 20% fuel, while only 15% are generate from new and renewable energy sources. This number is critical due to the commitment to reduce greenhouse gases by 29% or 41% as declared Glasgow in 2021. Alternatives source of energy could be obtained from solar, wind, and water. The energy generate from those sources are consider intermittent, however, water utilization can be optimized by construct several weirs (small-scale reservoirs) to accumulate the rain water as a kinetic energy source to generate electricity. Only some part of the world, especially tropical Indonesia archipelago, has enough rain to generate energy. This research intends to measure the potency of Code River, representing small river in generating micro-hydro power. The Code River is representing a small river on the island of Java as part of the archipelago in Indonesia which has the characteristics of a river, a small water catchment area, and has high discharge input from rainfall because it is in the tropics. The weir is equipped with a penstock pipe, as water intake to the generator. The pipe inner diameter made of high-density polyethylene material can be 200, 300, 400, 500, 700, 800, 1,000 and 1,600 mm. Each pipe size can produce discharges of 0.42, 0.75, 1.62, 2.1, 3.1, 3.5, 6.0 and 24.0 m3/s respectively. The combination of discharge and head height will produce electrical energy (in watts). Based on hydrological modelling consisting of 52 sub-watersheds, the highest electricity production in 2021 is 8,359,218.3 kWh with 800 mm pipe size (3.5 m3/sec discharge). The electricity production is based on reliable discharge between 7-96% which is different for each weir location. In conclusion, the electricity supply for the whole year (100%) is inadequate

RATES OF MODERN DENUDATION OF A SMALL CATCHMENT IN THE MIDDLE MOUNTAIN BELT OF THE GREATER CAUCASUS (CASE STUDY OF THE GITCHE-GIZHGIT CATCHMENT)

The volumes of loose-clastic material moved by modern earth surface processes were quantified for a small mid-mountain catchment area ( F = 1,86 km2), located in the Baksan River basin using a number of independent methods (modeling of erosion and geomorphologic mapping). The total volume of removed material was estimated through the assessment of the thickness of bottom sediments accumulated in a reservoir located in the outlet section of the catchment area. The rates of linear and rill erosion have been found using the results of repeated UAV surveys and the pin method. The rates of rockfall processes are estimated on the basis of repeated ground-based laser scanning. Additionally, published data on the rates of earth surface processes in the mountains were used. Based on the results of field mapping and interpretation of space images, a map of the spatial pattern of leading earth surface processes was compiled. A digital terrain model of the catchment was constructed on the basis of detailed UAV survey. The volume of loose clastic material delivered to the reservoir was estimated using data on the average annual rates of leading earth surface processes, a map of their distribution over the catchment area, and the connectivity index. It has been established that the average annual denudation rate within the catchment area is 0,16 mm/year. At the same time, only about 3-10% of the products of denudation are delivered to the reservoir. The sediment yield, calculated on the basis of the volume of sediments in the reservoir, is 514 t/km2 per year. It is comparable to the sediment yield of small rivers draining the mid-mountain belt of the Alps with similar bedrock lithology, which was calculated using the results of long-term observations of water and sediment discharge at gauging stations.

Assessment of the Feasibility of Implementing a Flash Flood Early Warning System in a Small Catchment Area

The occurrence of flash floods is an increasingly common phenomenon. In many parts of the world, it is associated with an increase in the intensity of rainfall. Reducing the financial and social losses caused by the occurrence of local urban floods is possible through the use of hydrodynamic modeling and real-time flood forecasting. The purpose of this study is to assess the ability of the modeling technique to simulate the flow in a small catchment area and to determine the time remaining to reach the set warning and danger levels. SWMM 5.2 and QuantumGIS software were used in the study. The analysis showed that for the considered catchment area with a short length of the main stream (1612 m), the time possible for implementing countermeasures and evacuating the population is 70 to 120 min. The study also confirmed that short-term rainfall requires less depth to reach high stormwater elevations than long-term rainfall. In addition, a relationship was noted between the preceding rainfall and the height of stormwater and the forecast time. There was an unfavorable reduction in forecasting time as the depth of rainfall increased and its duration shortened. In the case of the analyzed catchment, the maximum elevation of stormwater (Esw,max) is generated by rainfall that is characterized by the highest intensity in the final phase of their duration. Similarly, the longest forecast time (tf) for the maximum stormwater elevation is caused by rainfall, which is characterized by the highest intensity in its final phase. The results of the study can significantly assist local governments when developing a catchment management plan and when trying to implement practices to minimize the negative effects of flash floods.

Context‐specific positive effects of woody riparian vegetation on aquatic invertebrates in rural and urban landscapes

Abstract Woody riparian vegetation (WRV) benefits benthic macroinvertebrates in running waters. However, while some functions are provided by WRV irrespective of surrounding and catchment land use, others are context‐specific. In recent large‐scale studies, effects of WRV on macroinvertebrates were therefore small compared to catchment land use, raising the question about the relevance of WRV for restoration. Model‐based recursive partitioning was used to identify context‐dependent effects of WRV on the macroinvertebrates' ecological status in small (catchment area 10–100 km2) lowland (n = 361) and mountain (n = 748) streams. WRV cover was quantified from orthophotos along the near (500 m) and far (5000 m) upstream river network and used to predict the site's ecological status. Agricultural, urban and woodland cover at the local and catchment scales along with hydromorphology were considered as partitioning variables. In rural agricultural landscapes, the effect of WRV on the ecological status was large, indicating that establishing near‐upstream WRV can improve the ecological status by as much as two of the five classes according to the EU Water Framework Directive. Even in urban landscapes, effects of far‐upstream WRV were large if catchments had a moderate share of agricultural land use in addition. The beneficial effects of WRV were only limited in purely urban catchments or in a multiple stressor context. Synthesis and applications. While woody riparian vegetation (WRV) can even improve the ecological status in urban settings, it is especially relevant for river management in rural agricultural catchments, where developing WRV potentially are effective measures to achieve good ecological status.

Examining income segregation within activity spaces under natural disaster using dynamic mobility network

Rising income segregation perpetuates socioeconomic inequalities, preventing us from developing more sustainable environments. In the literature, little is known about the spatiotemporal dynamics of income segregation under natural disaster. To address this gap, this paper aims to quantify how people experience income segregation in the context of a disaster through their mobility patterns. Specifically, we propose a generalized framework to construct a dynamic mobility network that describes the footprint of residents within their activity spaces, leveraging large-scale mobile phone data. The construction of this network is formulated as a nonlinear programming model and solved by the Lagrangian relaxation and numerical iterative method. A case study is presented to examine income segregation of residents in Harris County (Texas) in access to various critical facilities before, during, and after the winter storm Uri. Our results indicate that income segregation behaviors vary at different critical facilities, as facilities with smaller catchment areas are found to have higher degrees of segregation. We also highlight the disparities in access to critical facilities between low-income and high-income neighborhoods. This paper provides a new venue to better understand income segregation behavior under natural disaster through human mobility networks, which could inform equitable resource allocation in disaster management.

Temporal Variations of Sediment Provenance in a Karst Watershed, China

The environmental quality of the sediments in karst areas is a common concern, and it is of great significance to analyze the sources of the sediments. This study investigates the sources and its temporal variations of catchment sediments in a typical small karst watershed area. Toxic metal concentrations in the catchment area were monitored via three geochemical baseline projects in China. The sediment identification fingerprint tool (SIFT) was used to establish a geochemical model for tracing the main source contributions and its temporal variations of catchment sediments over the past 28 years (1992–2019). The catchment sediments in the small karst catchment area were mainly sourced from the background lithologies, among which limestone contributed the most, followed by dolomite, sand-shale, and mudstone; however, the anthropogenic lead–zinc tailings contributed the least. The contributions and temporal variations of each source were closely related to the lithology, topography, and landform, as well as the change in land-use and vegetation cover and the degree of rocky desertification. Moreover, the implementation of vegetation restoration and control of rocky desertification decreased the contributions of the upstream geological bodies, and the toxic metal content of the catchment sediment decreased accordingly. This study is of great significance for environmental governance in karst areas.

Influence of Landscape and Climate Changes on the Maximum Discharge of Small Catchment Areas

Influence of Landscape and Climate Changes on the Maximum Discharge of Small Catchment Areas