Site-specific Scale Research Articles

A mobility network approach to identify and anticipate large crowd gatherings

The study of large crowd gatherings combines aspects of longer-range human mobility with site-specific pedestrian dynamics. Recently, substantial progress has been made in understanding the collective behaviors of crowds on the site-specific scale. Yet, the human mobility aspect remains vague in terms of how large crowds come together in the first place. Using high-resolution human mobility data in form of millions, potentially real-time, subway and taxi records, our approach uncovers the mobility patterns involved in large crowd gatherings. In addition, we discriminate anomalous mobility fluxes from ordinary mobility fluxes by introducing the concept of anomalous mobility networks, within which nodes are traffic zones and links are defined via the Jensen-Shannon divergence. Our approach allows for easy identification of occurrence, location and developing stages of crowd formation. Strikingly, within the anomalous mobility networks, we find high-stress crowd density to be preceded by a node in-degree kin surpassing the critical threshold kc, typically preceding the maximum crowd density by a couple of hours, enabling us to anticipate large crowd gatherings via a surprisingly simple approach based on the simple network index kin.

A method to develop the input parameter database for site-specific debris flow hazard prediction under extreme rainfall

The predictive hazard analysis at a detailed scale for debris flow runout analysis can be improved significantly through reliable estimation of the input parameters. In this study, a method for database establishment of input parameters at a site-specific scale was laid out for the predictive-based debris flow hazard assessment under extreme rainfall. The adoption of the DAN-3D code necessitated the estimation of three main input parameters: initial volume, bulk basal frictional angle, and growth rate. The initial volume was assessed using a 3D coupled finite element seepage and limit equilibrium-based slope stability analysis. An artificial neural network-based model was developed using 27 debris flow events for predicting the basal bulk frictional angle and consisted of eight factors: plan curvature, profile curvature, percentage of fine content, D50, initial unit weight, initial volume, relative relief ratio, and channel length. Finally, the growth rate was estimated using the previously assessed initial volume, soil depth, and the approximate runout length. The proposed method was validated by application to the Raemian slope in the Woomyeon mountain region, Seoul, for the extreme rainfall event of 27 July 2011. The analysis yielded a final volume of 53,067.9 m3, a velocity upon arrival on the road of 26.81 m/s, and an approximately 0.5-m debris thickness concentrated near the Raemian apartments. The comparison of the predicted debris flow path and debris flow velocity with the actual event demonstrates good similarity and provides a conservative estimate of the volume. This study therefore illustrates the importance of an input parameter database in providing a reliable debris flow runout hazard assessment.

A methodology for ground motion area detection (GMA-D) using A-DInSAR time series in landslide investigations

In recent years, the Advanced Differential Interferometric Synthetic-Aperture Radar (A-DInSAR) technique has advanced rapidly for detecting and monitoring ground surface deformations due to landslides. Identification of the areas affected by ground motion through A-DInSAR data is generally based on visual inspection and hotspot or cluster analysis of average displacement rates. However, interpreting A-DInSAR time series of a particular area can provide a better indication of the real trend of displacement of a landslide, while identifying the possible moment of acceleration of the deformation process as well. In this work, a novel methodology is proposed for identifying different typologies of ground motion areas mainly related to landslide phenomena at a regional scale, by means of A-DinSAR data at high spatial and temporal resolutions. This methodological approach was tested and validated in a wide area of the Piedmont region (northern Italy), by means of RADARSAT and COSMO-SkyMed satellite data, in both ascending and descending modes. These sensors have a high spatial resolution, allowing investigation of a higher number of landslides as compared to that of the older ERS-1/2 and Envisat data. Linear (constant in time displacement) and non-linear (acceleration or deceleration in the displacement rate) trends were recognised, allowing characterisation of the kinematic pattern of a landslide or a portion of it. Local and site-specific scale analyses, performed in an Alpine valley and in two hillslopes representative of the main geological/geomorphological contexts of the study area, validated the results obtained at the regional scale. This supported the interpretation of the driving mechanism for such known landslides, or other geological processes which can cause ground motion along slopes. The developed procedure can allow one to specify priority areas for prevention activities, in order to optimise the costs and benefits of designing a plan to monitor instability phenomena at regional and site-specific scales.

Experimental Identification on Thresholds for Early Warning of Rainfall-induced Failure on Fractured Slopes after Giant Earthquake

Prevention and mitigation of rainfall induced geological hazards after the Ms=8 Wenchuan earthquake on May 12th, 2008 were significant for rebuild of earthquake hit regions. After the Wenchuan earthquake, there were tens of thousands of fractured slopes which were broken and loosened by the ground shaking, they were very susceptible to heavy rainfall and change forms into potential debris flows. In order to carry out this disaster reduction and prediction effectively in Longmenshan region, careful real-time monitoring and pre-warning of mountain hazards in both regional and site-specific scales is reasonable as alternatives in Wenchuan earthquake regions. For pre-warning the failure of fractured slopes induced by rainfall, the threshold value or the critical value of the precipitation of hazards should be proposed. However, the identification of critical criterion and parameters to pre-warning is the most difficult issue in mountainous hazards monitoring and pre-warning system especially in the elusive and massive fractured slopes widespread in Wenchuan earthquake regions. In this study, a natural coseismic fractured landslide in the Taziping village, Hongkou County, Dujianyan City, was selected to conduct the field experimental test, in order to identify the threshold parameters and critical criterion of the fractured slopes of Taziping. After the field experimental test, the correlation of rainfall intensity, rainfall duration and accumulative rainfall was investigated. The field experimental test was capable of identifying the threshold factors for failure of rainfall-induced fractured slopes after the giant earthquake.

Modeling Suburban Phosphorus Runoff and BMPs: Downscaling from Watershed Systems to Site-Specific Scales

AbstractModeling nutrient pollution remains important in assessing and managing impacts on aquatic ecosystems. Phosphorus is a limiting factor in inland water bodies, and there is a need for modeli...

Assessment of Rock Injectivity by Comparing the Open-hole Well Logging Data with Continuous Rock Core

The open-hole well logging data were obtained for the entire trip of the TPCS-M1 deep drilling. In particular, continued PQ size core sampling had been conducted within the depth range from 1505 to 3005 mRT, where recovered intact core length amounted to 1379m in a total. All these drilling activities hence provided a thorough background for elaborate assessment of young rock injectivity in terms of rock permeability. In this paper, the open-hole well logging data and continuous rock coring records (e.g., sandstone, siltstone, shale, and their inter layers) are examined in detail within a logging resolution. The well logging data used in the study combined 6 well log indices, including (1) Gamma ray, (2) resistivity, (3) neutron porosity, (4) self-potential, (5) density, and (6) formation factor respectively. Three approaches for identifying the full depth span permeability of a typical sandstone reservoir of KCL formation (2295∼2450 mRT) are carried out, including: (1) an empirical porosity and permeability relationship established from core tests, (2) a radar diagram plot which reflect the combined effect of relevant well logging data, (3) an artificial neural network (ANN) based on 150 rock porosity test results. The core logging and interpretation of grain size with corresponding neritic sedimentary environment are overlooked together with results of all these approaches to categorize different lithologic zones or units. The criteria comes up with this study will become the guideline for selecting the optimum injection zone (10 meter interval) for pilot test in a site specific scale.

Progress in the micro-perspective studies of economic geography in China since 1980s

Micro-perspective studies on economic geography in China can be classified into geography of the enterprise, geography of the rural household, and small-scale studies on economic activities. Literature on geography of the enterprise includes spatial expansion of the enterprise, industrial location, firm's networks, industrial relocation, industrial clusters, and the relationship between industrial organizations and the environment. Studies on geography of the rural household (GRH) include the theoretical framework of GRH, the locations of rural economic activities, and the interrelation between rural households and geographical environment. Small-scale studies focus on human-land interaction from a land plot perspective, relations between specialized villages and the environment, and regional sustainable development research at site-specific scale. Micro-perspective studies on economic geography attempt to search for the basic unit of economic-geographical landscape, exploring the geographical process and the formation mechanism of geographical phenomena. The exploration of these three perspectives anticipates new approaches to economic-geographical studies with China's special background.

Probabilistic and spatial assessment of liquefaction-induced settlements through multiscale random field models

Evaluation of liquefaction-induced settlements over an extended area requires the integration of different solution models that can account for the liquefaction resistance of a given soil profile and its spatial dependence across scales. In this paper, a CPT-based liquefaction model is adopted to estimate the liquefaction-induced settlement at individual sounding locations. The model is then integrated with multiscale random field models to account for spatial variability of soil properties. One important advantage of the proposed framework is its ability to consistently refine and provide settlement estimations across different scales, from regional and geologic unit scales down to a local, site-specific scale. The proposed methodology is then applied to the Alameda County, California, an earthquake-prone region, to illustrate the procedure for probabilistic and spatial assessment of liquefaction-induced settlements at different scales.

Correlating Site-Scale Erodibility Parameters from Jet Erosion Tests to Soil Physical Properties

Abstract. One of the most commonly used methods of measuring erodibility parameters, i.e., critical shear stress (τc) and erodibility coefficient (kd), of cohesive soils is the Jet Erosion Test (JET). While numerous factors influence the erodibility parameters, the JET provides an in situ measurement technique. However, in many cases where erodibility parameters are required for simulating channel erosion processes, the erodibility parameters are not characterized in situ but estimated empirically based on soil physical properties with relationships that may not be good predictors for all streambanks. The objectives of this study were to investigate the correlation between the erodibility parameters measured with JETs and soil physical properties at a site-specific scale and across three unique streambanks. A total of 74 JETs were conducted within visually homogeneous streambank layers at three sites in Oklahoma along with measurements of soil physical parameters such as texture, bulk density, moisture content, and water and soil temperatures. At the site scale, τc and kd varied by up to three orders of magnitude. Neither multiple linear regressions nor principal components regressions suggested any consistent strongly correlated variables. Therefore, erodibility parameters measured in this study could not be predicted based solely on soil physical properties. It was concluded that τc and kd must be measured in situ and cannot be estimated from empirical relationships due to the heterogeneous nature of soil and the variability in subaerial processes, even within visually homogeneous streambank layers. More research is needed in order to correlate erodibility parameters to other soil parameters and quantify the role of subaerial processes, such as seepage, soil desiccation, and freeze-thaw cycles, on erodibility in order to incorporate spatial variability of erodibility parameters into stability and channel evolution models.

The Impact of Hydrological Parameters on Modelling Slope Safety Factor Towards Shallow Landslides: A Case Study from Oltrepò Pavese

Hydrological monitoring of slope susceptible to shallow landslides allows for identifying the triggering conditions of shallow failures and implementing slope stability analysis at site-specific scale. In this work, a case study of a long-term hydrological monitoring in a slope susceptible to shallow landslides of Oltrepo Pavese (Northern Italy) is presented. The triggering mechanism develops in wet seasons (winter and spring) due to the uprise of a perched water table at about 1 m from ground surface, in consequence of the most intense rainfalls (about > 60 mm in 48 h). Unstable conditions (safety factor < 1.0) are correctly modeled on the basis of both water content and pore water pressure, with a better prediction considering hysteresis effects. Safety factor on the basis of water content can correctly assess the triggering conditions for unsaturated and completely saturated soils. It is possible estimating shallow landslides triggering caused by positive pore water pressures only considering this parameter.

Why geodiversity matters in valuing nature's stage.

Geodiversity--the variability of Earth's surface materials, forms, and physical processes-is an integral part of nature and crucial for sustaining ecosystems and their services. It provides the substrates, landform mosaics, and dynamic physical processes for habitat development and maintenance. By determining the heterogeneity of the physical environment in conjunction with climate interactions, geodiversity has a crucial influence on biodiversity across a wide range of scales. From a literature review, we identified the diverse values of geodiversity; examined examples of the dependencies of biodiversity on geodiversity at a site-specific scale (for geosites <1 km(2) in area); and evaluated various human-induced threats to geosites and geodiversity. We found that geosites are important to biodiversity because they often support rare or unique biota adapted to distinctive environmental conditions or create a diversity of microenvironments that enhance species richness. Conservation of geodiversity in the face of a range of threats is critical both for effective management of nature's stage and for its own particular values. This requires approaches to nature conservation that integrate climate, biodiversity, and geodiversity at all spatial scales.

Evaluating the potential of database technology for documenting environmental change in China's deserts

Despite decades of research, fundamental questions remain about how China's deserts and desert margins function, how they interact with regional and global scale environmental systems, and how they have responded to recent natural and anthropogenic forced climate change. The predominant focus of desert research in China, and globally, has been site specific case studies within sub-disciplines. This highly focused view makes development of a comprehensive interdisciplinary understanding of these deserts difficult. The fields of database creation, data mining and modern statistics have advanced the analysis of complex real-world data, however these methods enjoy only a relatively modest penetration into the geosciences. We report herein on the application of these new technologies to desert environmental systems in China, and illustrate the potential value of well-constructed databases and tool-rich analysis environments at regional, local and site specific scales. Regional analysis suggests significant warm season decrease and cold season increase in cloudiness in China's deserts suggesting that contrasts between cold and warm season cloudiness may be increasing. At a local and site specific scale at central China's Tengger Desert/Helan Mountains climate transition we find a significant climate forced greening of the desert margin over the past decade which may be reversing desertification trends aiding China's remediation efforts. We note that this new approach provides a “living” archive that allows capture of changes currently occurring in China's deserts as well as allowing assessments of human efforts to modify desert and desert margin environments.

Mitigating and adapting to climate change: Multi-functional and multi-scale assessment of green urban infrastructure

In order to develop climate resilient urban areas and reduce emissions, several opportunities exist starting from conscious planning and design of green (and blue) spaces in these landscapes. Green urban infrastructure has been regarded as beneficial, e.g. by balancing water flows, providing thermal comfort. This article explores the existing evidence on the contribution of green spaces to climate change mitigation and adaptation services. We suggest a framework of ecosystem services for systematizing the evidence on the provision of bio-physical benefits (e.g. CO2 sequestration) as well as social and psychological benefits (e.g. improved health) that enable coping with (adaptation) or reducing the adverse effects (mitigation) of climate change. The multi-functional and multi-scale nature of green urban infrastructure complicates the categorization of services and benefits, since in reality the interactions between various benefits are manifold and appear on different scales. We will show the relevance of the benefits from green urban infrastructures on three spatial scales (i.e. city, neighborhood and site specific scales). We will further report on co-benefits and trade-offs between the various services indicating that a benefit could in turn be detrimental in relation to other functions. The manuscript identifies avenues for further research on the role of green urban infrastructure, in different types of cities, climates and social contexts. Our systematic understanding of the bio-physical and social processes defining various services allows targeting stressors that may hamper the provision of green urban infrastructure services in individual behavior as well as in wider planning and environmental management in urban areas.

The relationship between water and air temperature in chironomid-based paleoclimate reconstructions: Records from boreal and subarctic Finland

Fossil remains of larval chironomids are one of the most useful paleolimnological proxies to reconstruct Holocene paleoclimate. We investigate the within-lake distribution of chironomids in relation to water temperature and test the usability of intralake calibration in chironomid-based temperature reconstructions. We compare our findings against the traditional multilake calibration technique in Holocene sediment cores from Finland. The results show that intralake water temperature optima of common taxa correspond closely with mean July air temperature optima in a regional multilake dataset, with exception of a few vegetation-associated taxa. A calibration model based on intralake water temperatures shows performance statistics that correspond to the general performance statistics level of multilake calibration models. However, the intralake model has somewhat increased prediction error. Despite the fact that the intralake model is sensitive to poor modern analogues, it shows correlation with the results using the multilake calibration approach in the Holocene reconstructions. Our results confirm that the within-lake distribution of chironomids along a water depth gradient is closely linked with water temperature gradient. This provides evidence for the close relationship between chironomids and temperature in general and suggests that, in addition to the regional scale, water temperature is a key variable in determining chironomid distribution at the site-specific scale. However, long-term changes in intralake gradients in other depth-related factors, such as hypolimnetic oxygen conditions, extent of photic zone and habitat distribution, may hamper the quantitative accuracy of chironomid-based temperature reconstructions, though the results also suggest that these changes are likely to have little general impact on the trends of chironomid-based air temperature reconstructions.

Mercury hotspot identification in Water Conservation Area 3, Florida, USA

A significant amount of science and effort has been placed on understanding the biogeochemical cycle of mercury within the Florida everglades. The range of resolution for these studies include regional (Everglades Protection Area) and site-specific scales, with very little attention being given to the landscape scale. However, a lot of questions still exist regarding methyl mercury (MeHg) synthesis, bioaccumulation and environmental accumulation. I used the Geti–Ord Gi * spatial clustering statistic to describe and evaluate soil total mercury (THg) and MeHg data collected by U.S. Environmental Protection Agency Regional Environmental Monitoring and Assessment Program between 1995 and 2005. Soil mercury (total and methyl) displayed distinct spatial clustering within Water Conservation Area 3 (WCA3) and was dependent on canal density, water control structure density and hydroperiod. THg hotspots were identified consistently within the southern portion of WCA3A and WCA3B in areas with prolonged hydroperiods (360.9 ± 0.7 days), low canal densities (0.064 ± 0.008 canals/km2) and low structure densities (0.008 ± 0.001 structures/km2). MeHg hotspots consistently occurred within the northern portion of WCA3A and during the last year of sampling in WCA3B. MeHg hotspots occurred in areas with shorter hydroperiods (282.0 ± 8.8 days), lower canal density (0.109 ± 0.013 canals/km2) and higher structure density (0.029 ± 0.005 structures/km2). Results presented in this study provide further understanding to Hg hotspot dependence on hydrological factors and potentially help guide water management decisions.

Development of a customised design flood estimation tool to estimate floods in gauged and ungauged catchments

The estimation of design flood events, i.e., floods characterised by a specific magnitude-frequency relationship, at a particular site in a specific region is necessary for the planning, design and operation of hydraulic structures. Both the occurrence and frequency of flood events, along with the uncertainty involved in the estimation thereof, contribute to the practising engineers’ dilemma to make a single, justifiable decision based on the results obtained from the plethora of ‘outdated’ design flood estimation methods available in South Africa. The objectives of this study were: (i) to review the methods currently used for design flood estimation in South Africa for single-site analysis, (ii) to develop a customised, user-friendly Design Flood Estimation Tool (DFET) containing the latest design rainfall information and recognised estimation methods used in South African flood hydrology, and (iii) to demonstrate the use and functionality of the developed DFET by comparing and assessing the performance of the various design flood estimation methods in gauged catchments with areas ranging from 100 km² to 10 000 km² in the C5 secondary drainage region, South Africa. The results showed that the developed DFET will provide designers with an easy-to-use software tool for the rapid estimation and evaluation of alternative design flood estimation methods currently available in South Africa for applications at a site-specific scale in both gauged/ungauged and small/large catchments. In applying the developed DFET to gauged catchments, the simplified ‘small catchment’ (A ≤ 15 km²) deterministic flood estimation methods provided acceptable results when compared to the probabilistic analyses applicable to all of the catchment sizes and return periods, except for the 2-year return period. Less acceptable results were demonstrated by the ‘medium catchment’ (15 km² &lt; A ≤ 5 000 km²) deterministic and ‘large catchment’ (&gt;5 000 km²) empirical flood estimation methods. It can be concluded that there is no single design flood estimation method that is superior to all other methods used to address the wide variety of flood magnitude-frequency problems that are encountered in practice. Practising engineers’ still have to apply their own experience and knowledge to these particular problems until the gap between flood research and practice in South Africa is narrowed by improving existing (outdated) design flood estimation methods and/or evaluating methods used internationally and developing new methods for application in South Africa.Keywords: Design flood, design rainfall, estimation, ungauged catchments, flood magnitude-frequency

Using a microclimate model to evaluate impacts of climate change on sea turtles

Sea turtles are thought to be particularly vulnerable to climate change as projected increases in temperature may skew the sex ratio of their hatchlings, decrease hatchling success and thus threaten population persistence. Given the seriousness of the threat from climate change it is critical to understand the rate at which soil temperatures at sea turtles’ nesting grounds are likely to change. This has stimulated the development of correlative models to assess and project how projected increases in temperature may impact sea turtle's reproductive output. Correlative models correlate climatic variables to soil temperature and hatchling sex ratio. These models have been widely used due to their simplicity and the flexibility of their data requirement. However, outputs are restricted by the environmental conditions used for the model and thus does not allow exploration of daily variation in sand temperature. Further, the potential error inherent in this approach has not been determined.Researchers working with other animals with temperature-dependent sex determination (TDS) have developed microclimate models to determine nest temperature and potential impacts from climate change. Microclimate models use the interaction between climate, soil, and topography with physiology and nesting behavior of animals to determine future production of hatchling sex ratios. Until now, microclimate models have never been applied to sea turtles and its correlation and consistency with correlative models has never been explored. To address this, we used the Niche Mapper™ microclimate model to project soil temperature at key sea turtle nesting grounds under various scenarios of global warming. Results from the microclimate model are compared to published projections from correlative models. The two approaches accurately and congruently model current soil temperature and project a feminization of the northern Great Barrier Reef green turtle population as climate change progresses. To provide guidance of when to use each approach we also reviewed the applicability and effectiveness of each model. The microclimate model provided a more robust picture of the incubating environment as it has the potential for projecting soil temperature for every hour of the day at various locations and depths within a nesting ground. This allows exploration of whether animals with TDS can counteract the impacts of global warming by changing nest depth and nesting distribution. With time and the validation of the microclimate model with short-term projections, the microclimate model can also be used to refine short-term adaptive management strategies as they can provide explicit recommendations on site-specific scales for translocation of eggs and alteration of the nesting environment.

Coupling statistical and dynamical methods for spatial downscaling of precipitation

The resolution of General Circulation Models (GCMs) is too coarse for climate change impact studies at the catchment or site-specific scales. To overcome this problem, both dynamical and statistical downscaling methods have been developed. Each downscaling method has its advantages and drawbacks, which have been described in great detail in the literature. This paper evaluates the improvement in statistical downscaling (SD) predictive power when using predictors from a Regional Climate Model (RCM) over a GCM for downscaling site-specific precipitation. Our approach uses mixed downscaling, combining both dynamic and statistical methods. Precipitation, a critical element of hydrology studies that is also much more difficult to downscale than temperature, is the only variable evaluated in this study. The SD method selected here uses a stepwise linear regression approach for precipitation quantity and occurrence (similar to the well-known Statistical Downscaling Model (SDSM) and called SDSM-like herein). In addition, a discriminant analysis (DA) was tested to generate precipitation occurrence, and a weather typing approach was used to derive statistical relationships based on weather types, and not only on a seasonal basis as is usually done. The existing data record was separated into a calibration and validation periods. To compare the relative efficiency of the SD approaches, relationships were derived at the same sites using the same predictors at a 300km scale (the National Center for Environmental Prediction (NCEP) reanalysis) and at a 45km scale with data from the limited-area Canadian Regional Climate Model (CRCM) driven by NCEP data at its boundaries. Predictably, using CRCM variables as predictors rather than NCEP data resulted in a much-improved explained variance for precipitation, although it was always less than 50 % overall. For precipitation occurrence, the SDSM-like model slightly overestimated the frequencies of wet and dry periods, while these were well-replicated by the DA-based model. Both the SDSM-like and DA-based models reproduced the percentage of wet days, but the wet and dry statuses for each day were poorly downscaled by both approaches. Overall, precipitation occurrence downscaled by the DA-based model was much better than that predicted by the SDSM-like model. Despite the added complexity, the weather typing approach was not better at downscaling precipitation than approaches without classification. Overall, despite significant improvements in precipitation occurrence prediction by the DA scheme, and even going to finer scales predictors, the SD approach tested here still explained less than 50 % of the total precipitation variance. While going to even smaller scale predictors (10–15 km) might improve results even more, such smaller scales would basically transform the direct outputs of climate models into impact models, thus negating the need for statistical downscaling approaches.

Understanding the Potential Impacts of Global Climate Change on Marsh Birds in the Gulf of Mexico Region

Global climate change is expected to significantly affect coastal ecosystems worldwide. For tidal marsh birds of the Gulf of Mexico, the extent of these impacts on future population dynamics is unknown. Here, we present information on our current understanding of marsh bird responses to climate change, identify gaps in that understanding, and propose ways of improving our ability to predict impacts on avian populations. Our understanding of how Gulf Coast avian populations will respond to environmental drivers such as sea-level rise, precipitation patterns, and hurricanes is limited, and detailed local and regional studies linking avian biology to wetland processes are needed. Impacts of wetland change on marsh bird species will be optimally assessed and forecasted within an adaptive framework, making use of process-driven studies that include models designed to elucidate patterns in avian biology and wetland dynamics. Further, because management and conservation efforts are implemented at local or site-specific scales, we recommend that process-driven studies incorporate hierarchical structures, nesting local efforts within a regional context. Implementing this research program will prove fundamental in furthering our understanding of avian population dynamics within the changing Gulf of Mexico environment.

Failure of infrastructure embankments induced by flooding and seepage: a neglected source of hazard

Abstract. The risk of failure of transportation embankments due to seepage induced by temporary and occasional impoundments taking place on the upstream side as a consequence of exceptional rainfalls is frequently underestimated. These failure events result from a combination of three main factors, i.e. the flooding event, the hydraulic weakness and the geotechnical weakness of the embankment. Based on the case study of a railway embankment in Southern Italy that collapsed in 2005 due to an upstream impoundment that occurred after few hours of a very intense rainfall, the paper describes a methodological approach aimed at assessing hazard of failure of transportation embankments induced by flooding and seepage. In particular, according to hydrological, hydraulic and geotechnical studies performed to define the factors affecting the process of the embankment failure, three subsequent activities are proposed: the historical analysis of flood damages at the watershed scale; and the assessment of the upstream peak impoundment based on hydrological analysis and the embankment stability analysis, these latter to be carried out at the site specific scale. The approach here proposed is planned to be further validated and improved by means of the application to other case studies, characterised by different contexts and embankment structures.