Ground subsidence phenomena in the Delta municipality region (Northern Greece): Geotechnical modeling and validation with Persistent Scatterer Interferometry

Land subsidence is a common phenomenon occurring in several regions worldwide. Persistent subsidencecauses strong consequences on the affected areas and related problems include environmental, economicand social aspects.A set of forty-two Synthetic Aperture Radar (SAR) images, acquired in 1995–2001 by the EuropeanSpace Agency (ESA) satellites ERS1 and ERS2, were processed with Persistent Scatterer Interferometry(PSI) technique to investigate spatial and temporal patterns of deformation in the Delta municipality(Thessaloniki plain, Northern Greece), a deltaic area with a long history of land subsidence related toaquifer system compaction.Exploitation of output products of a PSI analysis, both average LOS (Line of Sight) deformation ratesand displacement time series, revealed a large subsidence area due to intense groundwater withdrawal.Higher displacement velocities have been observed south-west of Kalochori and south of Sindos, fromboth sides of the Gallikos River. In those areas deformation rates of roughly 4.5 cm/yr have been recorded,during the period from 1995 to 2001.Increasing subsidence rates are measured moving toward the mouth of the Gallikos River, where thethickest sequence of compressible Quaternary sediments is observed. Displacement time series retrievedby PSI technique has been compared with the temporal evolution of the deformation as measured bypre-existing leveling surveys, showing a great agreement.A 2-D finite element model has been run along two representative cross sections in the Kalochori area,in order to simulate the observed temporal evolution of subsidence, coupling the geotechnical behaviorof the formations and the piezometric surface level. Finally, results obtained by the subsidence modelhave been positively compared with the PSI-based information on displacement, providing accurate andperfectly verified results.Outcomes of this work demonstrated the potential of repeat-pass satellite SAR interferometry (InSAR)as suitable technique for increasing knowledge about the extent and the rate of the deformations in caseof subsidence events. Moreover, InSAR turned out to be a valuable tool to validate subsidence modelsand represents a cost-efficiency method, alternative to ground-based measurements for investigatingsurface deformation phenomena

Comparison of Static and Dynamic Young’s Modulus of Prasinites

This study aimed to investigate the statistical correlation between the static and dynamic Young’s modulus of prasinites, a metabasic rock type that outcrops at various localities in the southern part of the Attica peninsula. A total of 39 cylindrical specimens was prepared and an extensive experimental program was carried out to determine the static and dynamic deformational properties for each specimen. Using ordinary least squares regression techniques, a new empirical linear equation was established between the aforementioned properties that can be used in the study region, or elsewhere where metabasic rocks with similar characteristics are investigated

Water and the city: exploring links between urban growth and water demand management

Urban water management is currently understood as a socio-technical problem, including both technologies and engineering interventions as well as socioeconomic dimensions and contexts vis-à-vis both end users and institutions. In this framework, perhaps the most important driver of urban water demand, at the intersection between engineering, social and economic domains, is urban growth. This paper examines aspects of the interplay between the dynamics of urban growth and the urban water cycle. Specifically, a cellular automata urban growth model is re-engineered to provide growth patterns at the level of detail needed by an urban water cycle model. The resulting toolkit is able to simulate spatial changes in urban areas while simultaneously estimating their water demand impact under different water demand management scenarios, with an emphasis on distributed technologies whose applicability depends on urban form. The method and tools are tested in the case study of Mesogeia, Greece, and conclusions are drawn, regarding both the performance of the urban growth model and the effectiveness of different urban water management practices.</jats:p

Physical and Anthropogenic Factors Related to Landslide Activity in the Northern Peloponnese, Greece

The geological, geomorphic conditions of a mountainous environment along with precipitation and human activities influence landslide occurrences. In many cases, their relation to landslide events is not well defined. The scope of the present study is to identify the influence of physical and anthropogenic factors in landslide activity. The study area is a mountainous part of the northern Peloponnesus in southern Greece. The existing landslides, lithology, slope angle, rainfall, two types of road network (highway-provincial roads and rural roads) along with land use of the study area are taken into consideration. Each physical and anthropogenic factor is further divided into sub-categories. Statistical analysis of landslide frequency and density, as well as frequency and density ratios, are applied and combined with a geographic information system (GIS) to evaluate the collected data and determine the relationship between physical and anthropogenic factors and landslide activity. The results prove that Plio-Pleistocene fine-grained sediments and flysch, relatively steep slopes (15&deg;&ndash;30&deg;) and a rise in the amount of rainfall increase landslide frequency and density. Additionally, Plio-Pleistocene fine-grained sediments and flysch, as well as schist chert formations, moderate (5&deg;&ndash;15&deg;) and relatively steep slopes (15&deg;&ndash;30&deg;), along with the amount of rainfall of &gt;700 mm are strongly associated with landslide occurrences. The frequency and magnitude of landslides increase in close proximity to roads. Their maximum values are observed within the 50 m buffer zone. This corresponds to a 100 m wide zone along with any type of road corridors, increasing landslide occurrences. In addition, a buffer zone of 75 m or 150 m wide zone along highway and provincial roads, as well as a buffer zone of 100 m or 200 m wide zones along rural roads, are strongly correlated with landslide events. The extensive cultivated land of the study area is strongly related to landslide activity. By contrast, urban areas are poorly related to landslides, because most of them are located in the northern coastal part of the study area where landslides are limited. The results provide information on physical and anthropogenic factors characterizing landslide events in the study area. The applied methodology rapidly estimates areas prone to landslides and it may be utilized for landslide hazard assessment mapping as well as for new and existing land use planning projects

Establishing and Operating (Pilot Phase) a Telemetric Streamflow Monitoring Network in Greece

This paper describes HYDRONET, a telemetry-based prototype of a streamflow monitoring network in the Greek territory, where such data are sparse. HYDRONET provides free and near-real-time online access to data. Instead of commercially available stations, in-house-designed and -built telemetric stations were installed, which reduced the equipment cost by approximately 50%. The labour of hydrometric campaigns was reduced by applying a new maximum-entropy method to estimate the discharge from surface velocity observations. Here, we describe these novelty elements succinctly. The potential of HYDRONET to provide civil protection services is exemplified by a flood warning demonstrator for Kalamata’s City Centre. The network’s operation, including the hydraulic criteria for monitoring site selection, the characteristics of the telemetric equipment, the operational monitoring and hydrometric procedures, and the specifics of data transmission, quality control, and storage are described in detail, along with experiences with problems encountered during this pilot phase.</jats:p

HYDRO-NET: Hydro-telemetric Network for surface waters &amp;#8211; Innovations and Prospects

&amp;lt;p&amp;gt;The Hydro-telemetric Network, &amp;lt;em&amp;gt;HYDRO-NET&amp;lt;/em&amp;gt;, is a pilot streamflow monitoring network established and operated by the Institute for Environmental Research and Sustainable Development of the National Observatory of Athens (NOA) within the HYDRO-NET Project (2018-2021): &amp;lt;em&amp;gt;Hydro-Telemetric Network of Surface Waters: Gauging instruments, smart technologies, installation and operation&amp;lt;/em&amp;gt;. An aim of the project is that HYDRO-NETs&amp;amp;#8217; principles of design, installation and operation will guide establishing of hydrometric networks in the Hellenic territory. HYDRO-NET provides a comprehensive framework for collection, transmission, handling and free use of data that combines technological innovations and advanced scientific methods with efficient use of resources. It particularly responds to the need of estimating the discharge at cross-sections of streams &amp;lt;em&amp;gt;where no prior data exist &amp;lt;/em&amp;gt;by &amp;lt;em&amp;gt;inexpensive means&amp;lt;/em&amp;gt;.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Technological innovations concern the design and construction of a prototype hydro-telemetry system that combines custom built firmware and intelligent measuring technologies with telecommunication at low cost, ~50% the price of a commercial station. This prototype is equipped with an ultrasonic sensor for measuring stage, a thermometer, a GPRS modem, a camera and a data logger (it can also receive input from a rain gauge), and is powered by a solar panel; data and photos are transmitted to NOA&amp;amp;#8217;s server via mobile internet. The systems&amp;amp;#8217; additional advantages are flexibility in programming, low maintenance costs, and the possibility of &amp;lt;em&amp;gt;extending its monitoring capabilities with additional sensors&amp;lt;/em&amp;gt; (&amp;lt;em&amp;gt;e.g. for monitoring water quality, video camera&amp;lt;/em&amp;gt;).&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Progress in streamflow estimation is achieved through the development of a maximum-entropy based method that calculates the discharge, at a cross-section of known bathymetry, using measurements of water stage and surface velocity by SVR (Surface Velocity Radar) and/or video cameras. Rating curves at monitoring stations can be thus constructed by inexpensive field campaigns, and safely under flooding. &amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;HYDRO-NET currently operates 16 hydro-telemetric stations, six of which are of NOA&amp;amp;#8217;s design, in the Peloponnese and in Attica, Greece. Measured data are transmitted to NOAs&amp;amp;#8217; Server, where they are automatically processed (Quality Controlled) and stored in a Data Base; the data are freely available to users through the OpenHi.net platform (openhi.net), or upon request ([email protected]). A prime service prospect of the HYDRO-NET system, with its real-time observations, is Flood Warning.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Acknowledgment: The Hellenic General Secretariat for Research &amp;amp; Technology has provided financial support, under the National Strategic Reference Framework (2014-2020), for the project HYDRO-NET: Hydro-Telemetric Networks of Surface Waters: Gauging instruments, smart technologies, installation and operation, as a part of the &amp;lt;em&amp;gt;Hellenic Integrated Marine and Inland Water Observing, Forecasting and Offshore Technology System&amp;lt;/em&amp;gt;, HIMIOFoTS (MIS5002739) (https://www.himiofots.gr/).&amp;lt;/p&amp;gt;</jats:p