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History of Floods in Greece: Causes and Measures for Protection
Abstract
Floods as diachronic and international phenomena affect numerous people, building and infrastructure. Throughout human history, floods are the most lethal and have caused more economic losses than other natural disasters. In this review the history of floods in ancient Greece since the early Bronze Age is presented. Generally, ancient Greeks avoided living near rivers probably for protection from floods and water related diseases. Representative impressive hydraulic anti flooding works including dams, walls, channels from different cities in the Minoan era, and the Archaic, Classical, Hellenistic, and Roman period are presented. It is concluded that the hazards with respect to flood events are more severe today than in ancient times. The ongoing urbanization through the centuries has led to an increasing and unmanageable flood risk. For this reason, a set of special measures should be applied in vulnerable areas aiming to mitigate severe damages that floods might cause, including anti-flooding dams, rainwater harvesting and rain gardens for stormwater retention, reforestation, and other smart environmental strategies.
Flooding is Ghana's most occurrent natural disaster, with Accra, the capital city and central economic hub experiencing the highest flood incidence and the effects on lives and properties. With the increasing trend of data on rainfall above 20 mm (heavy rain) in Accra from 1980 to 2020, a high possibility of future flood hazards has been projected, with the frequency and intensity of flood occurrences expected to increase. Thus, this study aimed to analyze the flood disaster risk perception of urban households in Accra and how it influences their willingness to leave the flood-prone zone. The multinomial probit model was used to analyze the evacuation willingness of households, and binary logit and probit models were also used to test the robustness of the estimates. The results indicate that the odds of being flood risk lovers are found to be decreased by the number of years of formal education, gender, household level of income, physical mobility, costs incurred from previous floods, probability and severity of future floods, and perception about taxing building in flood zones. The odds of being flood risk lovers are increased by household duration in the flood zone, size of household, the experience of past flood occurrences, close distance to work, and residence close to Odaw river/Korle lagoon. The study suggests that policies should target increasing public awareness of flood risks, providing affordable housing for residents, banning new settlements on flood-prone zones, and building infrastructure to mitigate flood risks.
At the beginning of the 21 st Century a research-to-operations program was initiated to design and develop operational systems to support local forecasters in their challenging task to provide advance warning for flash floods worldwide. Twenty some years later, the Flash Flood Guidance System with global coverage provides real-time assessment and guidance products to more than 60 countries, serving nearly 3 billion people. The implementation domains cover a wide range of hydroclimatological, geomorphological and land-use regimes worldwide. This flexible and evolving system combines meteorology and hydrology data and concepts as well as supports product utility for flash-flood disaster mitigation on very large scales with high spatial and temporal resolution. Through quality control procedures, it integrates remotely-sensed data of land-surface precipitation and of land-surface properties from geostationary and polar orbiter satellite platforms, reflectivity data from a variety of weather radar systems, as well as asynchronous precipitation data from ground-based automated precipitation gauges, in order to produce assessments and short-term forecasts that support forecasters and disaster managers in real time. For each region, it also integrates mesoscale meteorological model forecasts with land-surface model response to produce longer-term guidance products. It contains components and interfaces that allow real-time forecaster adjustments to products based on local last-minute field information and relevant forecaster experience. Assessments of utility for flash flood warning operations by national forecasting agencies worldwide are positive. The article exemplifies the process of realization and evolution of the FFGS from research in interdisciplinary fields to operations in diverse environments, and discusses lessons learned.
Exploration of the history and archaeology of the frontier of the Byzantine East.
Floods are one of the most common natural disasters and are extremely dangerous in a global range since they can cause extensive damage to properties or losses in human lives. According to the opinion of many expert scientists, climate change has led to the increase of flooding phenomena over the last years worldwide, as well as in Greece. The aim of this paper is to examine the flooding event that occurred in Mandra area, Attica (Greece) on 14-15 November of 2017. The peak discharge of the Agia Ekaterini and Soures streams was calculated using the rational method (Giandotti) for return periods equal to 10, 100 and 1000 years. The stream characteristics were studied and their behavior during the flood was investigated. Many of the impacts were attributed to the human intervention in the streambeds.
A new integrated national scale flood hazard mapping method based on GIS and ANN techniques • This study provides, for the first time, a flood hazard map for entire Greece. • The methodology was validated based on historical flood events. • 24% of the total area of Greece is under very high flood hazard (50-year return period). Editor: Simon Pollard The present work introduces a national scale flood hazard assessment methodology, using multi-criteria analysis and artificial neural networks (ANNs) techniques in a GIS environment. The proposed methodology was applied in Greece, where flash floods are a relatively frequent phenomenon and it has become more intense over the last decades, causing significant damages in rural and urban sectors. In order the most prone flooding areas to be identified, seven factor-maps (that are directly related to flood generation) were combined in a GIS environment. These factor-maps are: a) the Flow accumulation (F), b) the Land use (L), c) the Altitude (A), b) the Slope (S), e) the soil Erodibility (E), f) the Rainfall intensity (R), and g) the available water Capacity (C). The name to the proposed method is " FLASERC ". The flood hazard for each one of these factors is classified into five categories: Very low, low, moderate, high, and very high. The above factors are combined and processed using the appropriate ANN algorithm tool. For the ANN training process spatial distribution of historical flooded points in Greece within the five different flood hazard categories of the aforementioned seven factor-maps were combined. In this way, the overall flood hazard map for Greece was determined. The final results are verified using additional historical flood events that have occurred in Greece over the last 100 years. In addition, an overview of flood protection measures and adaptation policy approaches were proposed for agricultural and urban areas located at very high flood hazard areas.
Sanitation and hygiene technologies have existed in ancient Hellas since the Bronze Age (ca. 3200– 1100BC), when extensive sewerage and drainage and other elaborate sanitary structures were known in Minoan palaces and towns. Classical and Hellenistic periods should be considered as the most progressive eras in the design of sanitary engineering. At that time anatomically shaped toilet seats are found in several sites since many private houses and public buildings have them. As cities grew in size the pressure of larger populations resulted in the construction of communal toilets with seats that were more densely packed together. Drainage and sewerage systems and sanitary installations reflect high cultural and technological levels and they are associated with contemporary observations and ideas about hygiene and medicine. Before the Hellenic advances, medicine was entirely confined to religious beliefs and metaphysical rituals. In the early Roman period, the knowledge of the ancient world on hygienic matter was incorporated in legislative rules. Despite the weakening of this legislation through the ages, the sanitation practices kept being applied even via a technical tradition of the masons. Later various rulers of the Hellenic world (Europeans or Ottomans), introduced their practices (traditional/scientific) sanitation in the greater Helladic regions.
Groundwater has been utilized since the Prehistoric times. Water supply of some Minoan settlements on the eastern side of the island of Crete (Greece) was based on groundwater. Later on, many wells were constructed in several areas of Greece and their use expanded through subsequent periods. The greatest achievement in groundwater exploitation by ancient Greeks was the construction of long underground galleries or qanats, which collected water from springs and alluvial deposits. In Classical times, most of the wells were on private properties and their owners were forced by regulations to maintain the wells in good condition and ready for use in wartime. During that period, the first scientific theories of Aristotle and Theophrastus were developed in regards to hydrological phenomena, and the processes involved in the formation of surface water and groundwater were clarified. Wells played a major part in urban water supply during the Roman period, in which famous aqueducts were constructed to transfer water; however, several regions of Greece were self-sufficient in water, supplied by many wells from the Prehistoric to the Byzantine period. People understood the local geological conditions and, according to their culture, constructed and managed their own types of wells. In addition to the wells and aqueducts, the hydraulic technology included cisterns to store rainwater, and systems to capture spring water for transport by aqueducts. The examples of hydro-technologies and water management practices described in this paper may have some relevance for water engineering even in modern times.
The present study introduces a multi-criteria index to assess flood hazard areas in a regional scale. Accordingly, a Flood Hazard Index (FHI) has been defined and a spatial analysis in a GIS environment has been applied for the estimation of its value.
The developed methodology processes information of seven parameters namely flow accumulation, distance from the drainage network, elevation, land use, rainfall intensity and geology. The initials of these criteria gave the name to the developed method: “FIGUSED”. The relative importance of each parameter for the occurrence and severity of flood has been connected to weight values. These values are calculated following an “Analytical Hierarchy Process”, a method originally developed for the solution of Operational Research problems. According to their weight values, information of the different parameters is superimposed, resulting to flood hazard mapping. The accuracy of the method has been supported by a sensitivity analysis that examines a range for the weights' values and corresponding to alternative scenarios.
The presented methodology has been applied to an area in north-eastern Greece, where recurring flood events have appeared. Initially FIGUSED method resulted to a Flood Hazard Index (FHI) and a corresponding flood map. A sensitivity analysis on the parameters' values revealed some interesting information on the relative importance of each criterion, presented and commented in the Discussion section. Moreover, the sensitivity analysis concluded to a revised index FHIS (methodology named FIGUSED-S) and flood mapping, supporting the robustness of FIGUSED methodology. A comparison of the outcome with records of historical flood events confirmed that the proposed methodology provides valid results.
The use of water cisterns has been traced back to the Neolithic Age; this paper thus presents a brief historical development of water cisterns worldwide over the last 5500 years. This paper is not an exhaustive presentation of all that is known today about water cisterns, but rather provides some characteristic examples of cistern technology in a chronological manner extending from prehistoric times to the present. The examples of water cistern technologies and management practices given in this paper may have some importance for water resource sustainability for the present and future. Cisterns have been used to store both rainfall runoff water and aqueduct water originating in springs and streams for the purpose of meeting water needs through seasonal variations. Cisterns have ranged in construction from simple clay pots to large underground structures.
Flooding is one of the most important types of disasters in southern Europe recording many victims and extended damages over the last century. The increased pressure for urban expansion together with the high population density has increased flood risk considerably in the region. Greece is not an exception in this regime, having a very rich flooding record since the ancient times. In this work, an extensive catalogue of flooding phenomena during the last 130 years in Greece has been compiled based on numerous sources. Based on this record the temporal and spatial distribution of flood events and victims was examined. In total, 545 events were identified, causing 686 human casualties and inflicting extensive damage across the country. Results showed seasonality patterns with more events clustering in November. They also showed that urban envi-ronments tend to present a higher flood recurrence rates than mountainous and rural areas. An increasing trend in reported flood event numbers during the last decades was discov-ered, even though the number of human casualties remains relatively stable during the same period. Moreover, spatial patterns were identified highlighting areas and administ-rational entities with higher flood recurrence rates across the country.
The evolution of urban water management in ancient Greece, beginning in Crete during the early Minoan period, resulted in a variety of remarkable developments on both the mainland and islands of Greece. Important developments include the implementation of hygienic living standards, advanced hydraulic technologies for water transportation, constructions for flood and sediment control, and sustainable urban water management practices, which can be compared to modem-day practices. The evolution of water management was also related to sociopolitical conditions. During oligarchic periods the emphasis was on the construction of large-scale hydraulic projects, whereas in democratic periods the focus of water management was on sustainable small-scale, safe, and cost-efficient management practices and institutional arrangements related to both the private and public sectors. Such practices and institutions are relevant even today, as the water-related problems of modem societies are not very different from those in antiquity.
Flooding is one of the most important types of disasters in southern Greece with many victims and extended damages over the
last century. The increase in population together with the augmented pressure for urban expansion has increased flood risk
during the last decades considerably across southern Europe. Peloponnese is not an exception in this regime, recording a significant
amount of flood events and casualties. In this work, a catalogue of flooding phenomena during the period 1896-2010 in Peloponnese
has been compiled based on numerous sources. Based on this record the temporal and spatial distribution of flood events and
victims was examined. In total, 102 events were identified, causing 57 human casualties and inflicting extensive damage across
the study area. Results showed seasonality patterns with more events clustering in November. They also showed that urban and
coastal environments tend to present higher flood recurrence rates than mountainous and rural areas. An increasing trend in
reported flood event numbers and casualties during the last decades was discovered. Moreover, spatial patterns were identified
highlighting areas with higher flood recurrence rates across the region studied.
The status of urban sewerage and stormwater drainage systems in ancient Greece is reviewed, based on the results of archaeological studies of the 20th century. Emphasis is given to the construction, operation, and management of sewerage and stormwater drainage systems during the Minoan period (2nd millennium B.C.). The achievements of this period in dealing with the hygienic and the functional requirements of palaces and cities, were so advanced that they can only be compared to modern urban water systems, developed in Europe and North America in the second half of the 19th century A.D. The advanced Minoan technologies were exported to all parts of Greece in later periods of the Greek civilization, i.e. in Mycenaean, Archaic, Classical, and Hellenistic periods.
From the earliest times, Greek societies prepared legislation to solve disputes, define access to the water resources, and regulate waste- and storm-water disposal. On the one hand, evidence suggests that in Greek antiquity (750–30 BC), scientific progress was an important agent in the development of water management in some cities including institutional and regulatory issues. In most cities, it seems not to have been a prerequisite in relation to basic agricultural or household requirements. Previous studies suggest that judicial insight rather than practical knowledge of water management became a vital part of how socio-political and religious organizations dealing with water management functioned. The evidence indicates an interest in institutional matters, but in some instances also in the day-to-day handling of water issues. Thus, the aim of this review is to follow the development of water law and institutions and their technical solutions in the Greek states during the Archaic through the Roman periods. In addition, it demonstrates that the need for water management regulations is not a modern creation, but there is a long tradition of solving complex issues of water supply and use with rather sophisticated legal measures.
Design Drainage and Storm Water Management Systems Efficiently. Urban Storm Water Management, Second Edition covers the design, installation, and maintenance of storm water management systems, addresses the impact of urban development on runoff and infiltration, and focuses on storm water management relative to flooding and water pollution. Recognizing that urbanization increases and accelerates runoff, reduces infiltration, and deteriorates water quality, the author proposes storm water runoff as a resource that can be conserved for reuse. He suggests the reuse of storm water runoff in general, and rainwater from roofs in particular, as a cost-effective means to achieve long-term sustainability. In addition, the book explores green infrastructure as the future of storm water management, and introduces techniques that can help reduce the thermal impacts of storm water management practices. Based on the author's more than thirty years of experience, this book includes numerous examples and case studies illustrating the methods and procedures needed to design, maintain, and understand structural and nonstructural storm water management systems. It covers every component of the storm water runoff process, discusses commonly employed runoff models in the United States, and introduces a physically based model developed by the author.
The urban wastewater and storm management has a long history which coincides with the appearance of the first organized human settlements ( ca . 3,500 BC). It begun in prehistoric Crete during the Early Bronze Ages ( ca . 3,200 BC) when many remarkable developments occurred in several stages known as Minoan civilization. One of its salient characteristics was the architecture and function of its hydraulic works and especially the drainage and sewerage systems and other sanitary infrastructures in the Minoan palaces and other settlements. These technologies, though they do not give a complete picture of wastewater and storm water technologies in ancient Greece, indicate that such technologies have been used in Greece since the Minoan times. Minoan sanitary technologies were transferred to Greek mainland in the subsequent phases of Greek civilizations, i.e. in the Mycenaean, Classical, Hellenistic, Roman, and present times. The scope of this article is the presentation and discussion of the evolution of waste- and storm-water management through the long history of Greece focusing on hydraulic characteristics of sanitary infrastructures. Also, the present and future trends of wastewater and storm water management are considered. Practices achieved in prehistoric Greece may have some relevance for wastewater engineering even in modern times.
The seasonality of the hydrometeorologic characteristics of floods that occurred in Crete during the period 1990–2007 is presented. Hydrological characteristics were analyzed using seasonality indices based on a dataset of 53 daily precipitation stations as well as 15 daily and 7 monthly recording flow stations. The atmospheric circulation conditions during the flood events were examined based on a joint subjective classification and meteorological analysis. The flood event-based seasonality was found to coincide with the seasonality of the daily precipitation maxima of November and December. The seasonality of the three largest long term daily precipitation maxima indicates that 50% of the maximum precipitation events occur from November to January (NDJ period). Analysis showed that the maximum annual stream flows in Crete are lagging by approximately 1 month from annual maximum daily precipitation in the region. The circulation type classification of the flood events showed that most of the weather systems occurring in the Mediterranean and passing over Crete have SW, NW and W direction. For the majority of the events, a common mean sea level pressure gradient field was observed over Europe. This comparison of the seasonality of selected hydrometeorologic characteristics reveals valuable information within the context of flood occurrence.
The ancient dam at Tiryns. Postgraduate thesis, Dept. of Water Resources, Hydraulic and Maritime Engineering
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Flood periods during prehistoric and historical times on the Kladeos River: Ancient Olympia
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Fountoulis, I., Mariolakos, H., Mavroulis, S., Ladas, I. (2008). Flood periods during prehistoric and
historical times on the Kladeos River: Ancient Olympia. Proc. of 8 th Intern. Hydrogeological
Congress of Greece (Eds: G. Migiros, G. Stamatis, G. Stournaras), pp. 809-818.
Water supply and use in the Roman city of Aptera, Hellas: The mystery of the ancient water system
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