Modelling the effect of Flood Retention Ponds in Arachthos River (Arta, Greece)

<p>Arachthos River is the largest river in Epirus and the 8<sup>th</sup> largest in Greece; it is 110 km long and its drainage area is 2209 km2. After emanating from Pindus mountains (near Metsovo), it enters into the Pournari Reservoir in Arta, passes through Arta and discharges into the Ambracian Gulf near Kommeno. Arachthos River prevents flooding of the city of Arta and supplies water to most of Epirus.</p><p>The design of flood protection works in Arachthos River is currently in progress; it is performed by a consortium of Greek Consulting Firms for the Ministry of Infrastructure and Transportation. In the present work, we examine the effect of Flood Retention Ponds on the inundation area and the subsequent flood risk for the city of Arta. The Flood Retention Ponds are constructed immediately downstream of the Pournari Reservoir and 5600 m upstream of the historic Bridge of Arta; their exact locations were identified after a preliminary study and field surveys. Firstly, we performed the design of the Flood Retention Ponds, based on international standards and specifications found in the international literature; then, we performed hydrodynamic calculations using the Hydrologic Engineering Center's-River Analysis System (HEC-RAS) 1D/2D with and without the Flood Retention Ponds. Thirdly, we compared the calculations and the corresponding inundation areas and derive conclusions on the effect of Flood Retention Ponds.</p><p> </p><p> </p>

Waterscape and Floods Management of Greek Selinus: The Cottone River Valley

This paper investigates water bodies in the Greek colony of Selinus, Western Sicily-Italy. It focuses especially on one of the two rivers of the city: the Cottone. The investigative strategy adopted in this study consists of an interdisciplinary approach based on the analysis of archaeological evidence, Earth Sciences data, and the study of historical cartography. Results indicate that the Cottone River was not a swampy and unhealthy intermittent stream as it was believed so far; it was instead a fully functional water body featuring an active floodplain. Most importantly, research presented in this article indicates several floods occurred in Selinus from the second or third quarter of the sixth century BC to the end of the fifth century BC. These floods, which occurred at the peak of Selinus’ cultural and economic life, were related to severe major events, rather than seasonal floods, as suggested by other scholars. The management of these floods and the waterscape was crucial to the city’s prosperity. This article also analyzes the relationship between the Cottone River and the fortification walls located at the Cottone River Valley. Results indicate that the fortification walls functioned not only as a defensive infrastructure, but also as a hydraulic engineering solution for flood retention. A better understanding of the environment in which Selinus was settled is now available, and knowledge on the importance of waterscapes and their management has been enhanced.

Possible impacts of a hydropower reservoir on the flood hazard of an Alpine valley

<p>High mountain ranges are characterised by steep slopes and high precipitation rates, making Alpine catchments prone to frequent flood events. Fast runoff during heavy rainfall events, sometimes in combination with snow melt events, can cause severe damages in residential areas. Flood retention mainly depends on retention properties of the headwater catchment area and its interaction with the occurring flood regime. However, due to their special characteristics, Alpine catchments are ideal candidates for storage power plants as well. Currently, around 70 storage power plants are operating in Austria. Their large artificial reservoirs alter the flood retention properties in the upper catchment by potentially providing a higher flood peak attenuation, which of course depends on the available storage volume at the time of flooding. Since it already has been reported that climate change driven processes will increase flood intensity and frequency in Austria, it is of particular interest to understand how hydropower reservoirs alter flood dynamics and if they systematically could be used for flood retention in the future.</p><p>In this study the influence of a storage power plant on flood dynamics is shown for an example in the central Austrian Alps. The chain of analysed reservoirs is situated in the headwaters of the river Salzach, a Danube tributary. Based on observed runoff, the retention potential is analysed by comparing the possible natural flood event and the retained flood event in the catchment influenced by the storage power plant. Then its possible impact on the flood hazard downstream is investigated until the tributary drains into the Danube. </p><p>This contribution is part of the interdisciplinary research project “Policy Coordination in Flood Risk Management” (PoCo-FLOOD), which is funded by the Earth System Sciences program of the Austrian Academy of Sciences.</p>

COST Action LAND4FLOOD - Natural Flood Retention on Private Land: Overview of recent activities and future plans

<p>Every devastating large flood usually leads to initiation of different flood risk reduction activities. There are numerous options available how to approach flood risk management. Only limited part of approaches considered land management as significant topic in the flood risk management. Therefore, efficient and effective land management for flood retention and resilience is needed. COST action LAND4FLOOD (CA 16209) deals with natural flood retention on private land. More information about the specific cost action can be found on the web-page http://www.land4flood.eu/ and LAND4FLOOD twitter account @Land4Flood.</p><p>Some of the recent activates of the COST action include:</p><p>-Organization of series of workshops on different topics such as “Strategies for achieving flood resilience”, “Delivering Nature-Based Solutions (NBS)”, “NBS for flood retention in Southern Europe”, “Compensation Mechanism for Flood Storage”, “Innovative and successfully implemented strategies for achieving resilience in Flood Risk Management with a special focus on private and public property flood resilience” and organization of stakeholders meetings.</p><p>-Publication of policy briefs entitled “How Private Land Matters in Flood Risk Management?” that is also translated in French and Spanish and “Compensation for Flood Storage” that is available in Portuguese, Spanish, Czech and French versions.</p><p>-Support of multiple Short Term Scientific Missions (STSM) and ITC and conference grants.</p><p>-Publication of book about “Nature-based Flood Risk Management on Private Land” and multiple scientific papers.</p><p>-Preparation of the LAND4FLOOD leaflet (i.e. http://www.land4flood.eu/wp-content/uploads/2019/10/Leaflet-LAND4FLOOD-final.pdf) that is translated into Albanian, Bulgarian, Slovakian and Slovenian languages.</p><p>Moreover, the COST action will finish in September 2021, thus there are still several ongoing projects such as open STSM calls, workshop initiations, research project application and book proposals. For example, a recent book proposal that has just been launched will review what we know about flooding land and how to implement spatial flood risk management and resilience. More specifically, as pointed out land is needed for flood risk management. Thus, to store excess water and retain it without major damage. However, this land is often in private ownership. This book proposal will explore different options regarding storage of water in the catchment during flood events: in the hinterland with decentral measures, along the rivers in polders, washlands and in resilient cities. The book will put the focus on land as a biophysical system (including hydrological aspects), as a socio-economic resource, and as a possible solution for flood risk reduction (i.e. asking for policy interventions to activate the land for flood protection measures). These three areas (i.e. hinterland, along the streams, in resilient cities) and the three analytical lenses (i.e. processes to influence stakeholders and interests in land, socio-economic context of land and environmental conditions of land for retention) will indicate how to use land to reduce the impact of flooding.</p>