Implementing the Requirements of the European Flood Directive: the Case of Ungauged and Poorly Gauged Watersheds

Abstract

In 2007, the European Floods Directive (FD) 2007/60/EC came into force, introducing a framework for the assessment and management of flood risks. According to Article 6 of the Directive, Member States shall prepare flood hazard maps and flood risk maps at a catchment level, covering the areas that could be flooded under different probability scenarios. The former maps include crucial information towards flood management, such as flood extent-water levels-flow velocity, that will form the base of the flood risk management plans. Based on these data, Member States shall set their objectives and prepare measures concerning their flood management plans. Hence, it is obvious that effective flood management requires reliable methods for the estimation of the flooded areas, such as precise estimation of the peak discharge. This is a hard task for hydrological engineering, taking into account that in the majority of small catchments, especially in Greece, there is a substantial lack of hydrological data. The present paper presents the effect of the uncertainty, derived from lack of data, on the estimation of the peak discharge based upon which the flooded areas will be identified. Towards this direction, a methodology of peak discharge estimation is presented in an ungauged small catchment followed by hydraulic calculations using HEC-RAS and HEC-GeoRAS software packages. The results demonstrate the great variability of the estimated flood extent and the effect of it on the decision-making of the proposed flood measures.

The centrality of engineering codes and risk-based design standards in climate adaptation strategies

“…For example, while new ISO standards are being formulated for flood risk assessment (Yunika et al, 2017), they are based on the experience and existing guidelines of national agencies such as the Dutch Rijkswaterstaat, the Corps of Engineers or Japan's Ministry of Land, Infrastructure and Transportation. A similar situation exists with the European Flood Directive of 2007, which set in motion a cascading suite of new rules, regulations, prescribed analytical procedures and design standards (Tsakiris, 2015;Yannopoulos et al, 2015).…”

An integrated approach of flash flood analysis in ungauged Mediterranean watersheds using post‐flood surveys and unmanned aerial vehicles

“…The flash flood of November 2019 was reconstructed using the rainfall‐runoff model of Soil Conservation Service‐Curve Number (SCS‐CN) (SCS 1972). SCS‐CN is a well‐known and widely applied hydrological model in many countries (Mitra, Wright, Abhisek, & Ghosh, 2015; Rezaei‐Sadr, 2017; Steenhuis, Winchell, Rossing, Zollweg, & Walters, 1995; Van Dijk, 2010; Verma, Verma, Mishra, Singh, & Jayaraj, 2017), as well as in Greece (Kaffas & Hrissanthou, 2014; Kastridis & Stathis, 2012; Kastridis & Stathis, 2020; Myronidis et al, 2009; Nalbantis & Lymperopoulos, 2012; Papaioannou et al, 2018; Soulis, 2018; Soulis, Ntoulas, Nektarios, & Kargas, 2017; Soulis, Valiantzas, Dercas, & Londra, 2009; Stathis, Sapountzis, & Myronidis, 2010; Yannopoulos, Eleftheriadou, Mpouri, & Giannopoulou, 2015). The CN is a dimensionless empirical parameter that estimates runoff and infiltration from rainfall excess, and ranges from 30 to 100, with the highest numbers to indicate high runoff potential.…”

Evaluation of Hydrological and Hydraulic Models Applied in Typical Mediterranean Ungauged Watersheds Using Post-Flash-Flood Measurements

“…The lag time was defined by calculating the difference between the time of the precipitation peak and the time of the observed peak discharge at the outlet point of the watershed. To estimate the hydrographs of the two rainfalls (October 2006 and February 2010) in the Vatonias watershed, the SCS-CN model was used, a well-known and widely applied model in many countries [29][30][31][32][33] and in Greece [22,[34][35][36][37][38][39][40][41][42][43]. The CN is a dimensionless empirical parameter for predicting runoff and infiltration from rainfall excess [39].…”