Abstract
An increase in severe precipitation events of higher intensity are expected to occur in the southeastern Mediterranean due to intensification of the hydrological cycle caused by climate change. Results of the climate change model’s precipitation data for the period 1970–2100 show a decreasing trend of daily precipitation but of higher intensity. Post-flood field investigation from a severe rainfall event in a small ungauged basin located in northwest Crete produced a validated flow hydrograph, and in combination with two high-resolution digital elevation models (DEMs), were used in the 1D/2D HEC-RAS (Hydrologic Engineering Center’s River Analysis System model), in order to determine the flooded area extent. Lateral structures were designed along the stream’s overbanks, hydraulically connecting the 1D streamflow with the 2D flow areas behind levees. Manning’s roughness coefficient and the weir coefficient were the most crucial parameters in the estimation of floodplain extent. The combined 1D/2D hydraulic model provides more detailed results than the 1D model with regards to the floodplain extent at the peak outflow, maximum flood depths, and wave velocities. Furthermore, modeling with a DEM at 2 m spatial resolution showed more precise water depth output and inundated floodplains. Scenarios of increasing peak precipitation for the same event precipitation depth were used to identify the flood extent due to an increase in daily rainfall recorded by adjacent meteorological stations. These simulation results can be useful in flood risk mapping and informing civil protective measures in flood basin management, for an effective adaptation to increased flood risk caused by a changing climate.
Highlights
According to EEA [1], from 1998 to 2009, floods and storms were the most expensive natural hazards in Europe, with the overall losses adding up to about EUR 52 billion for floods and about EUR44 billion for storms
The objective of this study is to examine parameter uncertainties in combined 1D/2D hydraulic modeling concerning a case study in Crete, regarding the values of the Manning’s roughness coefficient n at the floodplains, as well as the weir coefficient of the connecting lateral structures between the
Due to the intensification of the hydrological cycle caused by a changing climate, either more severe precipitation events or events of higher hourly intensity are expected to occur in the area of interest
Summary
According to EEA [1], from 1998 to 2009, floods and storms were the most expensive natural hazards in Europe, with the overall losses adding up to about EUR 52 billion for floods and about EUR44 billion for storms. Flood extremes with return periods over 100 years are expected, on average, to double in frequency in Europe until 2035, with an additional increment up to the end of the century, according to an ensemble of EURO-CORDEX climate projections with RCP8.5 scenario [2]. Analysis in both space and time of significant flood events in Europe during 1985–2009 have indicated an incremental drift of occurred flooding, overtopping the inundation severity and magnitude due to changing climate as well as changes in terrain surface [3]. Input data, such as inundation maps and digital elevation models (DEMs), when combined with a GIS-based tool (Floodwater Depth Estimation Tool, FwDET), can generate flood
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