Modelling the effect of Flood Detention Ponds in Arachthos River in Arta, Greece Georgios RONTIRIS, Georgios MITSOPOULOS, Elpida PANAGIOTATOU, Anastasios STAMOU Laboratory of Applied Hydraulics, National Technical University of Athens, Greece

BACKGROUND METHODS RESULTS • Arachthos River is the largest river in Epirus • After a preliminary study and field surveys we • The calculated hydrographs immediately and the 8th largest in Greece; it is 110 km determined the location of the Flood upstream of the Historic Bridge of Arta with long and its drainage area is 2209 km2. Detention Pond (FDP) that is shown in Fig.2; and without the Flood Detention Pond are shown in Fig.3. • After emanating from Pindus mountains (near the FDP was positioned downstream of the Metsovo), it enters into the Pournari Reservoir Pournari Reservoir, at the right side of • Fig.3 depicts that the flood peak remains in Arta, passes through Arta and discharges Arachthos River, between the Ionia Odos practically the same and only a small into the Ambracian Gulf near Kommeno. Bridge and the BOOT Weir. The FDP is difference is observed in the case the Flood Arachthos River prevents flooding of the city delimited by the existing Arachthos Detention Pond that is constructed due to of Arta and supplies water to most of Epirus. embankment on its left side and by the storage. natural slope of Ionia Odos Highway on its • The design of flood protection works in right side. The FDP is located 2000 m Arachthos River is currently in progress; it is upstream of the Historic Bridge of Arta. performed by a consortium of Greek Consulting Firms for the Ministry of Infrastructure and Transportation. • One of the main objectives of the flood protection works is to protect the Historic Bridge of Arta, a stone bridge of great cultural significance; it has been rebuilt many times over the centuries, starting with Roman or perhaps older foundations; see Fig.1. Fig.2. Location of the Flood Detention Pond Fig.3: Calculated hydrographs immediately • Embankments were redesigned at the left upstream of the Historic Bridge of Arta with and side of the FDP. The bottom of the FDP was without the Flood Detention Pond excavated to maximize its volume that reached 4.38 million m3. CONCLUSIONS • The inflow structure is a Broad Crested Weir, placed 2 m above the river bottom; its length • The effect of the construction of a Flood is 15 m. The outflow structure is a sluice Detention Pond on the maximum flow rate gate, placed 3 m above the river bottom; its immediately upstream of the Historic Bridge length is 5 m, its height is 2 m. of Arta is minor; thus, the effect on the • We performed hydrodynamic calculations Fig.1: The Historic Bridge of Arta subsequent flood risk is also expected to be using the Hydrologic Engineering Center's- minor. River Analysis System HEC-RAS 1D/2D. RESEARCH QUESTION • Other means to protect the traditional Bridge • We used the Flow Hydrograph of the 100-year of Arta should be examined, such as river • What is the effect of the construction of a flood as input; see Fig.3. The horizontal part diversions. Flood Detention Pond on the maximum flow of the hydrograph is due to the design of rate immediately upstream of the Historic flood diversion works immediately Bridge of Arta and thus on the subsequent downstream of the Pournari Reservoir. flood risk?