Vízügyi Közlemények, 1998 (80. évfolyam)

4. füzet - Petrőcz Bálint: Győr árvízvédelmének fejlesztése

Győr árvízvédelmének fejlesztése 599 the bricks of the neighbouring demolished old houses, which were similar to the large brick of which the fortress was made (Figure 4.). The left bank defence line of the River Mosoni-Danube expands from the village of Vének to the village of Dunaszentpál. Before the development the length of this dike was 33.7 km and was made mostly of earth. Within the inner city of Győr the flood defence structure was a flood-wall (Figure 5.), which have been upfilled after the flood of 1954. Strengthening of the left-bank defence-line of Mosoni Danube (Figure 1

.) was made, within the City limits, with various technical solutions: — Particulate matter was used for strengthening the off-river side of the levee (Figure 1.) — A mixed structure flood defence wall was made on the site of the fllled-up old defence-wall (Figure 5.). Flood safety is provided here, by a levee constructed to withstand the 1000 year flood and a reinforced concrete wall on the top of this levee (Figure 6. and 7.). — In the reach between the Kossuth bridge and the István Széchenyi High School the lining on the crest was made of V1ACOLOR. — Stairs and ramps were constructed for accessing the water at each street crossing and at the boathouses when the left-bank defence line of Mosoni-Danube was strengthened (Figure 9.). Reconstruction of the right-bank defence-line of the River Rába was made, on the section between Kettős Bridge (Double Bridge) and Petőfi Bridge, of reinforced concrete wall of the L shape (Figure 3.). Crossing of the defence line was facilitated by flood-gates for vehicles and pedestrians. Many technical problems had to be solved in the left-bank defence line of the River Rába and in the right-bank defence line of the River Rábca. The first difficulty was faced in the section between 0+315 r.km and the Kettős Hid. Here the only possible solution was to build a flood-defence wall in the narrow band of 15—22 m width which was available between the two-storey houses (Figure 1.). On the water side there was space to built a levee of the slope 1:2 with a crest width of 1.0 m only. On the other side a flood wall of 1.0 m height was constructed parallel with the buildings. On this site the cross-section area of the levee is not sufficient for withstanding seepage water and thus the a concrete foundation of 3.0 m depth was constructed for the flood-wall (Figure 3.). The old flood-wall between Kettős Bridge and Petőfi Bridge had to be removed and the new defence line (flood levee) was constructed along the banks of the Rába river branch. The next problem was faced at the section between Petőfi Bridge and Béke Bridge. In this reach the flood levee has steep slopes of 1:1.5—1:2 on the water side of the River Rába. A flood-wall of deep foundation had to be constructed here to provide sufficient stability. The right-bank defence-line of 2520 m length of the River Rábca (Figure 1.) joins the left-bank flood levee of the River Rába. The consruction plans have been prepared but the strengthening of the levee on both side was made until the Pinnyéd bridge only, because the flood defence system of Győr was modified in the mean time with the cutoff of the Püspökerdei section of the River Mosoni Danube and with the translocation of the mouth section of the River Rábca. The bottom width of the cutoff channel of Mosoni-Danube at Püspökerdő is 60 m. The upper width of the channel is 90 m with 1:3 bank-slope. The distance between the axis of the channel and the axis of the flood-levee is 125 m (Figure 11.). The cutoff is shown in Figure 12. The new mouth section of the River Rábca (the Rábca spillway) has 14.40 m bottom width. The width of the upper part of the channel is 33 m with slopes 1:3. The distance between the axis of the channel and the axis of the flood-levee is 80 m (Figure 11.). One of the advantages of this solution is that one of the most problematic river reaches (from the point of view of flood-defence and excess water drainage) was removed from the densely populated residential area of the City. Also the total length of the first order defence line was shortened by about 4 km and the old flood-defence structures became the second order defence scheme (Figure /.). A new structure was built in the new mouth section of the River Rábca to counteract the backwater effects of the River Danube (Figure 13.). The role of this new structure of 8.0 m width include: — It acts as a flood-gate, excluding the floods of the Mosoni Danube from the River Rábca.