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Possibilities of local sediment management
Balázs Tóth
Bratislava 2013.
Gravel banks, gravel islands in the main channel are rare habitats.
shallow littoral zone
high velocity
gravel or sand bottom
no waves
Gymnocephalus schraetzer
Gobio albipinnatus Eudontomyzon mariae
Zingel zingel Zingel streber
Ciconia ciconia
Phalacrocorax carbo
Haematopus ostralegus
Charadrius dubius
Selmeczi Kovács Ádám
www.fotoska.hu
Haliaetus albicilla
Loss of gravelbanks and gravel islands are evident in the Hungarian section.
Dredging
Amou
nt: i
n 10
00 m
3
Gravel dredging from Danube between 1709 – 1811 rkm (1975-1994 years) 45-50 million m3
10 million m3 gravel was dredged between Nagymaros (1692 rkm) and Vác (1680 rkm) between 1970-77. Resupplement 10.000 m3/year (Fürt 2010.)
10 million
0
0,2
0,4
0,6
0,8
1
1,2
out in
Calculating 40 years of resupplement (without any sediment outflow from this section)
400.000
Bank filtration wells !
Hydropower
1780 Beginning of 1800
1870 „Present” map 1980
River morphology changes (Szabó 2006). Higher velocity results more sediment movement
1908 1970-80 2011 (suspended
matter)
1.
2.
Different succesional stages – different habitats
1st stage:gravel islands
No really visible succession for 38 years in some places
Complex hidraulical situation
Is it possible to change or create structures, that help the river developing stable gravel islands?
Chevron-groyn http://www.thehawkeye.com/
http://www.mvs.usace.army.mil/arec/basics_chevrons.html
Modelled morphological changes due to new groins
János Józsa 2012
János Józsa 2012
Goal:
Find concrete site(s) in the Hungarian Danube section, where structure development can be planned, in order to help the river creating shallow gravel habitats.
Previously 3 study sites agreed with Water Management Directorate - Sződliget, Göd, Makád.
Communication has to be careful:
Possible navigation approach: „Look! You have the tools to build new habitats, so I can destroy the old ones!”
Artificially generated habitats can result in better situation (e.g. better ecological potential), but it is not our final vision about the Danube. It can be used only for changing bad abiotic situation in regulated sections, but we still don’t have rights to destroy natural areas.
KÖSZÖNÖM A FIGYELMET ! Thank you for Your Attention !