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 !