8 Romanian Danube River Floodplain …
255
intensity of river processes varies a great deal over a year, depending on hydrological changes in the riverbed, from the lowest levels, when the processes are carried out
only within the limited range of the riverbed to the maximum, when the processes
extend over a surface much larger, including the floodplain [51–60].
The almost complete embankment of the Danube floodplain with in-submersible
dams affected both the hydro-geomorphological system and the local and regional
topo-climates, a phenomenon enhanced by the global climate changes. Due to the
elimination of the floodplain reedbeds, the nutrient retention capacity has been
exceeded since the 1970s, with Danube waters being affected by a strong eutrophication which has led to the reduction or loss of submerged macrophytes, the change
of the specific algal spectrum and the proliferation of competitive species in the conditions of excess of nutrients (green-blue algae). These phenomena affect trophic
cycles, leading to the decline of biodiversity through the disappearance of some
species, many of which are of high conservation or economic value. Also, the hydromorphological processes with implications in the size of the riverbed on which the
flow depends in good conditions have been affected by displacements of the Danube
stream [38–44, 61–66].
Another action, whose effects were not considered, consisted of the construction
of Iron Gates and the development of build-up lakes for electricity purpose. Their
presence led to the alteration of the flood regime and to the decrease of the quantity
of sediments transported by the Danube, due to the decanting of the waters, resulting
in major changes in the dynamics of the Black Sea Romanian coastline. Another
effect of the Iron Gates is the disruption of the migration routes for sturgeon and
shad species. The transformation of the downstream natural floodplain ecosystems
into anthropogenic ones, for economic purposes, has reduced their functions in terms
of ecological, economic, recreational, aesthetic and educational perspectives [1–5].
Embankment works carried out in the 1960s, along the 800 km of the Romanian bank, in order to obtain arable land, led to the disappearance of the floodplain
reedbeds as water filters and shallow waters, favorable breading, spawning, nesting
and feeding habitats for species, in general. At a larger scale, much later, the increase
of the nutrients amount, from the intensive agriculture and wastewater from riverine
settlements transported along the river are the effects of eutrophication of the downstream lakes and changes or decrease of the fish species composition and populations
[43, 44, 56, 67].
In the 40’s, the scientist Grigore Antipa has promoted the naturalistic concept of
extensive landscaping, predominantly fisheries on higher elevation terrain—which
impose the interrupted embankment of the Danube floodplain thus restricting the
embankment area to only 130,000 ha. The proposed hydrotechnical constructions
was submersible dams, so that once every 10 years (average), the flood-defended
lands can be flooded, and their usage to change in fishing and forestry [38–42].
This concept can influence the incapacity of the in-submersible dams to ensure a
definite defense of the land and the inevitable disasters that would result, exemplified
by the dyke breaches observed over time. Furthermore, changing the hydrological
equilibrium of the river, which, without the floodplain, would raise its level to floods
to such an extent that ports, riverine settlements would be flooded, the dikes would
255
intensity of river processes varies a great deal over a year, depending on hydrological changes in the riverbed, from the lowest levels, when the processes are carried out
only within the limited range of the riverbed to the maximum, when the processes
extend over a surface much larger, including the floodplain [51–60].
The almost complete embankment of the Danube floodplain with in-submersible
dams affected both the hydro-geomorphological system and the local and regional
topo-climates, a phenomenon enhanced by the global climate changes. Due to the
elimination of the floodplain reedbeds, the nutrient retention capacity has been
exceeded since the 1970s, with Danube waters being affected by a strong eutrophication which has led to the reduction or loss of submerged macrophytes, the change
of the specific algal spectrum and the proliferation of competitive species in the conditions of excess of nutrients (green-blue algae). These phenomena affect trophic
cycles, leading to the decline of biodiversity through the disappearance of some
species, many of which are of high conservation or economic value. Also, the hydromorphological processes with implications in the size of the riverbed on which the
flow depends in good conditions have been affected by displacements of the Danube
stream [38–44, 61–66].
Another action, whose effects were not considered, consisted of the construction
of Iron Gates and the development of build-up lakes for electricity purpose. Their
presence led to the alteration of the flood regime and to the decrease of the quantity
of sediments transported by the Danube, due to the decanting of the waters, resulting
in major changes in the dynamics of the Black Sea Romanian coastline. Another
effect of the Iron Gates is the disruption of the migration routes for sturgeon and
shad species. The transformation of the downstream natural floodplain ecosystems
into anthropogenic ones, for economic purposes, has reduced their functions in terms
of ecological, economic, recreational, aesthetic and educational perspectives [1–5].
Embankment works carried out in the 1960s, along the 800 km of the Romanian bank, in order to obtain arable land, led to the disappearance of the floodplain
reedbeds as water filters and shallow waters, favorable breading, spawning, nesting
and feeding habitats for species, in general. At a larger scale, much later, the increase
of the nutrients amount, from the intensive agriculture and wastewater from riverine
settlements transported along the river are the effects of eutrophication of the downstream lakes and changes or decrease of the fish species composition and populations
[43, 44, 56, 67].
In the 40’s, the scientist Grigore Antipa has promoted the naturalistic concept of
extensive landscaping, predominantly fisheries on higher elevation terrain—which
impose the interrupted embankment of the Danube floodplain thus restricting the
embankment area to only 130,000 ha. The proposed hydrotechnical constructions
was submersible dams, so that once every 10 years (average), the flood-defended
lands can be flooded, and their usage to change in fishing and forestry [38–42].
This concept can influence the incapacity of the in-submersible dams to ensure a
definite defense of the land and the inevitable disasters that would result, exemplified
by the dyke breaches observed over time. Furthermore, changing the hydrological
equilibrium of the river, which, without the floodplain, would raise its level to floods
to such an extent that ports, riverine settlements would be flooded, the dikes would