9 Deforestation and Frequency of Floods in Romania
295
Analyzing the effects of the 1975 and 1979 floods in the Arges , river basin, it is
clear that the flood of 1975 (generated by a uniform rain on the basin) is the most
important, totalizing on the Arges and Sabar rivers a flooded area of 50.850 ha.
This hydrographic area is now highly regulated (having numerous dams, protective
dikes, adduction channels, etc.) being hydrologically controlled for the most part. The
problems generated here by the deforested surfaces are the generation of alluviums
that contribute to the clogging of the accumulation lakes, thereby diminishing the
flood-mitigation ability.
The main floods recorded on the Buzau River in the past years are 1969, 1971,
1975, 1980, 1984, 1991, 2005, and occurred either in May or in July. The flood of May
2005 affected the lower part of the basin (downstream of M˘ agura), respectively the
upper course, the area of Întorsura Buz˘ aului. The upstream area of the basin records
some periodical local floods at the end of winter, especially when the melting of the
ice causes the separation of some pieces of ice, that cause a blockage. The largest
floods were recorded at the M˘ agura hydropower station (1948, 1975—the maximum
flow of 2100 m
3 /s, 1971, 1969, 1980, 1984), that took place before the construction
of the Siriu dam (1994). However, the dam does not protect the downstream floods
caused by the tributaries of the Buzau River, as happened in July 2004 at Nehoiu,
where the tributaries of Buz˘ au (Bâsca Rozilei, Nehoiu) flooded the lower part of the
locality. In the Ialomit , a basin, the strongest floods (2001, 2005), were recorded on
the Ialomit , a, Prahova and Teleajen rivers, but also on the tributaries of these rivers.
Here, there were abundant precipitations, with increases in flows on the watercourses,
reaching and exceeding the defenses on some rivers.
On the Siret river, in the county of Br˘ aila, precipitation ranging from 22 to
130.7 l/m
2 , was recorded in 2005 and the flood was caused by the destruction of
the defense infrastructure. Among the most known floods produced in this hydrographic area are the ones from 1994, 1999, 2001, 2005.
In the last 100 years, the Olt river basin was affected by significant floods in the
years 1923, 1924, 1930, 1932, 1948, 1955, 1970, 1972, 1975, 1991, 1998, 2000, 2007,
2014. Between 1930 and 1970, the largest floods in the Olt river basin occurred in
1932 (April) and 1948 (June). After 1970, the main floods occurred in: 1970 (May),
1971 (July), 1972 (October), 1973 (March), 1975 (July), 1991 (May-June-July) 2005
(May–July–August). The maximum flows recorded during the flood in 1975 were
on the Olt River of 2.134 m
3 /s in Râmnicu Vâlcea and 2570 m
3 /s in Stoene¸ sti.
By comparison, in 1991, during the periods 26 May–5 June and 2–7 July, on the
Lower Olt, at all hydrometric stations, maximum flows were recorded with the probability of exceeding of 5% (Q max at Izbiceni = 2542 m
3 /s), smoothly transiting, as
the lower Olt storage lakes, which function as dams, are rated at maximum insurance
rates of 1 and 0.1%. In the valleys of the lower Olt, in the counties of Vâlcea and
Olt, about 36.000 ha, 1700 households, 800 km of roads, 15 industrial facilities and
public institutions, 60 bridges were flooded. The duration of the flood waves was
between 2 and 15 days.
Because of the arrangement of the Jiu basin in the north-south direction and the
maximum width development of the basin in the upper third, the floods that occur in
the basin are concentrated on the middle course and attenuated in the lower course.
295
Analyzing the effects of the 1975 and 1979 floods in the Arges , river basin, it is
clear that the flood of 1975 (generated by a uniform rain on the basin) is the most
important, totalizing on the Arges and Sabar rivers a flooded area of 50.850 ha.
This hydrographic area is now highly regulated (having numerous dams, protective
dikes, adduction channels, etc.) being hydrologically controlled for the most part. The
problems generated here by the deforested surfaces are the generation of alluviums
that contribute to the clogging of the accumulation lakes, thereby diminishing the
flood-mitigation ability.
The main floods recorded on the Buzau River in the past years are 1969, 1971,
1975, 1980, 1984, 1991, 2005, and occurred either in May or in July. The flood of May
2005 affected the lower part of the basin (downstream of M˘ agura), respectively the
upper course, the area of Întorsura Buz˘ aului. The upstream area of the basin records
some periodical local floods at the end of winter, especially when the melting of the
ice causes the separation of some pieces of ice, that cause a blockage. The largest
floods were recorded at the M˘ agura hydropower station (1948, 1975—the maximum
flow of 2100 m
3 /s, 1971, 1969, 1980, 1984), that took place before the construction
of the Siriu dam (1994). However, the dam does not protect the downstream floods
caused by the tributaries of the Buzau River, as happened in July 2004 at Nehoiu,
where the tributaries of Buz˘ au (Bâsca Rozilei, Nehoiu) flooded the lower part of the
locality. In the Ialomit , a basin, the strongest floods (2001, 2005), were recorded on
the Ialomit , a, Prahova and Teleajen rivers, but also on the tributaries of these rivers.
Here, there were abundant precipitations, with increases in flows on the watercourses,
reaching and exceeding the defenses on some rivers.
On the Siret river, in the county of Br˘ aila, precipitation ranging from 22 to
130.7 l/m
2 , was recorded in 2005 and the flood was caused by the destruction of
the defense infrastructure. Among the most known floods produced in this hydrographic area are the ones from 1994, 1999, 2001, 2005.
In the last 100 years, the Olt river basin was affected by significant floods in the
years 1923, 1924, 1930, 1932, 1948, 1955, 1970, 1972, 1975, 1991, 1998, 2000, 2007,
2014. Between 1930 and 1970, the largest floods in the Olt river basin occurred in
1932 (April) and 1948 (June). After 1970, the main floods occurred in: 1970 (May),
1971 (July), 1972 (October), 1973 (March), 1975 (July), 1991 (May-June-July) 2005
(May–July–August). The maximum flows recorded during the flood in 1975 were
on the Olt River of 2.134 m
3 /s in Râmnicu Vâlcea and 2570 m
3 /s in Stoene¸ sti.
By comparison, in 1991, during the periods 26 May–5 June and 2–7 July, on the
Lower Olt, at all hydrometric stations, maximum flows were recorded with the probability of exceeding of 5% (Q max at Izbiceni = 2542 m
3 /s), smoothly transiting, as
the lower Olt storage lakes, which function as dams, are rated at maximum insurance
rates of 1 and 0.1%. In the valleys of the lower Olt, in the counties of Vâlcea and
Olt, about 36.000 ha, 1700 households, 800 km of roads, 15 industrial facilities and
public institutions, 60 bridges were flooded. The duration of the flood waves was
between 2 and 15 days.
Because of the arrangement of the Jiu basin in the north-south direction and the
maximum width development of the basin in the upper third, the floods that occur in
the basin are concentrated on the middle course and attenuated in the lower course.