Geoscience Reference
In-Depth Information
Figure 4-13.
Rural results of 1997 southern Polish
l ooding. Buildings were destroyed, and i ne-grained
alluvial topsoil was stripped away down to a base of
cobble gravel. All inundated crops were declared a total
loss, uni t for human or animal consumption due to
contamination by raw sewage. Trees in fruit orchards
were killed by prolonged submergence; many cattle and
other livestock died. Village of Pilce next to the Nysa
River, southwestern Poland. Photo by J.S. Aber.
Figure 4-14.
Urban consequences of 1997 southern
Polish l ooding. The Nysa River inundated low-lying
sectors in the city of Kłodzko. There was heavy damage
to buildings, streets, vehicles, buried pipes, and other
infrastructure. Lower l oors of buildings were
submerged and were temporarily abandoned for human
occupation. The high water mark can be seen by the
whitish stain on building walls. Photo by J.S. Aber.
4-14). Fifty-i ve people died during l oods, and
many more suicides took place in the following
weeks. The Polish l oods of 1997 were an imme-
diate economic and personal catastrophe for
thousands of people in the affected regions and
led to permanent changes in l oodplain soils
and drainage. On the other hand, the damaged
areas were reconstructed with modern building
techniques and appropriate hydrologic designs
for l ood control and management of drainage
basins. In the long run, safer living conditions
and stronger economic activity will result.
Development of drainage basins for shipping,
agriculture, water resources, recreation, hydro-
power, and urban growth often leads to
increased frequency and larger magnitude of
l ooding. Flood water usually contains much
i ne sediment along with raw sewage, oil and
grease, insoluble compounds, animal carcasses,
insect eggs, weed seeds, l oating debris and
many other dangerous, undesirable, or toxic
materials that may be introduced into wetlands.
Erosion and deposition of sediment may cause
permanent changes in channel and basin
geomorphology.
Both rural and urban areas may experience
substantial damage, as l ooding in southern
Poland demonstrated in July 1997. Prolonged,
heavy rains were generated by a stalled weather
system that persisted for several weeks over the
region. Major l ooding took place on the Odra
and Vistula rivers and on many of their tributar-
ies. Flooding on many streams and rivers was
the greatest of the twentieth century, and l ood
recurrence intervals on various streams are esti-
mated in the 200- to 500-year range. More than
200 bridges were washed away. Homes, vehi-
cles, farms, and factories were completely
destroyed in several locations (Figs. 4-13 and
4.4 Hydrologic functions of streams
and wetlands
Rivers and streams serve two basic hydrologic
functions in the landscape
-
to remove excess
surface water and to carry away sediment. Wet-
lands also serve two basic hydrologic functions
-
to store excess surface water and to retain
sediment. Any human modii cations of stream
channels, wetland drainage or watershed condi-
tions inevitably lead to changes in the hydro-
logic and sedimentologic regimes. All types of
agricultural, transportation, industrial, and urban
development involve modii cations of or changes
