Flooding on the Mississippi
Causes, effects, consequences & management.
Background:
The Mississippi river is situated in the USA and flows through ten states; Minnesota, Wisconsin, Iowa, Illinois, Missouri, Kentucky, Arkansas, Tennessee, Louisiana, Mississippi. In total the Mississippi river covers 3733km. The drainage basin conditions of this river vary from day to day. That is why this river is very unpredictable.
Causes of the 1993 flood:
- Starting as early as the fall of 1992, heavier-than-usual rain and melting snow saturated the soil with moisture. When seasonal rains and snowmelt came in spring 1993, the water ran off into streams because it could not soak into the ground. So streams were already swollen when a rain-producing weather system stalled over the Midwest in June 1993, and unusually heavy rains fell in many places — often twice the normal summer amount. The rains lasted through August.
- The waters overwhelmed the normal river channel, so serious flooding hit Illinois, Iowa, Minnesota, Missouri, and other states in the Missouri and upper Mississippi basins, an area 500 miles long and 200 miles wide.
- Urbanisation on the flood plain was also a major factor as grass and tress have been covered over and concrete and tarmac. Replacing a permeable surface with an impermeable one has many effects on the river. Movement (transfer) of water into the soil from the surface (infiltration) is reduced dramatically along with throughflow, whilst surface run off is increased. This is because when trees were on the flood plain they had four jobs which helped keep the possibility of flooding to it’s minimum