Integrated River Management - River Dynamics and Integrated River Management - page 719

development; and (3) protecting, restoring, or improving the natural river ecology and landscapes. Rivers
sustain ecological systems, which also have economic value, and in turn generate a healthy hydraulic
system. People are able under stress conditions to make cautious use of water, thus, not preventing the next
generation from having similar benefits from the same water system.
The necessity of integrated river management may be learned from the case studies for the Rhine,
Yongding and Mississippi rivers. The Rhine River is the largest river in Germany and the second largest
river in central and west Europe. In the past, the river changed its bed after each flood due to bed load
transportation. The floodplain had a width of up to 10 km. In 1817, Tulla initiated the channelization of
braided Alsatian section of the Rhine and his often quoted statement “As a rule, no stream or river needs
more than one bed!” became general policy for hydraulic engineers ( Gore and Petts, 1989 ). Tulla tried out
techniques of cutting of bends and fortifying shorelines through levees and shore protection measures.
Only when he convinced himself of the effectiveness of these measures did he set out to straighten the
Rhine River in the whole upper Rhine valley. The Rhine training project was completed in 1872. The
length of the river course was reduced by 23% and the channel was deepened and narrowed. Another
project was set up to increase the capacity of the river as a waterway by increasing the depth of the
navigable channel up to Strasbourg and Basel, and this was done under the leadership of Max Honsell
( Gore and Petts, 1989 ).
After the river bank was hardened, the flow resistance was reduced greatly and the flow velocity
increased. The time for the flood peak to pass from Basel to Karlsruhe was shortened from 64 hours to
23 hours. The Rhine flood peak then met with the flood peak from the Neckar River severely and
threatened the downstream area. The area of swampland and bottomland flooded during the flood season
decreased from 1,000 km 2 to 140 km 2 . The capacity of the flood control facilities in the downstream
reaches was reduced from guarding against a 200-year flood to a 50-year flood (Jiang, 1998). The channel
was scoured several meters owing to the high velocity. Some reaches were scoured up to 7 m during the
period 1860-1960. The lowering of ground water led to the deterioration of navigation channel, leaving
the abstraction works and harbor constructions useless, and endangered the river bank and constructions
along the river. To solve these problems engineers had to feed the Rhine with gravel at a high cost. Every
year 170-260 thousand tons of gravels are added to the river downstream of Iffezheim Dam (Kuhl, 1992).
The hardened banks also reduced the self-purification capacity of the Rhine and the increased flow
velocity impacted the ecosystem of the river. The pollution in the Rhine stood out with social and
economic development and the river ecology were deteriorated (Wang, 2002). The nations in the Rhine
River basin restored the river primarily with a huge investment in the past 50 years.
The similar problems occurred in the Danube River after a series of river training projects, including
meander cutoffs, bank hardening and dam construction. The regulated river channel is not as beautiful as
the natural one and the flood wave propagates too fast and overwhelms the flood defense system in the
downstream reaches. Many people have sought to renaturalize the Danube River.
The Mississippi River watershed, which drains 41% of the territory of the contiguous 48 states of the
U.S., has undergone massive transformations in the last 200 years (Milliman and Meade, 1983). The
main engineering projects were stepped dams and ship locks, which have increased the water depth for
navigation. The middle and lower reaches were channelized with hardened banks and numerous spur
dykes (Su and Wang, 1997; Hou and Xu, 2001). The bend cutoffs in the lower reach reduced the channel
length by 30% (Xu, 2007; Izzo, 2004). The sediment transportation has been reduced and less than one third
of the sediment carried by the river 100 years ago is transported to the estuary. As a consequence the
Mississippi Delta and the coast lost more than 4,920 km 2 of wetlands over the past century. Restoration
engineering has been proposed to stop the land loss and enable coastal Louisiana to become stable and
self-sustaining.