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                                                               FLOOD CONTROL

                                    

                by Reason McLucus



The following was written during the major flooding in the nineties.  I am posting it  now without attempting to modify it or review what I wrote then.  I cannot quarantee that I still agree with all of the proposals, but it's not an issue I'm interested in dealing with right now.  I am posting it now because the recent flooding may cause an increased willingness of politicians  to  develop better flood control  measures.


The recent flooding along the Mississippi River and some its tributaries demonstrates the need to change the flood control system both upstream and downstream. Government cannot
prevent all flooding, but local, state, and federal governments can adopt changes capable of reducing the amount of flood water and controlling floods more effectively so that they don't
significantly damage property.

Flood experts explain concepts like 50-year floods or 100-year floods in terms of the probability of heavy rain falling. However, runoff rather than just the amount of rain determines the
degree of flooding.

Land use changes such as urban development and elimination of upstream wet lands have gradually increased the portion of rainfall running off the land into the Mississippi and its
tributaries. A 50-year rain today will produce more runoff than a similar rain would have produced 50 years ago. Recent rains would have produced some flooding this year without land
use changes, but the changes increased the level of flood waters.



Upstream flood control systems emphasize moving potential flood water from the area quickly. This approach works well for the short term flooding that results from one or two heavy
rains in a small area, but exacerbates downstream flooding during the type of weather pattern that caused the flooding in the upper Mississippi River basin. Rains falling on high waters
rushing from upstream can quickly raise the water above flood level in downstream areas.

Upstream changes in the flood control system should emphasize preventing any increase in storm runoffs entering the river system and where possible reducing or controlling existing storm
runoffs so that the water doesn't create a threat of downstream flooding. Downstream changes should emphasize controlling flood waters by diverting them from developed property or
by increasing the area rivers can use to carry excess water, such as by moving levees farther away from river beds.



The federal government should adopt a policy that prohibits development or other changes in upstream wetlands that would reduce their ability to hold water after rains. Repeated rains
can limit the value of wetlands, but any elimination of wetlands increases storm runoff. Increasing the size of wetlands, other than by eliminating artificial drainage systems, wouldn't be a
cost effective way to reduce flooding because wetlands often don't hold enough water and because wetlands normally contain water except during very dry periods.

Local governments should require developers to design their developments to significantly reduce or control potential storm runoffs that their developments would cause, especially runoffs
related to large parking lots. Control measures would at least need to temporarily hold runoffs during periods of heavy rains and release the water only after stream levels have dropped to
near normal levels. Developers will complain about increased costs, but they should assume such costs rather than force residents downstream to assume a higher risk of flood damage.

Commercial developers could reduce runoff from buildings and large parking lots by constructing underground catch basins that could be pumped out when the threat of flooding had
eased. Residential developers could dig a hole on each lot, fill it with rocks, cover it with soil, and slope the land so that much of the runoff would flow to the area of the hole. This
approach might increase the threat of water getting into basements in the development, but why should they have dry basements at the expense of causing someone downstream to have a
wet basement.

Development regulations could take the form of requiring that new developments not create any increased risk of flooding of other developed areas, including those far downstream. Such
regulations might take a form similar to that used by some cities to prevent new buildings taken as a group from reducing the amount of open space. For example, some cities have
regulations that limit the height of new buildings to 20 stories, but allow a developer wanting to construct a 30-story building to purchase the rights to the extra 10 stories from someone
who only wants to construct a 10-story building.

Flood control regulations could allow a developer to compensate for new storm runoff by reducing existing runoff from some other source. For example, a developer might pay to contour
area farms to cause any runoff to flow into a pond constructed by the developer. Farmers would be able to use pond water later to irrigate their crops during dry periods.

In rapidly developing areas, developers might combine their funds to pay for widening the stream or river that drains the area of their developments. Widening a river, by moving its banks
away from the normal water line, allows it to carry more runoff without raising the level of the water higher than it would otherwise have risen. A community wishing to encourage new
developments might widen the river in advance.

Periodically dredging smaller upstream rivers in urban areas, especially those that only carry large amounts of water during periods of heavy rains, would allow them to carry more water
reducing the risk of both local and downstream floods. Water flows down hill with a velocity that depends on the change in elevation from one point to another. Storm runoff carries dirt
and debris into rivers where it can raise the level of the river bed. As sand and dirt build up in a river the elevation of its bed increases causing flood water to flow downstream at a higher
velocity.

Reducing the elevation of the river bed would allow the river to hold more water during dry periods, for possible recreational use, and carry more water during wet periods. The increased
difference in elevation between the river bottom and city streets would allow faster drainage of storm runoff. The reduced relative difference in elevation between upstream and
downstream areas would reduce the threat of downstream flooding because water would flow downstream at a lower velocity.

State and federal governments should establish a "flood lease" program for farm land that would compensate farmers for allowing temporary use of their land to store flood waters. The
government would construct some type of levee around farm buildings if necessary to protect them from flood waters. This program could also apply to "wetland" areas that are
sometimes dry enough to be used for agriculture.

Compensation would include paying farmers for crops they have planted as well as crops they would be unable to plant because of the water. Government would absorb any costs
needed to return the land to usable condition and design the system to divert flood water onto farmland in a way that minimized damage to the land.

Developers could choose to pay a tax(during periods of flooding) into the flood lease program to cover the costs associated with the need to allow flood water to cover more land. In this
situation, government might use dams, pumps, or other means to divert river water to flood leased farm land.

In the short run floods prevent farmers from planting or harvesting crops. However, in the long run floods can benefit farms by depositing top soil. Floods have been responsible for the
richness of the soil in "river bottom land". Small dams used in the flood lease could also be used to maintain higher water levels in rivers to provide water for irrigation during dry periods.

The federal government should consider establishing a system of diversion canals in upstream areas to divert water from river basins with flood problems to drier basins. These canals
would generally connect streams that are close to each other, but which feed different rivers. The system should be able to shift water from stream to stream through several different river
basins possibly shifting water as far as from North Dakota to Texas.

This system wouldn't simply shift flood waters. The system would also shift upstream water away from overflowing reservoirs to reduce the need to release water into areas with flood
problems. The need to release excess water from flood control dams played a major role in the flooding in northeastern Kansas as well as increasing the flood problem along the Missouri
River.

Construction of a system of pipelines connecting major rivers and reservoirs between the Rockies and Appalachians would also allow shifting water away from flood areas. Pipelines
could move water over, or through, hills between nearby rivers.

Such a system of canals and pipelines in eastern Kansas and western Missouri could have transferred some of the flood water from west of Kansas City to the Arkansas River basin
which empties into the Mississippi in southern Arkansas. A similar system in Illinois could have diverted flood water from the upper Mississippi into the Ohio River basin or into one of the
tributaries to the Great Lakes.

The federal government should construct new flood control dams, preferably in hilly areas that are poorly suited for development or agricultural use to avoid the need to take people's
homes or farms. Hilly areas have much higher runoff rates than flat areas and thus contribute more to flooding. New dams wouldn't have to be large or hold water for long periods. Water
could be let out slowly as soon as water levels downstream had fallen to normal levels.

Government could use canals and dams to divert and store water in areas where it would be most likely to eventually replenish underground aquifers. One of the primary faults of current
flood control philosophies is the failure to recognize that what is considered excess water during periods of heavy rain could be stored to offset the impact of a subsequent drought.

Rain seldom falls at the same rate it is needed. We either get too much or too little. Designing the flood control system to retain "flood" water for later use or moving such water to areas of
drought would reduce the potential for water shortages. Manual desalinization of ocean water is very expensive. The planetary weather system performs this process for free.

The most important change downstream would involve giving Old Man River more room to "keep rolling along". Where possible government should move levees farther back from the
river, possibly moving them as much as half a mile or more. The land between the levee and the river could be set aside for recreation or used for agriculture during drier periods. Levees
might be constructed to protect only developed areas and divert flood water onto land covered by the flood lease program.

Rebuilding levees at their current locations, except in heavily developed areas, would be a waste of money because we already know levees at these locations can fail. New levees should
be built high enough and far enough away from the river so the volume of water associated with recent floods would have only risen halfway up the levee. Good engineers always attempt
to allow for a margin of error in new construction. Moving levees farther from the river would provide a better margin of error for dealing with future high water periods.

Government should condemn damaged buildings and land that would be inside the new levees and pay owners what their property was worth prior to the flooding. Owners of property in
areas where the levees held but required sand bags to keep the river inside might also be willing to sell under such terms. The recent flooding will reduce the market value of property near
rivers until people forget this year's flood.

Government should construct canals or pipelines to divert flood water around heavily developed areas where moving levees would be impractical.

Local governments should prohibit new development near levees to allow using bulldozers to widen levees when heavy flooding is possible. Engineers need to develop a sturdier design
for levees possibly using thick layers of non-biodegradable plastic within the levees to reduce passage of water through them.

Moving entire towns should only be done as a last resort. The cost of moving a town includes reestablishing its economy as well as moving its buildings and replacing streets, utilities, and
sewage treatment plants. In some cases a town's economy may be so strongly associated with its location that attempting to move the town would destroy its economy.

None of the above measures would totally prevent future floods by themselves. However, together they would reduce the potential for flooding and facilitate control of any flooding that
did occur. Even upstream measures that only reduced runoff by a few thousand cubic feet apiece would significantly reduce downstream flooding if used by enough different communities.

Floods differ from the other major Midwestern calamity, tornadoes. The latter hit at random and seldom strike the same location twice. Floods occur at irregular intervals, but they always
strike the same areas. Our technology can do nothing to prevent tornadoes, but we can do something to control flooding and reduce the damages it can cause.

Flood control measures can be expensive, but replacing flood losses can also be expensive. The economic benefits of using flood water would offset costs associated with some of the
above measures such as diversion canals and pipelines.

Since this was written there has been concern about declining water levels in the Great Lakes. Diverting water from the Mississippi River Basin northeast of St. Louis to streams emptying
into the Great Lakes could reverse this trend. Part of this diversion would directly involve flood waters. Shifting water when areas to the west are having excessive rain would also help
relieve flooding on the Mississippi even though the streams on the northeast would only carry normal levels of water.
 


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