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<br /> <br />Figure 2-1 <br /> <br /> <br />Terrace ~ <br />FIDOdPlai~t <br /> <br />(Above) 1\l1ajor physiographic elements of a <br />typical watershed. (Below) Major elements <br />of the hydrological cycle. <br /> <br />Figure 2-2 <br /> <br />''^ <br />..1 2, <br />.,{ ~('\..~2 <br />) . c ) <br />.r . . <br />,~ <;. <br />r;'--,>~-/!-r. ~~..-: Precipitalion <br />--r;'c/.' <br />',1' <br />" <br /> <br /> <br />12 <br /> <br />". <br />~ <br /> <br />Water Resources <br />Floodplains serve as natural flood and erosion <br />control systems by providing temporary storage of <br />floodwaters, reducing the velocity of the water, and <br />minimizing the amount of sediment that can <br />accumulate dOvvTIstream. They can also help maintain <br />,vater quality by filtering nutrients and impurities <br />from storm runoff and by processing \vastes. The <br />frequency and duration of floods are reduced as the <br />water is slowed do\vn and given time to infiltrate the <br />ground and recharge aquifers. Vegetation in <br />floodplains plays a critical role in protecting surface- <br />water quality by filtering sediments and nutrients <br />that are destined for rivers and streams. Excessive <br />nutrients can upset the balance and gro\\'th of species <br />and reduce oxygen levels in \vater. Excessive <br />sediment can clog streams and rivers and have a <br />harmful effect on the food chain by disturbing the <br />living and breeding grounds of many species, <br />including fish, insects, and crustaceans. <br /> <br />~ <br />~ <br /> <br />;; <br />~ <br />, <br />t <br />" <br />~ <br />,~ <br />~ <br />~ <br />< <br />> <br />~ <br /> <br />Biological Resources <br />Floodplains contain diverse groups of plants and <br />animal species called ecological communities. These <br />species share the need for certain soils and levels of soil <br />moisture that are available in floodplains. vVet <br />meadmvs, bottomland hardwood forests, and riparian <br />shrub \vetlands are examples of such communities <br />(Protecting Floodplain Resources 1996, 7). Flooding <br />maintains the ecosystems by depositing sediments and <br />triggering chemical processes that plants and animals <br />need to survive. Floodplains also serve as breeding and <br />feeding grounds for aquatic species and birds, and <br />contain the habitats of rare and endangered species. <br />During the 1993 Midwest floods, the flooding <br />transported \vater to traditional spavvning areas that <br />existed prior to urbanization and agricultural <br />conversion, resulting in significant increases in fish <br />population (Protecting Floodplain Resources 1996,6). <br /> <br />Societal Resources <br />Floodplains are a benefit to society because of both <br />what can be extracted from them and the activities <br />that can take place in them. Nutrient-rich floodplain <br />soils are some of the most prime agricultural sites in <br />the country. Fishing and forestry also take place in <br />floodplains. A broad range of recreational <br />opportunities exists in floodplains. Urban green ways <br />and \vildlife refuges are t\.vo examples. <br /> <br />~ <br />~ <br /> <br />THE IMP ACTS OF DEVELOPMENT <br />ON FLOODPLAINS <br />Flooding is not a disaster until people put themselves <br />and objects of value in the path of natural processes that <br />are taking place. Most development and human <br />disturbance of floodplains inhibits the ability of the <br />floodplain to perform its vital functions. For example, <br />vegetation and soils play crucial roles in maintaining <br />water quality and retarding runoff. Their disturbance or <br />removal when land is developed can inhibit or <br />eliminate the functions that the floodplains perform. <br />And the effect is cumulative. The more disruption that <br />takes place, the greater the elimination of the natural <br /> <br />~ <br />-I <br /> <br />1 <br /> <br />r <br />~ <br /> <br />, <br />~ <br />< <br />;> <br /> <br />i <br />> <br />