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Learn-Assess flows. A negative aspect of such diversions is the false sense -of security that may prevail in the protected areas along with a lack of awareness that the floodway actually exists. Several high flow diversions have been constructed along the Mississippi River. Excess water has also been temporarily diverted from the Great Salt Lake to an evaporation basin to prevent lakeshore flooding. Home Leaminl! Center Back Stormwater Management Stonnwater management is the removal of water that falls directly onto properties as opposed to flood water that flows onto the property from upstream sources or an ocean surge. Stonnwater networks have historically been constructed in urban and agricultural areas to remove these waters. Generally, the stonnwater system removes the excess rainfall over a period of days and the temporary ponding floods only low-lying buildings and roads. A significant problem occurs when an agricultural zone with an adequate stonnwater system is urbanized. Large areas are paved with roofs, roads, and parking, contributing to additional runoff. Often, shopping centers and other developments are placed on natural drainageways. The pre-existing stonnwater network becomes inadequate for its new urban use. Localized flooding then occurs. In an alternative approach often used in new developments today, runoff may be retained on the site, within a regional system, and total runoff within a watershed may be managed so that discharges from different units reach the main channel at different times to reduce peak flows downstream. Natural drainage systems may be used instead of concrete-lined channels or enclosed pipes. Many local ordinances now require a zero-increment runoff for new development, Page 16 of36