09-20-1982 Planning Packet - Laserfiche WebLink

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mpaa nnapa I "" MINNESOTA PLANNER August 1982 Vol. 3. Mo. 2 Wetlands Issue Hydrological Headache Prescription By Jim Bokor In the Twin CitiM Metropolitan Area, poorly corweived land manage ment techniques over the last several decades have rMulted in a number of serious drainage conflicts among communities sharing common water sheds. Corrective improvements for only 11 of the more serious problems have an aggregate price tag of more than *100 mOlion. It would be impossibie to accurately estimate the untold thousands of dolars spent on legal fees and salaries of personnel involved in ritersHy years of intsrcommunity negotiations often required to solve these problems. In sddhion to these 11 ••catas trophic" repair projects, there are some 100 smaller drainage problems rtcw exit ing in many of the metropolitan area communitiw. CoHectiveiy, these pro blems are expected to cost more than anothsr 1100 million to repair. While these drainage management problems motivated the State Legis lature and Metropolitan Council to enact and adopt new measures for better drainage control, neither body has yet gone far enough. A 1982 law now requires watershed planning in the Twin cities area, attd the Metropolitan Cound will provide plan ning guidance, but statewide Minne sota still lacks a cogent, modem, effective policy structure for seMirtg drainage disputes and preventing and settling conflicts in other areas of water resource management. Never theless, these measures constitute an important improvement in watershed policy by requiring planning which can lead to more thoughtful manage ment of drainage waters hy communi ties sharing common vwtershed bounce arias. A watershed is a tract of land whose perimeter is defii^ by an erratically circumferential ridge that is higher in elevation than any other part of the tract. Moat drainage •*rur»s off the surface of the land, flowirtg downward from the ridge throu^ a systsm of natural ••oorKluits,^' vegetated depres si ons, open channeb, marshes and wetlands, ultimately leav ing the watershed at the absolute lowest point, usually in a perennial stream. As drainage water flows through a watershed toward the outlet, much is held by vegetation or in upland depressions, and later evaporated, vwhile a small but crucial percentage is absorbed into the earth from where it is often later drawn for human water supply. Much is also passed along to ponds, marshes and wetlands before flowing into streams and major rivers. In a watershed whose original contours and vegetation have not been disturbed, all of the natural lattdscape features from the rim of the watershed to its outlet can be thought of as an intricate ••system.'^ all having evolved over geok>^ time r, a see-sawing balance. The surface of the land must be changed to accomodate a growing popuMon with its desires and needs . The question of how much growth a community should ertcourage or dis courage is largely a furtctlon of ecoTKMnic, geographic and political considarations related to the avaU- abOity of utility networks and proximity to major business districts. Those Conti:iiMd p§g9 2 Local Standards & Water Quality Robert D. Sykes, ASIA Among the greatest obstacles to good surface water marwgemern are requirements which have been a part of moat subifvision codes sinoe World War II. They include exces sive and inappropriate road standards, mHes of unnecessary sidewalks, and over-built storm sewers and storm drainage systems. All of these standards focus on the artificial and out-dated ••fast runoff approach to storm drainage. Although thb concept has been the startdrvd since the 19th century, its benefits are minimum and its costs maximum. It is also responsiWe for the increasing amounts of down stream flooding and erosion that plague our nation. By re-directing our subdivision re quirements to focus on a ••slow runoff^ concept, everyone benefits. Homes cost less to build. Towrrs save on long term maintertance and replacement costs. The environment benefits because more water is left on-site where it belongs, reducing downstream flooding and erosion. The benefits of natural drainage can be achieved through development standards that encourage slow runoff systems ar>d discourage fast runoff systems. The first step is simply to put a ••speed limit'^ on the rates of runoff which may be generated by new develoments. A good ••speed limif for runoff is that which takes place in nature: the runoff generated Continuad page 3