09-20-1982 Planning Packet - Laserfiche WebLink

Home Browse Search

Hydrologic Headache (Continued) ^ ...______ .K- w-«te«hed bv homelots. dead leaves, grass a^ concerns are really separate from questions of how different uses w the land, which are agreed *o “ desireble, ought to be designed. Drain age “improvements" have long bow recognized as one of the first Infr^ structural changes to bo installed in lar>dscspes to be newly developed or intensely farmed. The 100 or so developmont-roWod drainage conflicts in 76 metropolitan area communities, however, suggest that more thoughtful designs w needed. In fact, it is increasingly obvious that despite plenty wisdom about how a new building should look and function, how h should be located relative to other buildings and how it should be ser viced vwth a network of ubiitlw and oven how its foundation should be corwtructed to properly bear w building's weight on the site's soils, one crucial consldaratlon b still often overlooked: the Integisl nature of the chosen site with the/ surroundi.»g terrain, artd the natural "Wrtetlc relationship the site has with Its surroundings. Intvsstingly. kinetic oonnectiom (the natural energy dynamics existing mong, in this case, the integral, if separately definaWo, systems of land and water) can tolerate considera^ physical disturbances before they be gin to rovorborato out of control. An excellent example of natural systems with dynamic parts that are kinetically related is the landscape and Its hydrology, or drainage system. The landscape is, in fact, one wholly integrated system of land and water features. It can be thought of as a kinetic (i.e.. energy interactive) system. Tharo ora significant dliact and indirect monetary advantaf^ to be realized from maintaining Wnetic en ergy balances of the earth's systems as the landscape is changed to meet physical devetopm wt nee^. Present day economic condWor» demartd tto we use our best technical skills, wisdom and thinking to minimize kinetic disruptions In our landscape systems or wie wrill continue to pay the consequences in hard cash that we don't have. Orre of the best ways rroT to minimize such dhruptione isto instafl extensive highly ertgineered systems of stonn sewers, which can efficientiy collect drainage water from a specific she. but upset the hydro- logic balance of the water^ed by increasing the volume and intensity of drainage water sped through pipes to lovirer reaches of the watershed. This short-circuiting of natural pat terns of flow causes downstream flooding, erosion and nonpoint source pollution. Stream banks we often the orthen features most seriously peer ed by erosion when they are forced to carry more water from frequwt storms than they vrere naturally de- sigrted to carry. A common cause of nonpoint source pollution is storm sewers which dis charge directly into lakes or streams, having collected water from large areas of now development or farmland. CUKuroBy generated, nonpoint source pollution really has two components. The first Is a huge array of organic and mineral substances (call them "residuals") which are intentionally placed on or "fall out" onto the surfaces of the landscape. The re siduals come from manufacturing, commerce, residential and recreations areas, the transportation network and farming. , The second component of nonj^ pollution is simply a mechanism which carries the re^uals directly to a lake, pond or stream. ___ Residuals, therefore, are only ^ tential" nonpoint poHutants until they are scrubbed into a drainage stream and transported to a receiving wrter. While hard-falling rain or rushing meltwster need rro assistance to pick up the residuals, extensive netwo^ of stnrm sewer dreinage pipe proviw urtintemjpted uansportaion for the pollutanu to the surface watw. Drainage tiles beneath farmland have the same effect. Over time, common nonpoint pollutants, such as elements of fertilizer (which come not only from farms, but also from homelots. dead leaves, grass and other vegetation), accumulate inthe bottom serfiments of takes and pondsi When lakes naturally turn over every year, the accumulate fertilizers Imteirabie algae "blooms." New load ings coming into the water each ywr add to existing loadktgs, also recycling annually. Eventually, algae blooms. In addition to other aesthetic nuisances, can kill desirsbie forms of fish that require high oxygen cortcentraiions for survival. Waters degraded in this way can cost thousands of dollars per acre to reclaim. Loft to doclirto, a water which diminishes aesthetically also diminishes both the market and tax able value of real properties whw original value was associated dlrecfly or indirectly with the water. Since forests, fields, moedoi^. marshes and wetlands serve as highly efficient fihers, they can help mainta|n high quality drainage waters, even in fully developed or farmed areas. Watershed knbetanco ptobtarm, ty- mg corwoquonceo Bko those described above, alirwet always occur over tinw, as many small chartges—each with storm sowers that will load more drainage water at a faster rate to lower features of the vrotaished which did not evolve to, and cannot, cany the increased airrounts-are made In disparate kjcatiorte of the watershed. The effects of the changes on the hydrology of the watershed may not be noticed until a 10 or 20 year sir, m, firrally comes alottg. Major Cj^^Jy retrofitting Is then usually re quired to solve the problem. Extensive stripping, filling and grad ing the landscape for new physical prefect is very expensive In economic terms. It costs much more ihw natural "system seniltive development' techniques which integrate r»ew physi cal projects into the existing land scape uting the natural fearores of the terrain as furtctional design ele ments of the new project. Using the natural terrain to manage drainage is a prime example of this design philosophy. It can save sub- stmtially in initial construction attd ongoing maintenance costs to the community; and results in aestheti cally diverse and ecologically stable, affordable finished development. Th« author It Involved In Ir-*— rMMirch 00 puWie poiky onohnit