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<br />expensive, surface conveyance, is also the most visible thus must be formu- <br />lated carefully. The most frequently opposed storm drainage works are <br />canalization (channel improvement) where an existing natural channel that <br />performed satisfactorily under natural flow. conditions is totally inade- <br />quate where peak flow is expected to increase from 5 to 9 times. The <br />improvement consists of increasing the conveyance efficiency which in <br />turn requires that the channel be protected against erosion from the <br />increased velocities. The position of the opposition is that the natural <br />landscape, an environmental asset, is being destroyed and replaced with <br />an environmental liability (a rock or concrete lined chute). <br />The blue-green concept (15) has been used in joint storage-recreation <br />planning. The storage ponds are designed such that they are surrounded <br />by overflow areas that are treated as public open space or developed <br />for recreation during nonstorm times. The overflow area is used during <br />times of flood to temporarily store stormwater so that the resultant <br />flow can be safely conveyed by the downstream channel. There are a <br />number of technical problems associated with the proper design and <br />functioning of these areas, but the concept is worthy of intense study. <br />The options available upstream are controlled primarily by local <br />building codes and site development practices. The kinds of proposals that <br />have been proffered include modifying curb construction so that runoff is <br />detained, elimination of roof drains (those that discharge directly to <br />sewers), detaini.ng stormwater on roofs, in parking lots, etc., grading <br />individual lots so as to encourage infiltration, detaining stO""Nater and <br />planning for low maintenance channels and open space areas. Most of these <br /> <br />23 <br />