This video features the main drainage channel constructed in The Colonies subdivision along Continental Parkway in the median. The channel was designed to keep storm sewer installation costs down and provide retention in larger rain events.  The channel contains a 24 inch pipe running down the center length of the channel. It collects runoff from nuisance water, minor storm events and flow from the surrounding Colonies storm sewer connected to it, including pipes larger than 24 inch.  The channel is 80 feet wide and has a compound cross section which includes a triangular section at the bottom and a trapezoidal top section.  It is designed to convey the 100 year storm event (1%).  The flowline of the channel contains a series of positive and negative sloped segments (sawtooth) in which area grate inlets are installed at the low points.  The inlets also act as an intersection point for the surrounding storm sewers to connect.  Long positive surface flowline runs are lined with concrete to prevent erosion. 

          When a storm event begins, the minor storm runoff will be conveyed to the inlets and into the 24 inch storm below the channel.  The 24 inch is also collecting any minor storm from the surrounding storm sewers connected to it.  As the storm intensity increases, the area inlets will begin to alternate between collecting inflow and allowing surrounding storm sewer flow to bubble up thru the inlets to the surface creating a “burping” effect.  As the inlets become inundated and can no longer handle the increased storm runoff, the stormwater runoff in the ditch will begin to collect in each basin created by the high points situated between the inlets.  The basins provide a retention area for the runoff to collect and rise until it breaches the next downstream high point in the channel flowline and flows downstream to the next area inlet.  As this process on the surface continues, the 24 inch storm below is flowing full downstream to the next inlet box. This action continues for each inlet as the flow proceeds downstream until it reaches the final area inlet box, which then ties into a storm sewer that outfalls into McDonald Lake. In the event that storm sewer has reached capacity, the entire channel is designed to act as a retention pond until the hydraulic grade line breaches a high point in Coulter Street and flows overland into the McDonald Lake.  Finally, the perimeter of the channel contains a lighted concrete hiking trail that allows ADA accessibility and pedestrian junction points at each street intersection, including a pedestrian bridge and benches.