Flooding and Erosion Recommendations in the Action Plan (link)
The mountain streams in the Ashokan Watershed are subject to a wide range of flood conditions – from annual high water associated with spring runoff to the less frequent and quite damaging floods that have occurred at anytime during the year. Inundation from flooding is a known problem for Phoenicia and in other low-lying developed properties throughout the watershed. The more common problem associated with flooding hazards is streambank erosion.
Stream erosion is a natural process, but when the stream erodes into road embankments and bridge abutments or developed property, this natural process needs to be addressed by appropriate management. In some places, deposition of the eroded sediment occurs in sections of stream with insufficient capacity to transport the sediment. When this occurs at stream crossings, bridge flood conveyance capacity is significantly diminished. In addition to the hazards of flooding and associated erosion, water quality is significantly impaired by the erosion and entrainment of fine sediment (silt and clay) leading to excessive turbidity.
The specific findings for each stream evaluated so far can be found in the three SMPs developed to date. In general, the following findings adapted from the Esopus Creek plan can be stated: