5.6.3 Other Issues
There are existing land-locked subwatershed units and basins within this subwatershed that the cities have been considering for outlet drainage projects. To protect the quality of downstream resources, local plans must either no longer consider this an option, or demonstrate how this could be achieved without impact to downstream water quantity or quality impacts. Outletting will generally be discouraged unless there is a demonstrated threat to property structures or public safety.
Modeled High Water Locations
The HHPLS identified a number of locations where modeling predicts that public roads, private roads, or private drives might overtop during infrequent events, or where there may be minimal freeboard above the flood level. Local plans should identify observed or these potential locations and assess whether the risk of occasional flooding is acceptable or should be addressed.
Flow Velocity or Erosion Issues
The HHPLS identified a number of locations where modeling predicts that under existing or future development conditions higher velocities than desired ay result in erosion at outlets or culverts, potentially warranting erosion control or energy dissipation. Local plans should identify observed or these potential locations, assess the need for such measures, and set forth a plan for preventing future erosion.