Dams Sector Consequence-Based Top Screen Methodology

• Drainage Area (Square Miles): Area that drains to a particular point (in this case, the
dam) on a river or stream.
• Streambed Elevation (Feet): The elevation at the dam corresponding to the lowest point
in the original streambed.
• Design Water Elevation (Feet): Maximum attainable water surface elevation, including
flood surcharge.
• Maximum Operating Pool Elevation (Feet): The upper limit or top of active storage.
The reservoir elevation that would be attained when the reservoir is fully utilized for all
purposes, including flood control. It represents the highest elevation achieved in the
reservoir under normal operating conditions.
• Normal Pool Elevation (Feet): The reservoir elevation at the normal or conservation
storage level (excluding flood and surcharge storage).
• Minimum Operating Pool Elevation (Feet): The lower limit or bottom of active
storage. It represents the lowest elevation to which the reservoir is drawn down under
normal operating conditions.
• 1% Duration Exceedance Elevation (Feet): The reservoir elevation that is exceeded on
average 1% of the time on an annual basis (approximately 3-4 days per year). Note: This
is not the same as the 1% probability exceedance elevation which is commonly referred
to as the 100 year flood.
• Historical Maximum Pool Elevation (Feet): The highest elevation attained in the
reservoir since construction.
• Date of Maximum Pool Elevation (MM/DD/YYYY): The date on which the highest
maximum pool elevation occurred.
Navigation Locks
• Number of Locks: Number of existing navigation locks for the dam.
• Length of Locks (Feet): Length of the main lock chamber.
• Lock Width (Feet): Width of the main lock chamber.
State and Federal Agency(ies)
• State Regulatory Agency: Name of the primary state agency with regulatory or approval
authority over the dam.
• Permitting Authority: State regulatory organization has the authority to review and
approve plans and construction specifications to construct, enlarge, remove, and abandon
dams (from the Dam Safety Act of 2006). (Y/N)
• Inspection Authority: State regulatory organization has the authority to require or
perform the inspection, at least once every five years, of all dams and reservoirs that
Appendix B: Consequence-Based Top Screen Worksheets 25