Terrorism and Security Issues Facing the
Water Infrastructure Sector
http://www.fas.org/irp/crs/RS21026.pdf

Hydroelectric dams are attractive terrorist targets because of
the potential for dramatic effects of the destruction of a major dam, the potential for downstream
damage and casualties from flooding, and the potential for impacts on the overall electric power
grid from the loss of generating capacity. Disruption of the facility without inflicting actual damage can
be intended to interfere with facility operations and the overall operation of the interconnected
power grid.

http://info.publicintelligence.net/DHS-Dams-PI.pdf

Small earthen dams are a vulnerable target as they have less security and and are primarily privately owned. But attack on a small earthen dam on creates effects in a locl are unlikely to effect the power grid. Currently, there are nearly 80,000 dams in the national inventory, most of which are privately owned. Less than 3 percent of those dams are owned by the Federal Government.

U.S. DAMS: IS SECURITY SEEPING THROUGH THE CRACKS | Government Security content from American City & County

• Buffer Zone Protection Plans (BZPPs): BZPPs identify
and recommend security measures and local law
enforcement coordination for the area surrounding a
facility, making it more difficult for a potential attacker
to conduct surveillance or to plan or launch an attack on
Dams Sector facilities.
http://www.dhs.gov/xlibrary/assets/nipp_dams.pdf

TVA dams provide 6%, Corps of Engineers Dams 24% of the power genreated by hydroelectic dams.
http://viktorvoksanaev.narod.ru/DHS-Dams-CV.pdf