types of surveys, general and intensive, are needed to determine the
extent of forest damage from a storm.
are designed to determine geographical area affected by storms. These
are very quickly and easily done from the air. Using aerial survey techniques,
damaged areas may be sketched on preexisting maps or photographs, or
damaged areas may be aerially photographed. A planimeter or other device
is then used to determine acres affected.
are designed to collect information on volumes of timber damaged and
on conditions of surviving trees. Volumes of storm-damaged timber are
difficult to estimate with aerial survey techniques because damaged
trees are broken and twisted together. It is also difficult to determine
tree condition from the air. Consequently, intensive surveys usually
require ground-based plots for acceptable accuracy. The number and size
of plots are determined by desired accuracy, and by time and personnel
Tornado damage surveys
are unique because the storm tracks are usually long and narrow with
few surviving trees. Volumes of tornado damaged timber may be estimated
by taking systematic plots on a transect parallel to the storm track
but just outside the damage area.