15 March 2001
DISTRESS 45, DEPRESSION
7.1. Description. Depressions are localized pavement surface areas having elevations slightly
lower than those of the surrounding pavement. In many instances, light depressions are not
noticeable until after a rain, when ponding water creates "birdbath" areas; but the depressions
can also be located without rain because of stains created by ponding water. Depressions can
be caused by settlement of the foundation soil or can be "built up" during construction.
Depressions cause roughness and, when filled with water of sufficient depth, can cause
hydroplaning of aircraft. Deduct curves for depression are shown in Figure 7.1.
7.2. Severity Levels.
7.2.1. L. Depression can be observed or located by stained areas, only slightly affects
pavement riding quality, and may cause hydroplaning potential on runways (see measurement
criteria below) (Figure 7.2.).
7.2.2. M. The depression can be observed, moderately affects pavement riding quality, and
causes hydroplaning potential on runways (see measurement criteria below) (Figures 7.3. and
7.2.3. H. The depression can be readily observed, severely affects pavement riding quality, and
causes definite hydroplaning potential (see measurement criteria below) (Figure 7.5.).
7.3. How to Measure. Depressions are measured in square feet (square meters) of surface
area. The maximum depth of the depression determines the level of severity. This depth can be
measured by placing a 10-feet (3-meters) straightedge across the depressed area and measuring