19 June 2001
2-2.5.2 Groins. Groins are structures designed to control the rate of shifting
is minimized. Groins project outward, perpendicular to the shoreline, and are
constructed of large rocks, pre-cast concrete units, reinforced or prestressed
concrete piles, steel sheet piles, or timber cribbing filled with rock. Figure 2-7 is
an example of a groin.
2-2.5.3 Jetties. Jetties are structures that extend from the shore into deeper
water to prevent the formation of sandbars and to direct and confine the flow of
water due to currents and tides. These structures are normally located at the
entrance to a harbor or a river estuary. Jetties are usually constructed of mounds
of large rubble about a meter above the high tide mark. Figure 2-8 shows the
position of jetties at a harbor entrance.
Figure 2-7 Groin