While researching environmental topics, I came across a new term – rip rap. While the name is new to me, the concept is not. In fact, I’ve seen such structures often but I didn’t know what it was called.
What is rip rap?
Rip rap refers to large, loose, angular rocky material that is placed along shorelines, steep slopes, bridge foundations, and other shoreline structures to prevent erosion.
Rip rap is known by a number of other names – rubble, rock armor, or shot rock.
Usually, modular concrete blocks or granite stones are used to construct rip raps.
The size of the rocks varies between 6 inches and 30 inches in diameter. The size to be used to create rip raps depends on the rate of flow of water and the steepness of the slope.
Erosion and scouring by water or ice is a common problem in the foundations of bridges and along the shoreline of water bodies. Thus, rip raps are mostly used in three places:
a) Along the outer bank of a river bend
b) Along the shoreline of a lake
c) Next to supports in waterways
d) Near bridges along embankments
Over time, erosion swallows up sandy beaches, reduces the value of waterfront properties, weakens the foundations of bridges, and destroys adjacent roadways.
Rip rap is placed over a filter material of fabric, gravel, or sand to prevent water from moving up through the rocks.
Types of rip raps
Rip raps may be of two types – graded and uniform.
a) Graded rip raps contain stones of varying sizes. This is the preferred type of rip rap because it forms a flexible, self-repairing barrier. It is also less expensive to install.
b) Uniform rip raps contains stones of the same size. It is rigid and cannot maintain its integrity if the stones are moved. It is more expensive to install than graded rip rap because it requires more hand or mechanical labor to place the stones in a more or less uniform pattern.
How long does rip rap last?
Properly maintained rip raps can last for 30-35 years. Annual inspections are required to keep rip raps from collapsing.
How does rip rap work?
Rip raps dissipate the energy of the waves, reducing the destruction caused on the shoreline. The gaps in the rocks break up the waves and absorb some of the energy.
Advantages of rip raps
Rip raps offer several benefits as a protective structure:
a) Prevent erosion by absorbing the energy of flowing water and acting as a barrier between the shore and the water
b) Long-lasting and durable when maintained properly and inspected annually for cracks and repairs
c) Eco-friendly as it allows plants and marine animals to thrive in its gaps
d) Easy to maintain because the rocks are packed together and not stuck to each other. Damaged rocks can be replaced without fuss.
Disadvantages of rip raps
Rip raps do present some problems:
a) Costlier to install than vegetated slopes
b) Increased erosion may be seen at the toe and ends of rip raps
c) Rip raps cannot offer the habitat enhancement that vegetative slopes can.