What is a Rip rap apron?

The most commonly used device for outlet protection is a riprap apron. They are constructed of riprap or grouted riprap at a zero grade for a distance that is related to the pipe’s Diameter or Rise. These aprons do not dissipate significant energy except through increased roughness for a short distance.

What is energy dissipator in hydrology?

Energy Dissipator means a structure or a shaped channel section with mechanical armoring placed at the outlet of pipes or conduits to receive and break down the energy from high velocity flow. Energy Dissipator means a non-erodible structure which reduces the velocity of concentrated flow to reduce its erosive effects.

What is outlet protection?

Outlet protection can be a channel lining, structure, or flow barrier designed to lower excessive flow velocities from pipes and culverts, prevent scour, and dissipate energy.

What is hec 14?

HEC-14 Hydraulic Design of Energy Dissipators for Culverts and Channels. The purpose of this circular is to provide design information for analyzing and mitigating energy dissipation problems at culvert outlets and in open channels. These provide a background and framework for anticipating dissipation problems.

What is D50 riprap?

D50 = riprap diameter in feet. Thickness: The minimum thickness of the riprap layer shall be 2.2 times the maximum stone diameter (for a D50 of 12” or smaller), but not less than 6 inches. For D50 specified greater than 12 inches, the riprap layer thickness shall be 2 times the D50.

What is outfall protection?

WHAT IS OUTFALL PROTECTION? A storm drain outfall is where a storm drain pipe or channel discharges stormwater runoff to a natural waterbody. There are thousands of these throughout the Prince George’s County. Increased urbanization and stormwater runoff can damage an outfall.

What are the energy Dissipaters?

A means by which the total energy of flowing water is reduced, such as rock splash pads, drop manholes, concrete stilling basins or baffles, and check dams. In stormwater design, an energy dissipater is usually a mechanism that reduces velocity prior to or at discharge from an outfall in order to prevent erosion.

What size is rip rap?

The most commonly used sizes of rip rap are Grade 1 (12”-18”) and Grade 2 (18”-24”). This product is easy to install and repair, has a natural appearance and does not harm the environment.

What is a rock outlet?

Rock Outlet Protection is installed where the energy at the outlets of culverts or chutes are sufficient to erode the receiving channel or area. This fact sheet does not apply to continuous rock linings of channels or streams.

What are baffle blocks?

Baffle blocks (or dentated sills) may be described as a number of normally identical elements arranged in one or several rows orientated perpendicular to the direction of flow. Whereas a sill generates an overflow of the main current, blocks force the water both between the obstacles and above it.

What size is d50 rip rap?

From Curve 22-5, it can be found that the riprap for d50 = 3.4″ and 4.52″ will both be stable on a 2.5:1 side slope. This design procedure applies to riprap protection of shorelines surrounding open bodies of water, such as lakes, bays, estuaries etc. against the erosive action of surface waves.