Drainage & Storm Water Systems Flashcards

What is the purpose of a storm water detention basin in a highway right-of-way?

Answer: To temporarily store runoff and reduce peak discharge rates

Detention basins temporarily store storm water to attenuate peak flows, releasing water at a controlled, lower rate to downstream channels.

During inspection of a roadside ditch, you notice the ditch lining has separated from the soil and is undermined. What condition does this indicate?

Answer: Piping or subsurface erosion beneath the ditch lining

Separation and undermining of ditch lining indicates subsurface piping or erosion where water has moved soil from beneath the lining.

What is a 'subdrain' and what is its primary function in highway drainage?

Answer: A perforated pipe or aggregate trench that removes subsurface water from pavement layers

A subdrain is a subsurface drainage system using perforated pipe or aggregate to intercept and remove groundwater or perched water from pavement base layers.

When inspecting a concrete pipe culvert joint, what defect is most critical to document and report immediately?

Answer: Joint separation with visible soil infiltration or exfiltration

Joint separation allowing soil migration indicates potential pipe collapse, embankment failure, or sinkhole formation, requiring immediate reporting.

What is the KDOT-required minimum slope for roadside ditches to ensure adequate self-cleaning velocity?

Answer: 0.3%

KDOT generally requires a minimum ditch slope of 0.3% to maintain sufficient flow velocity to prevent sediment deposition and promote self-cleaning.

What does 'tailwater depth' control in culvert outlet hydraulics?

Answer: Whether the outlet is submerged, affecting hydraulic performance

Tailwater depth at the outlet determines if the culvert operates under outlet control and whether the exit is submerged, reducing overall hydraulic efficiency.

Which erosion control practice is most appropriate for a freshly graded roadside ditch on a KDOT project before vegetation is established?

Answer: Applying temporary erosion control blankets or erosion control matting

Temporary erosion control blankets protect exposed soil from rainfall impact and surface flow until permanent vegetation becomes established.