Estimating Flow through Riprap

Flume studies were conducted in which riprap-protected embankments were subjected to overtopping flows to determine the average interstitial velocity of the through-flow. Velocity measurements were made in riprap having median stone sizes D50 ranging from 1.02 in. (2.6 cm) to 6.2 in. (15.8 cm) on embankment slopes of 1–20%. A tracer solution injection and recording system was developed to estimate the through-flow velocities. The average interstitial velocities for 19 flume tests were measured and reported. A predictive relationship was developed in which the average interstitial velocity was a function of the embankment slope and rock size D10. Flow measurements varied ±40% about the average velocity.