FishXing reports the following barriers to fish passage:

Barriers are calculated based on the following decision processes:

Velocity, Exhausted Burst, and Long

For each node in the culvert:

1) If the reduced average water velocity, (average velocity * velocity reduction factor) is greater than or equal to fish's burst speed then the culvert is a VELOCITY barrier at this node. If not:

2) If the difference between the fish’s prolonged speed and the reduced average water velocity, (average velocity * velocity reduction factor) is less than 0.01 ft/sec then the fish is not making adequate headway in prolonged mode and therefore swims through this node at BURST speed. If not:

3) The fish swims through this node in prolonged mode.

4) If the total time that the fish swims at prolonged speed exceeds the fish’s prolonged time to exhaustion then FishXing checks to see if the fish will make it through the remainder of the culvert at burst speed before reaching its burst time to exhaustion. If so fish swims through the node at burst speed.

5) If not, the culvert is a BARRIER because it is TOO LONG (the fish is exhausted in prolonged mode).

6) If the total time that the fish swims at burst speed exceeds the fish’s burst time to exhaustion the culvert is a BARRIER because the fish is EXHAUSTED in BURST mode.

Leap

If The Speed the fish must leap out of the water to successfully enter the culvert outlet is greater than its leaping ability as defined by the Max Leap Speed, a leap barrier is identified.

Drop

If the Outlet Drop (difference in elevation between the water surface at the culvert outlet and the tailwater) is greater than the  Max Outlet Drop, as defined on the Crossing Input Window  the culvert is a barrier at that flow due to the an excessive outlet DROP.

Depth

If the water depth anywhere  in the culvert is less than the Minimum Depth as defined on the Crossing Input Window a DEPTH barrier exists at that flow. Generally the minimum depth is defined as the depth of water required to submerge the fish, see Fish Swimming more information. FishXing will notify the user of the total distance within the culvert that the depth is insufficient.

Pool

If the Outlet Pool Depth (Tailwater Elevation - Pool Bottom Elevation) is less than the Length of Fish as defined on the input screen, then it is considered to SHALLOW for leaping and is classified as a POOL barrier. This barrier criterion only applies to culverts with an outlet that requires leaping, see Fish Leaping for more info.

None

Indicates that none of the fish passage criteria was violated. The None barrier code indicates that fish passage was successful at the crossing for the given conditions and flow.