Aquatic Barrier Inventory & Prioritization Tool

Aquatic Barrier Tool

Network complexity

A barrier that has upstream tributaries of different size classes, such as small streams, small rivers, and large rivers, would contribute a more complex connected aquatic network if it was removed. In contrast, a barrier with fewer upstream tributaries may contribute few if any size classes to the network if removed. In general, a more complex network composed of a greater range of size classes is more likely to have a wide range of available habitat for a greater number of aquatic species.

No size classes gained

Barriers that do not contribute any additional size classes are less likely to contribute a wide range of aquatic habitat.

Several size classes gained

Barriers that have several size classes upstream are more likely to contribute a more complex network with a greater range of aquatic habitat for a greater variety of species.


  1. Stream and river reaches were assigned to size classes based on total drainage area:
    • Headwaters: < 10 km2
    • Creeks: ≥ 10 km2 and < 100 km2
    • Small rivers: ≥ 100 km2 and < 518 km2
    • Medium tributary rivers: ≥ 519 km2 and < 2,590 km2
    • Medium mainstem rivers: ≥ 2,590 km2 and < 10,000 km2
    • Large rivers: ≥ 10,000 km2 and < 25,000 km2
    • Great rivers: ≥ 25,000 km2
  2. Each barrier is assigned the total number of unique size classes in its upstream functional network.