Complex sentence: Culverts that offer adequate Aquatic Organism Passage by reducing impediments to movement of fish, wildlife and other aquatic life that require instream passage are less likely to fail in medium to large scale rain/snow melt events.
Split into simpler sentences: Culverts that offer adequate aquatic organism passage reduce impediments to movement of fish, wildlife and other aquatic life that require instream passage. These structures are less likely to fail in medium to large scale rain/snow melt events.