A Laboratory Study of Streambed Stability in Bottomless Culverts

Traditional culvert designs, in many cases, have become habitat barriers to aquatic and terrestrial animals. In response, environmentally sensitive culvert designs have been developed that function as ecological bridges. Bottomless and buried invert culverts are examples of such designs and are commonly used for fish passage. Additional design guidance specific to streambed stability in buried-invert or bottomless culverts under high flow events is needed. This study investigated incipient motion conditions for three substrate materials in a 0.61-m (2-ft) diameter circular bottomless culvert in a laboratory setting. This paper discusses the experimental methods used to determine incipient motion conditions and an incipient motion prediction method based upon substrate size (d_m), which may be useful for determining stable stone diameters to be used as riprap in simulated streambeds through bottomless and buried-invert culverts.