Assessing The Effects Of Streamflow Changes And Local Shear Stress Variations On The New Zealand Mud Snail In Boulder Creek, Colorado
Wynne, Kristina 1 ; Pitlick, John 2
1 University of Colorado, Department of Geography
2 University of Colorado, Department of Geography
In November, 2004, the invasive New Zealand mud snail (NZMS) was confirmed in Colorado. Previous studies of the NZMS in streams of the northern Rocky Mountains have provided some insight to their distribution and habitat preferences, yet the link to geomorphology has remained largely unstudied.
This study investigates the relationship between sediment transport and the density of NZMS in Boulder Creek, CO. Field measurements were conducted in the summer of 2005 and a one-dimensional flow model has been used to obtain local boundary shear stresses within the study reach. The modeled flow velocities will be used to determine whether NZMS population densities are significantly affected by variations in sediment transport intensity and resulting substrate disturbance.
Initial results indicate that the NZMS population in Boulder Creek did not spread downstream with snow-melt induced high flows. Additionally, results show that the snails not only prefer to attach to a particular grain size but that they also maintain higher densities where the local shear stress to critical shear stress ratio is low. In other words, NZMS densities are lower where conditions for sediment transport are favorable (local shear stress/critical shear stress less than 1). These observations are important as city, county, and state agencies consider management strategies to control the NZMS in Boulder Creek.