Waterways and water bodies worldwide are impacted by anthropogenic litter (hereafter “litter”), generated from non-point source pollution. This study analyzes litter loads across land uses within three watersheds: Ballona Creek, Los Angeles River, and San Diego River. Using extensive litter collection data from small drainages (approximately 572 locations, from .05-8.5 hectares), we developed model parameters used in a numerical stormwater simulation model, PCSWMM, to simulate the buildup and subsequent washoff of litter from the land surface. To date, no study has used litter washoff data to develop these parameters and apply them on a regional scale. Reported litter washoff data from the small drainages was used to select a maximum buildup possible for each land use. We compared two different methods to determine litter accumulation rates, using a linear function and an exponential function. Washoff parameters were set so that the only washoff variable was the runoff rate. The parameters for the maximum buildup possible and the accumulation rate constant were used in PCSWMM models for Ballona Creek and the Los Angeles River. Simulated washoff loads were validated against reported data from Los Angeles County’s Baseline Trash Monitoring study. Simulated washoff loads were closer to observed data when using an exponential function to characterize litter accumulation rates. The average accumulation rate constants varied between land uses, ranging from .023 to .054 (1/day). Further simulations will be conducted to estimate litter washoff in the San Diego River watershed. Standardized buildup and washoff parameters need to be further developed in order to model litter loading on a larger or regional scale.
.jpg "Kian Bagheri, n/a (he/him/his) photo")
