Coping with Uncertainty: A Case Study in Sediment Transport and Nutrient Load Analysis

We present a computational approach for identifying the significance of uncertainty in assessing the consequences of sediment and nutrient transport in a section of the Chattahoochee River south of Lake Lanier, as it passes through Atlanta, Georgia. Specifically, our analysis aims at identifying the key control and management actions, and the key scientific uncertainties about the fluvial system, that govern the attainment of a set of water quality objectives for the downstream boundary of the study area. To this end, we present a computational framework that integrates a recently developed sediment-nutrient dynamics model with a Monte Carlo-based methodology for model uncertainty evaluation. Our results suggest that, in general, reliable execution of controls and management actions is more crucial to meeting the target values for flow, sediment, and phosphorus concentration, than the scientific uncertainties associated with fluvial processes within the river channel. We also discuss the potential utility of our framework for accommodating the various science- and policy-derived uncertainties in the total maximum daily load process.