A VALIDATION STUDY OF THE NORTH CAROLINA RAPID FIELD-BASED RATING SYSTEM FOR DISCRIMINATING FLOW PERMANENCE CLASSES OF HEADWATER STREAMS IN AGRICULTURE BASINS IN SOUTHERN ILLINOIS

• Main Author: Lampo, Miles
• Format: Others
• Published: OpenSIUC 2015
• Subjects: agriculture; Clean Water Act; headwater; streams
• Online Access: https://opensiuc.lib.siu.edu/theses/1730; https://opensiuc.lib.siu.edu/cgi/viewcontent.cgi?article=2744&context=theses

Rapid field-based assessment methods for classifying stream permanence in headwater streams are needed to accurately inform regulatory decisions regarding which streams are protected under the Clean Water Act. In North Carolina, a rapid field-based assessment method for identification of intermittent and perennial streams has been developed. The North Carolina Method (NC method) uses 26 attributes divided into three categories geomorphology, hydrology, and biology to assess a particular study reach's flow permanence. In this method, the attribute scores for a given study reach are totaled and the sum of the score is used to rank the reach as ephemeral, intermittent, or perennial. The study objective were to (1) evaluate the NC method's ability to classify the flow permanence of agricultural, low order, study reaches in Southern Illinois and (2) create empirical models that predict flow permanence at a given stream location. The results of the study show the NC method successfully differentiated ephemeral from intermittent and perennial study reaches 100% of the time. However, there was lower fidelity in differentiating between intermittent and perennial study reaches and correctly determined flow permanence 82% of the time. In two of the cases where the NC method categorized the streams incorrectly, the score was on the threshold between intermittent and ephemeral. If these study reaches were categorized during a drier period they may have scored correctly. These results suggest the NC method would be a strong foundation for the development of a rapid field-based assessment protocol method for Illinois. Regression models were developed to predict NC method scores using a variety of hydrologic, geomorphic, and land-cover metrics. Two statistically significant models (>95% confidence interval) for estimating NC method stream permanence scores were developed using these physical parameters. One of the significant regression models developed used watershed area alone as a predictor of the NC method stream permanence scores. The second significant regression model employed bankfull width, upslope surface-water area, and upslope area of grass lands. These models explained 61% and 69% of the variance in the NC method stream-permanence scores, respectively. While the regression models develop here are not capable of explicitly modeling stream-permanence class with a high degree of accuracy, they are useful for guiding stream-permanence study-site selection.