Developing a statistical model for locating bedrock shoal habitat to aid in understanding naturally occurring denitrification processes in a mid-sized river
Abstract
This research presents results from an ongoing study of denitrification in bedrock shoals of the Cahaba River of Alabama. Previous research suggests that plant macrophytes and their associated microbial communities located in bedrock shoals help reduce DIN concentrations by 50% in the Cahaba River. As a first step in creating a geo-ecological model capable of predicting the location of denitrification 'hotspots,' we have developed a statistical model capable of predicting the location of bedrock shoals. We characterized rock integrity (GSI - Geological Strength Index), streamflow relative to bedrock orientation (perpendicularity index), and channel confinement (channel width/valley width) at shoaled (n=100) and non-shoaled (n=70) sections of the Cahaba River using aerial photography, field data, and geologic maps in a GIS environment. We used these data to develop a binary logistic regression model, which suggested that the two most significant variables for predicting shoal occurrence were rock integrity (p=.000) and perpendicularity index (p=.001). The model correctly predicted whether a location was shoaled or not 92% of the time. When used to predict the status of non-studied sites (i.e., not a part of the model's derivation) the model performed reliably, giving all shoaled locations > 90% probability of being shoaled and assigning < 35% probability of being shoaled to all non-shoaled sites. Though only a first-step in a long process, these results are crucial to creating a geo-ecological model to identify denitrification 'hotspots,' as bedrock-shoals provide a spatially explicit feature through which spatial variability of plant macrophytes and their associated microbial communities can be modeled at a variety of spatial scales.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFMEP43A0836D
- Keywords:
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- 5419 PLANETARY SCIENCES: SOLID SURFACE PLANETS Hydrology and fluvial processes;
- 0414 BIOGEOSCIENCES Biogeochemical cycles;
- processes;
- and modeling;
- 1825 HYDROLOGY Geomorphology: fluvial;
- 1625 GLOBAL CHANGE Geomorphology and weathering