POSTER PRESENTER: http://tinyurl.com/2024WSC-Nieset CO-AUTHORS: Elizabeth Miernicki, Eric Janssen, and Scott Wiesbrook, Illinois Natural History Survey TITLE: Spatial strategies for wetland mitigation success: Insights from Illinois landscape analyses ABSTRACT: Illinois does not have statewide ‘wetland restoration potential’ mapping to aid in discerning suitable sites for wetland restoration. Topographic Wetness Index (TWI) analyses paired with existing datasets from state and federal agencies provide the foundation for typical wetland restoration potential mapping efforts. This study additionally utilized field-verified wetland data. We studied three HUC 8 watersheds (Des Plaines (IL and WI), Upper Mississippi River - Cahokia-Joachim (IL and MO), and Embarras (IL)). In TWI spatial analyses, there are differing algorithms and assumptions for how water is modeled to flow and accumulate in a landscape. Three algorithms—D8, Multiple Flow Direction (MFD) and D-Infinity (DINF)—informing flow direction and flow accumulation were investigated in the context of TWI analyses. It was determined that the MFD algorithm was the best fit to field-verified wetland data (n=960). The “threshold” TWI value was found to vary between watersheds. The mean wetland TWI values ranged from 6.5 – 10.2. Since TWI threshold values are used to eliminate large areas of respective landscape from site suitability and are often set at a state or regional level, this result indicates that finer scale investigations such as at the watershed level may be important in not over- or underestimating this metric in determining areas of suitability. Other selection factors such as drainage class, depth to water table, and hydric classification percentage were found to have varying prominence between watersheds. The next steps in the development of this ‘wetland restoration potential’ mapping project will incorporate these variations in watershed characteristics, but the exact method is yet to be determined. BIO: Julie Nieset is an assistant research scientist in wetland plant ecology with the Illinois Natural History Survey, Prairie Research Institute, University of Illinois at Urbana-Champaign.