PA Aquatic Resource Restoration Conference 2026: Past, Present and Future

Legacy sediment accumulation has elevated floodplains throughout the Mid-Atlantic region, impairing hydrologic connectivity, water quality, and ecosystem function. Restoration practices that remove legacy sediment and reconnect streams to their valley bottoms are increasingly implemented, yet their implications for carbon cycling and greenhouse gas emissions remain poorly constrained. We present results from a 2.3-mile restoration corridor along Little Conestoga Creek in Lancaster County, Pennsylvania, where pre-restoration floodplains, restored floodplains, and newly created wetlands can be directly compared. Field measurements show that restored wetlands generally release less carbon dioxide than legacy sediment-impacted floodplains, while methane emissions increase, especially in depressional wetlands that remain saturated for long periods. In lab incubations, buried relict hydric soils exhibit low microbial activity under both aerobic and anaerobic conditions, suggesting minimal carbon loss during sediment removal or short-term exposure. Preliminary estimates indicate rapid soil carbon accumulation in restored floodplains. Together, these findings highlight both the benefits and trade-offs of floodplain restoration and underscore the importance of restoration design in maximizing carbon sequestration while minimizing methane emissions.