1. Floodplain Wetland and Channel Biogeochemical Relationships following Dam Removal on a Coastal Plain River Adam Riggsbee 1, Robert G. Wetzel 1, Martin W. Doyle 2 and Jason P. Julian 2 1 Department of Environmental Sciences and Engineering at UNC-Chapel Hill 2 Department of Geography at UNC-Chapel Hill

3. Today’s Talk The dam removal begins…The dam removal begins… –Fresh Data (4-28-05) –Dam dewatering releases stored wetland surface and ground waters into the adjacent channel Biogeochemical impactsBiogeochemical impacts –DOC –NO 3, NH 4 –PO 4

4. Little River Background 4 th order4 th order Edge of piedmont and coastal plainEdge of piedmont and coastal plain Neuse River BasinNeuse River Basin Matrix supported sand/gravelMatrix supported sand/gravel Floodplain wetlands are permanently inundated bottomland hardwood forests (impounded)Floodplain wetlands are permanently inundated bottomland hardwood forests (impounded) ~ 8km impoundment~ 8km impoundment

5. Little River, NC Dam FLOW

6. Impoundment Dewatering

7. April 25, 2005 Impoundment Dewatering April 28, 2005

8. June 06, 2005 Floodplain Succession July 13, 2005

10. Little River, NC Dam FLOW ISCO 1 ISCO 2

11. Dewatering Hydrology Event occurred near baseflow (1.87 m 3 /s)Event occurred near baseflow (1.87 m 3 /s) Q peak = 3.20 m 3 /sQ peak = 3.20 m 3 /s DurationDuration –13 h Dam Team sampled for 8 hDam Team sampled for 8 h –6 h during event

17. Preliminary Conclusions Minimal loadingMinimal loading Short durationShort duration TSS/Nutrient contributions negligible relative to other dam removal studiesTSS/Nutrient contributions negligible relative to other dam removal studies –Doyle, et al. 2003

18. Little River, NC Dam FLOW ISCO 1 ISCO 2

22. Wetland Surface H 2 O Dewatering Little impact on channel biogeochemistryLittle impact on channel biogeochemistry TSS contributions rapidly attenuatedTSS contributions rapidly attenuated What about wetland groundwater drainage?What about wetland groundwater drainage?

25. Ongoing Dewatering Research

26. Ongoing Research Floodplain wetland plant treatmentsFloodplain wetland plant treatments –Colonized –Uncolonized Plant biomassPlant biomass Fungal biomassFungal biomass Bacterial productivityBacterial productivity Interstitial [N, P, C]Interstitial [N, P, C]

27. Ongoing Research Greenhouse mesocosmsGreenhouse mesocosms –Nutrient attenuation during low velocity flood events Independent variableIndependent variable –Plant biomass –Nutrient source/sink

28. Acknowledgements Robert G. Wetzel The Dam Team (4-28-05) The Wundergrads US Fish and Wildlife Service Restoration Systems, LLC.