Impounded marshes on subsided islands:: Simulated vertical accretion, processes, and effects, Sacramento-San Joaquin Delta, CA USA

Abstract

There is substantial interest in stopping and reversing the effects of subsidence in the Sacramento-San Joaquin Delta (Delta) where organic soils predominate. Also, the passage of California Assembly Bill 32 in 2006 created the potential to trade credits for carbon sequestered in wetlands on subsided Delta islands. The primary purpose of the work described here was to estimate future vertical accretion and understand processes that affect vertical accretion and carbon sequestration in impounded marshes on subsided Delta islands. Using a cohort-accounting model, we simulated vertical accretion from 4,700 calibrated years before present (BP) at a wetland area located within Franks Tract State Recreation Area (lat 38.059, long -121.611, hereafter, "Franks Wetland")-a small, relatively undisturbed marsh island-and at the Twitchell Island subsidencereversal demonstration project since 1997. We used physical and chemical data collected during the study as well as literature values for model inputs. Model results compared favorably with measured rates of vertical accretion, mass of carbon sequestered, bulk density and organic matter content. © 2014 by the article author(s).