You are here:
Can Oregon marshes keep up with the rising tide? A study of short and long term marsh accretion - CERF 2015
Citation:
MochonCollura, TChris, C. Brown, Ted DeWitt, C. Janousek, AND C. Cornu. Can Oregon marshes keep up with the rising tide? A study of short and long term marsh accretion - CERF 2015. Coastal Estuarine Research Federation, Portland, OR, November 08 - 12, 2015.
Impact/Purpose:
Marshlands bordering nine Oregon estuaries were studied to determine their susceptibility to sea level rise. Our research suggest that low marshes, those sections of the marsh that are more frequently overtopped with medium to moderate flood tide waters, may be able to keep pace with the current rate of sea level rise through sediment accretion. Less often flooded high marshes accrete at a rate less than half that of the lower marsh. As sea level continues to rise, current high marsh plant communities will most likely shift to those of the adjacent low marsh.
Description:
More frequent inundation of Oregon coastal marshlands associated with rising sea level threatens these important and diverse habitats. Accretion rates determined by the marker horizon method and longer term peak Cs137 detection in nine marsh systems from Coquille to Tillamook were found to vary depending on a number of factors including plot elevation and plant species present. From 2009 to 2013, marker horizon plots in the low marsh generally accreted more, with a maximum observed accretion rate of 2.3 cm y-1 at one Carex lyngbyei dominated plot directly adjacent to the lower Siletz River. Inundated less frequently, high marsh plots had lower annual accretion rates which were often times below the current rate of sea level rise for the region. These results agree with long term accretion rates determined from Cs 137 deep (~0.5 m) cores. Our results suggest that low marsh habitat in Oregon estuaries may be able to keep pace with the current rate of sea level rise. Accretion rates from this study will also be compared to other rates in the region and data gaps identified.