US Department of Commerce

 

Date of this Version

2012

Citation

Remote Sensing of Environment 119 (2012) 243–254; doi:10.1016/j.rse.2011.12.018

Abstract

Sediment loading is one of the primary threats to the health of the Chesapeake Bay.We have developed a high resolution (250 m) ocean color satellite tool to monitor sediment concentrations in the Bay. In situ optical and sediment sampling is used to develop a total suspended matter (TSM) algorithm for the Chesapeake Bay. The Coastal Optical Characterization Experiment (COCE) is part of an ongoing effort to optically characterize processes and to develop regional remote sensing ocean color algorithms in the coastalwaters. The goal is to characterize sediment concentrations and to develop a tool to track plumes cascading down the Bay following heavy rainfall events. Background TSMconcentrations in the Chesapeake Bay Watershed can also be characterized. The plumes can have potentially devastating effects on the Chesapeake Bay's fragile ecosystem by increasing nutrient loads, depositing sediments, and decreasing salinity and light levels. Sampling took place throughout 2006 to 2008 in the upper andmid portions of the Chesapeake Bay.Measurements of TSM, chlorophyll a (Chl), and hyperspectral optics were collected. The optical measurements included above water surface irradiance (Es(λ)), in-water downwelling irradiance (Ed(λ)) and in-water upwelling radiance (Lu(λ)). These optical data were used to analyze the performance and utility of the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua Band 1 (645 nm) for use as a TSM monitoring tool. From the optical measurements we have derived a 3rd order polynomial regression of TSM to normalized water-leaving radiance (r2=0.79) to form an algorithm that quantitatively relates TSM to the MODIS 250 m resolution band 1 (645 nm). The algorithm performance was validated (a mean percent difference of −4.2%) against 270 total suspended solids samples collected by the Chesapeake Bay Program during routine water quality monitoring of the Chesapeake Bay environment. The TSM algorithm tool is then used to demonstrate monitoring of significant runoff events that occurred in June, 2006 and March, 2008. In addition, the utility of the Chesapeake Bay TSM product is demonstrated by describing regional and seasonal variations in sediment concentrations throughout the Chesapeake Bay for 2009. Mean concentrations ranged from11.55 mg/l in the upper Chesapeake Baywinter season to 6.37mg/l in the middle Chesapeake Bay spring season. These remote sensing tools can be valuable instruments in the detection and tracking of runoff events and background concentration for monitoring the health and recovery of the Chesapeake Bay.