Measure Amount of sediment in the coastal zone of the waters of the Great Lakes Basin.

Purpose This metric assesses the amount of water and suspended sediment entering the Great Lakes through major tributaries and connecting channels, and is used to estimate the amount of sediment available for transport to coastal ecosystems.

Features This metric offers information on climate, soil conditions, and land cover types that provide information about how such parameters affect the presence and availability of sediment to coastal ecosystems, as demonstrated by the use of remote-sensing and GIS data. Field-based collection of land cover, soil data, and surface water data can also be accomplished by: surveys (using global positioning systems); sketches; personal interviews; and record analyses at local, county, or state offices.

Limitations To conduct such measures at a broad scale, the relationships between land use, soil conditions, surface water loading, and coastal zone impacts need to be verified. This metric will need to be validated fully with thorough field sampling data and sufficient a priori knowledge of such endpoints and the mechanisms of impact. The development of indicators (e.g., a regression model using soil and topographic characteristics) is an important goal, and requires uniform measurement of field parameters across a vast geographic region to determine accurate information on calibrating such models.

Interpretation A thorough exploration of the potential hydrodynamic and biochemical relationships, with ecological functions of affected coastal ecosystems, is essential for the proper interpretation of these analyses. Human impact measures may be strongly correlated with this metric (e.g., percent agriculture or impervious surfaces within a watershed), and the pattern of such human impacts may exert a substantial influence on the results and interpretation of this metric. Because land cover is temporally variable and is non-linear in spatial and temporal patterns, this metric is complex. Thus, multiple-scale, multiple-season, multiple-year analyses of land cover and weather patterns are required to develop a robust indicator. Additionally, this indicator may perform better with greater specificity of land cover types or topography, and be most useful using contemporaneous remote sensing data. Thus, contemporary and more specific data are currently under development by EPA/ORD to improve this indicator.

Comments A thorough field-sampling protocol, properly validated geographic information, and other remote-sensing-based data could lead to successful development of this metric as an accurate indicator of coastal wetland function and ecological vulnerability. This indicator could be applied to select coastal sites, but would be most effective if used at a regional or basin-wide scale.

Metric Maps The impact of surface water runoff in the Great Lakes Basin is mapped for relevant coastal areas using remote-sensing-based geographic information. In the examples, the relative amount of surface water export of sediment throughout the entire Great Lakes Basin is demonstrated using several associated parameters. These measures could be fine-tuned to focus solely on loading to coastal wetland regions, or can be calibrated using field-based data and/or other finer scale GIS data (e.g., topographic or soil data).