CITY OF DES MOINES SHORELINE MASTER PROGRAM

Des Moines Shoreline Inventory and Characterization
• Nonpoint pollutant runoff from impervious surfaces and residential lawns near the
shoreline.
Eelgrass Meadows
The importance of eelgrass has been described in various sources, including the Reconnaissance
Assessment of the State of the Nearshore Environment (KCDNR, 2001). Eelgrass beds are found
in intertidal areas and provide feeding and rearing habitat for a large number of marine
organisms. Eelgrass beds have been documented in Puget Sound in the City’s shoreline
jurisdiction, in Segment A, E, F, and G (WDNR, 2001 and KCDNR, 2001). Densities are
considered patchy and not continuous (Figure 14). Shoreline activities that may impact eelgrass
(KCDNR, 2001) include:
• Clam harvesting;
• Propeller scour and wash;
• Physical disturbances from shoreline armoring;
• Shading from overwater structures; and
• Physical disturbances from dredging and filling.
Kelp Forests
The function of kelp has been described in Reconnaissance Assessment of the State of the
Nearshore Environment (KCDNR, 2001). Kelp provides habitat for many fish species, including
rockfish and salmonids, potential spawning substrate for herring, and buffers to shoreline from
waves and currents, among other functions. Kelp distribution is largely dependent upon the type
of substrate. Kelp prefers a rocky substratum for attachment. In areas where there is a
coarsening of substrate in the low intertidal and shallow subtidal zones, there is a more likely
occurrence of kelp. A change in kelp distribution may indicate the coarsening of shallow
subtidal sediments (such as that caused by erosion related to a seawall) or an increase in nutrient
loading (such as from sewage effluent). Kelp forests are not currently mapped within the City of
Des Moines shoreline jurisdiction. KCDNR (2001) indicates that it is likely that kelp
distribution has changed over time based on maps produced by the USDA in 1911-1912 and for
the Coastal Zone Atlas during the mid-1970's (Thom and Hallum, 1990). Kelp was reported as
occurring along a greater length of shoreline within all reaches of WRIA 9, which would include
the City of Des Moines shoreline (KCDNR, 2001). KCDNR also noted data gaps in general
knowledge of kelp and its biology, its role in nearshore ecological processes, lack of historical or
recent studies, and lack of distribution data.
Shoreline activities that may impact kelp densities (KCDNR, 2001) include:
• Physical disturbances from shoreline armoring, marina construction, and harvesting;
• Shading from overwater structures;
• Beach nourishment; and
• Nutrient loading.
Page 34 March 2005