CITY OF DES MOINES SHORELINE MASTER PROGRAM

Des Moines Shoreline Inventory and Characterization
Woodmont, Redondo, and Cold Creek outlets). Shoreline activities that may impact tidal flats
(KCDNR, 2001) include:
• Coastal Bluffs and Sea Cliffs on Puget Sound, Washington (2004);
• Unnatural erosion or deposition of sediment;
• Harvesting of shellfish and other marine life;
• Fecal and chemical contamination from on-site septic systems, lawn chemicals, and
stormwater;
• Physical disturbances from shoreline armoring, marina construction, and upland
development practices;
• Shading from overwater structures; and
• Loss of emergent and riparian vegetation.
Subestuaries (Stream Mouths and Deltas)
Subestuaries are those areas of river and stream mouths that experience tidal inundation,
including their deltas and any associated marshes (KCDNR, 2001). Deltas are formed by
downstream sediment transport. This is an area where the stream or river broadens and fresh and
saltwater mix. Subestuaries function to attenuate flooding, provide juvenile salmonid feeding and
rearing habitat, acts as a transition area for migrating adult salmonids, support eelgrass beds
(depending on salinity), and provide refuge, feeding, and production areas to a wide variety of
birds, fish, mammals, and invertebrates (KCDNR, 2001). Subestuaries, especially those rich in
organic matter, can support numerous and diverse marine and estuarine invertebrates such as
polychaete worms and amphipods. These organisms near the base of the food web can be key to
overall ecosystem productivity and habitat value for fish, birds, and mammals (Robohm,
personal communication, 2005).
Subestuaries occur in all Segments within the City’s shoreline jurisdiction with the exception of
Segment B (marina), and are associated with the stream mouths of Des Moines Creek (Segment
A), Massey Creek (Segment C), McSorley Creek (Segment D), Woodmont Creek (Segment E),
Redondo Creek (Segment F), and Cold Creek (Segment G).
The growth of deltas and quality of habitat provided by the subestuaries is a factor of annual
rainfall and the rate at which sediment is transported and deposited at the mouths of streams.
High peak flows that occur as a result of increased impervious surface within the stream basin
likely transport sediment further out into Puget Sound where depths are greater resulting in
sediment accumulation beyond the stream mouth.
Shoreline activities which may impact subestuaries include:
• Physical disturbances from shoreline armoring;
• Physical disturbances from dredging and filling; and
• Changes in hydrology due to increased impervious surface within stream basins; and
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