A Tour of Living Shorelines

This area was experiencing erosion within the existing riprap. There was an interest to see if it would be possible to green-up the riprap and reduce the erosion.

Plant-based materials and oyster shell bags were used in front of rip rap to create a marsh habitat:

• Coconut fiber coir logs: stabilize marsh edge, and trap new sediment behind it to build up marsh elevation
• Coconut fiber mats: help to hold coir logs in place on marsh
• Wooden stakes: help to hold coir logs in place on marsh
• Clean sand: used to raise the height of the land to the appropriate growing conditions for wetland plants when there is not enough time to let it fill in naturally or the local sediment supply in the water is not enough
• Native plants: “green-up” the shoreline, and trap and secure sediments with stems and roots to further stabilize marsh
• Oyster shell bags: help defend coir logs from wave energy, and provide surface for natural oyster recruitment

This project has regained marsh in front of the riprap, although the plants have been slow to fill in the defined space. This is possibly due to the use of clean sand fill.

This area has fairly low wave energy, so natural materials could be used with no rock components to stabilize the banks from further erosion:

• Coconut fiber coir logs: stabilize marsh edge, and trap new sediment behind it to build up marsh elevation
• Coconut fiber mats: help to hold coir logs in place on marsh
• Wooden stakes: help to hold coir logs in place on marsh
• Native plants: trap and secure sediments with stems and roots to further stabilize marsh

This project has prevented further marsh erosion, but the abundance of groundwater seeps and unconsolidated bottom has presented a challenge in re-establishing the marsh edge to historic conditions.

This area experiences wave energy from boat wakes in the Lewes-Rehoboth Canal and has lead to erosion of the shoreline.

Plant-based materials were used and were armored on the outside by recycled oyster shells to stabilize the banks from further erosion:

• Coconut fiber coir logs: stabilize marsh edge, and trap new sediment behind it to build up marsh elevation
• Coconut fiber mats: help to hold coir logs in place on marsh
• Wooden stakes: help to hold coir logs in place on marsh
• Native plants: trap and secure sediments with stems and roots to further stabilize marsh
• Oyster shell bags: help defend coir logs from wave energy, and provide surface for natural oyster recruitment

This project has successfully regained marsh and elevation.

 DNREC Wetland Monitoring & Assessment Program 

 Partnership for the Delaware Estuary 

This area was experiencing marsh erosion in front of the marina. In an attempt to stabilize the area, the landowners placed pieces of cinder block and other materials on the shoreline, but to no avail. The decision was made to see if a living shoreline could be installed to encourage sediment and plants to fill in over the cinder block material.

Plant-based materials were used and were lined at the edge by recycled oyster shells to break up the waves:

• Coconut fiber coir logs: stabilize marsh edge, and trap new sediment behind it to build up marsh elevation
• Coconut fiber mats: help to hold coir logs in place on marsh
• Wooden stakes: help to hold coir logs in place on marsh
• Native plants: trap and secure sediments with stems and roots to further stabilize marsh
• Oyster shell bags: help defend coir logs from wave energy, and provide surface for natural oyster recruitment

Marsh plants have successfully filled in the site and the hard stabilization features can no longer be seen. It has also been reported that local fisherman now visit the site to capture bait fish, which had not been a profitable venture before at this location.

This area was experiencing erosion in the bend of a tidal creek that was threatening an existing roadway.

This area has relatively low wave energy, so natural, plant-based materials could be used with without rock components to line the edge of the creek:

• Coconut fiber coir logs: stabilize marsh edge, and trap new sediment behind it to build up marsh elevation
• Coconut fiber mats: help to hold coir logs in place on marsh
• Wooden stakes: help to hold coir logs in place on marsh
• Native plants: trap and secure sediments with stems and roots to further stabilize marsh
• Oyster shell bags: help defend coir logs from wave energy, and provide surface for natural oyster recruitment

Marsh plants have successfully filled in the site, helping to stabilize the marsh edge and prevent further erosion.

This area was experiencing erosion of a small strip of marsh that blocks saltwater from entering a managed freshwater impoundment.

In an attempt to stabilize the area and regain ground in the face of moderate to high wave energy, a hybrid living shoreline design approach was used that combined natural materials, rocks, and sand:

• Rock sill: reduce wave energy by intercepting incoming waves, and keep or trap new sediment behind it to build marsh elevation, while having gaps to allow wildlife connection to land
• Clean sand: raise the height of the land to the appropriate growing elevation for wetland plants when there is not enough time to let it fill in naturally, or if the local sediment supply in the water is not enough
• Oyster shell bags: line rock sill openings to reduce wave energy and retain sand, and provide surface for natural oyster recruitment
• Native plants: trap and secure sediments with stems and roots to further stabilize marsh

Marsh plants have successfully established and are filling in the sand strip, helping to stabilize the shoreline. The project has persisted with no damage through high water levels brought by Hurricane Dorian in August of 2019, showing that the rock sill is successful at helping to reduce wave energy and that the natural components were resilient in the face of a large storm.

Read Avenue - Dewey Beach, Delaware

2019

This area has a low elevation and a high percentage of land covered by pavement, buildings, and other impervious surfaces. Erosion was occurring as well as flooding due to stormwater runoff, high tides, and storm surges.

This innovative hybrid project integrated a living shoreline and stormwater management retrofit in order to reduce polluted runoff and protect the reestablished wetlands.

Project design and permitting began in 2017 and construction was completed in late 2019. Plants were installed in the spring of 2020.

So far, after a number of large rain events, there as been no surcharge flooding.