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Prime Hook Then and Now: A Restoration Story

Written on: September 7th, 2016 in Wetland Restorations

prime hook units

*Updated 9/12/16

A hot topic for scientists and residents of Milton as of late, has been the Prime Hook National Wildlife Refuge Marsh Restoration project. This Refuge had multiple breaches in its freshwater impoundments where saltwater from the Delaware Bay cut its way through the dunes. The breaches caused significant flooding; massive vegetation die offs, and returned the habitat from its man-made freshwater system to its historic slightly salty brackish system.

To solve these problems, the Prime Hook National Wildlife Refuge took on one of the largest restoration projects in the U.S. in the fall of 2015. The end goal, to create a self-sustaining system and return all the impoundments to a brackish tidally influenced ecosystem. The Refuge closed breaches, created over 20 miles of channels, planted thousands of plants, scattered thousands of seeds by airplane throughout the landscape, and provided design input for DelDOT’s new bridge.

So how will they know if it worked?

That’s where we (the Wetland Monitoring & Assessment Program) come in and help. In the summer of 2015, we provided baseline wetland monitoring before any restoration work had begun. Then, after the Refuge finished this summer we came back to do the first post restoration sampling.

Preliminarily, we have seen some remarkable changes in the landscape.

Two of our assessment points now have a channel flowing through them. This makes it harder to walk around our sites, but should provide some interesting data in the future on channel impacts to a developing wetland.

Prime Hook National Wildlife Refuge assessment site before restoration

Prime Hook National Wildlife Refuge assessment site before restoration

One of the most visually noticeable changes is the lack of water in some of the assessment sites. Sites that were once completely covered with water pre-restoration now appear high and dry post-restoration even though they do not have any significant elevation change.

But, the most promising response to the restoration is the colonization in these open areas with various plant species; Bulrush, Common Rush, Sweetscent, and Marsh Hemp to name a few. Leptochloa fascicularis, Bearded Sprangletop, is a salt tolerant annual that has become more prevent and responded to the new and changing conditions. As expected, the plant communities are changing, and will continue to change and adjust over the next few years.

The same Prime Hook National Wildlife Refuge assessment site after restoration work.

The same Prime Hook National Wildlife Refuge assessment site after restoration work.

We are just starting to dig into our data, and will continue to monitor the Prime Hook National Wildlife Refuge Marsh restoration for the next three years in the hopes to better understand how wetland restorations change the landscape and return the vital wetland functions that we count on everyday.


What We Looked At – Quick & Dirty:

  • 20 points throughout the 4 units (impoundments)
  • Collected data on:
    • Below and Above Ground Biomass
      • The collection of biomass will provide us information on how healthy the marsh is by looking at the roots below the ground and the aboveground growth. We cut the aboveground growth and bag it, then took a round cylinder and drove it into the marsh surface to a depth of 30cm. This marsh plug would then be rinsed off of all the mud, sand, crabs, and mussels from the sample, the remaining plant material is then sorted of live and dead, as well as the above ground growth. The samples are then put in an oven to dry and be weighed after 72 hours.
    • Bearing Capacity
      • The bearing capacity looks at the ability of the soil to support specific loads that we will impart, we will apply a standard force with a slide hammer 5 times and record the depth of impact it has on the marsh surface.
    • Horizontal Vegetation Obstruction Readings
      • The horizontal vegetation obstruction is looking at the visual obstruction through the marsh at 5 specified heights, this is done by having one person go 4 meters away and look through the marsh vegetation at the 5 heights and count how many squares they can see on a profile board that is divided into 10 squares.
    • Elevation Surveys
      • The elevation surveys will be done by using a Real Time Kinematic satellite navigation in the same locations at every point, a 5 by 3 plot of points at 3 cardinal directions from our point for a total of 45 points at each location.

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