Determining Dredging Priorities

The Department of Natural Resources and Environmental Control (DNREC) is using stakeholder input to develop a data-based method to prioritize dredging projects in Delaware’s Inland Bays.

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Sierra Davis
Division of Watershed Stewardship

From June to November of 2019, DNREC used online and in-person surveys to gather public input on the navigability of Delaware’s Inland Bays. The survey was available online and was shared at three public open houses in fall of 2019 at locations in and around the Inland Bays.

The survey received more than 1,000 responses, the majority from residents of Sussex County and the Inland Bays area. The survey responses  provide valuable information that will help guide the planning and prioritization of dredging projects in Delaware’s Inland Bays.

Navigable Inland Bays Channels

Inland Bays ChannelsThere are 17 navigable channels in Delaware’s Inland Bays, located entirely within Sussex County, Delaware, maintained by the state and federal governments.

Three — Indian River Inlet and Bay Channel, the Lewes-Rehoboth Canal and Massey’s Ditch — are federally-authorized channels. Maintenance performed by the state on federally authorized channels, such as the 2020 Massey’s Ditch project, is coordinated with the U.S. Army Corps of Engineers and U.S. Coast Guard.

More than 500 survey participants reported that they boat on Indian River Inlet and Bay Channel, indicating that this is one of the most heavily used channels in the Inland Bays.  Over 400 participants responded that they boat on Assawoman Canal, Little Assawoman Bay Channel, Massey’s Ditch and Rehoboth Bay Channel.

Survey Results

Inland Bays Survey Response by Zip CodesThe dredging prioritization survey was available between June and November of 2019. It received 1,033 responses from 83 different ZIP codes in five states. While the survey reached a wide geographic extent, nearly 90% of surveys completed were from residents of Sussex County, Delaware.

Motor boating was reported as the most popular activity in the Inland Bays among survey participants, followed by fishing, crabbing, kayaking, sailing, having a waterway-based business and clamming.

Survey participants ranked three criteria highly for prioritizing dredging projects in Delaware:

  1. Navigability and the location of sediment shoaling
  2. Channels Connecting Major Bodies of Water
  3. Safety, including boater traffic and locations of groundings reports

DNREC is actively collecting data to address these criteria, and others, which will help prioritize dredging projects.

Channel Depth

In 2019, DNREC surveyed the depth of all 17 state-maintained waterways in Delaware’s Inland Bays. The data collected provides a baseline condition of navigability, identifies areas of shoaling and helps to determine and plan how much sediment might need to be removed from channels.

Continued depth surveying over the years will help monitor hot spots for sediment shoaling in the waterways. The surveys also help determine placement locations for channel markers.

Channels Connecting Major Bodies of Water

Many channels provide passage from one body of water to another in the Inland Bays. The dredging prioritization survey shows that considering these channels a dredging priority is of high importance to users.

Channels connecting major bodies of water in the Bays include Assawoman Canal, The Ditch, Indian River Inlet and Bay Channel, the Lewes-Rehoboth Canal, Little Assawoman Bay Channel, Massey’s Ditch, Rehoboth Bay Channel and White Creek.

Boater Safety in Delaware’s Inland Bays

Keeping channels open and safe is a mission of DNREC’s Shoreline and Waterway Management Section and was ranked as a factor that should be considered when prioritizing dredging. To enhance understanding of hazards and safety concerns in the Bays, DNREC is beginning to monitor boat grounding report locations with the help of local boat towing companies. These data will help inform locations where increased depth monitoring and potential dredging should occur.

Additional Considerations

DNREC must consider a wide range of factors when planning a dredging project, including those related to feasibility and economics.  These are some of the most important factors to ensure we remain focused on DNREC’s Vision and Mission and to ensure long term sustainability and success of our Waterway Management Program.

Sediment Disposal

An important part of each project is locating an area for dredged sediment disposal. Due to increased development in the Inland Bays region, the number of upland sediment disposal sites has decreased. In response, DNREC is exploring creative options for sediment disposal including beneficial use of dredged sediment. Beneficial use projects might include using the sediment for beach replenishment, as used for the 2020 Massey’s Ditch project, or wetland restoration.

Environmental Impacts

There are time-of-year restrictions for dredging projects in Delaware’s Inland Bays meant to protect sensitive habitats and species from the impacts of dredging. Typically, dredging can only occur in the Inland Bays from November to March.

Each project must obtain a State Subaqueous Lands and Water Quality Permit, a U.S. Army Corps of Engineers Permit, and Federal Consistency Determinations from the Delaware Coastal Management Program.

Access to Public Boat Ramps and Marinas

DNREC is taking steps to update maps of new public boat ramp and marina facilities. This will help inform dredging project decisions for improving waterway access in Delaware.


The cost of a project must also be considered. Project cost can vary based on the amount of sediment that needs to be removed, sediment type, scheduling considerations, and the pumping distance to a disposal site.