Seawall & Bulkhead Guide: Cape Cod, MA

How Fast Cape Cod's Shoreline Actually Moves -- and Why the Range Matters

USGS Circular 1417 gives directly citable figures for the Outer Cape: the overall bluff section retreats at an average of roughly 3 feet per year, with a more recent study showing this rate has roughly doubled in places. Within that same stretch, the rate itself varies -- North Truro comes in lower, at approximately 1.5 feet per year, while Coast Guard Beach in Eastham runs higher, at approximately 3.5 feet per year. These are the best-documented, most directly sourced numbers behind this page, and they already show meaningful town-to-town variation before you even leave the Outer Cape.

Older secondary summaries citing USGS/Woods Hole Oceanographic Institution erosion-history work push the range further. During the 1938-1974 period, Wellfleet and Truro saw rates from as low as a few inches per year up to 9 feet per year at the high end, and Chatham's North Beach barrier -- a dynamic, storm-reshaped barrier spit -- ranged roughly 3 to 19 feet per year across different periods within that same window, with some areas reportedly jumping to 13 feet per year since 1994. That 19-feet-per-year figure, even as a historical high rather than a current annual average, is the kind of number that makes clear why shoreline hardening is a live, recurring topic in some parts of this county and not others.

Correction to an earlier version of this research: it had attributed a specific "+1.3 feet per year" Cape Cod Bay accretion figure to Harwich. That doesn't hold up -- Harwich fronts Nantucket Sound, not Cape Cod Bay, and has no Cape Cod Bay shoreline at all. No primary source located since has named any specific Cape Cod Bay town with a quantified accretion rate; that figure has been dropped rather than repeated. What the correction doesn't change is the underlying point it was trying to make: erosion severity, and therefore the case for or against a seawall or bulkhead, is not a county-wide constant. Chatham's North Beach barrier system is the real, verifiable example of a Cape Cod shoreline that both erodes and builds new land in the same stretch -- it has broken and reformed repeatedly (1987, 2007, and again in May 2025), a genuinely different dynamic from a stable mainland bluff. Each individual Cape Cod town page in this cluster will need to establish its own local erosion picture rather than borrowing this region-wide range.

Three Different Shorelines, Three Different Hardening Conversations

Cape Cod isn't one shoreline type, and that matters for anyone thinking about hardening a specific piece of it. Atlantic-facing ocean bluffs and beaches -- the Outer Cape stretch covered by USGS Circular 1417 above -- carry the highest documented erosion rates in the source research, and are the setting most people picture when they think "Cape Cod erosion."

Cape Cod Bay-facing shores are a genuinely different, more variable situation. Rates there can run lower than the Atlantic side, and a dynamic barrier system like Chatham's North Beach shows shorelines on this peninsula can build new land in one spot while eroding another nearby -- meaning a bay- or sound-facing property's hardening calculus can look nothing like an ocean-facing one even within the same town.

The Cape Cod Canal's own shoreline is a third category entirely, and arguably not a "residential hardening" question at all: it has been federally managed by the U.S. Army Corps of Engineers since 1928, when the Corps took over the canal from its original private owner, eliminated tolls, and later widened and deepened it in the 1930s. That's a different maintenance regime, funding source, and decision-making authority entirely from a private homeowner's seawall or bulkhead -- worth knowing simply so it isn't confused with the private residential hardening questions the rest of this page addresses.

The Cape Cod Commission: A Regional Layer Most Coastal Regions Don't Have

The Cape Cod Commission was created by the Cape Cod Commission Act, enacted by the Massachusetts legislature in 1989 and signed into law in January 1990, explicitly because 1980s development pressure threatened the region's natural, coastal, historical, and cultural values. It's a genuine regional land-use regulatory agency, not a merely advisory body, and it holds two powers directly relevant to shoreline-hardening decisions specifically: Development of Regional Impact (DRI) review, which gives it authority to review and regulate large or regional-scale projects that cross town lines or exceed local-impact thresholds -- independent of, and in addition to, whatever a town's own permitting process requires -- and District of Critical Planning Concern (DCPC) designation, the ability to recommend special protective zoning over environmentally or culturally sensitive areas.

What that means in practice for a seawall or bulkhead project here: a substantial shoreline-hardening structure, especially anything larger than a routine repair, could potentially trigger DRI review at the regional Commission level in addition to whatever a town's Conservation Commission or building department separately requires. This is a genuinely distinctive regulatory layer -- most single-town coastal jurisdictions don't have a regional body with this kind of binding authority sitting above local permitting. This page cannot tell you whether any specific project would trigger that review; it's a threshold question worth raising directly with both the relevant town and the Cape Cod Commission early in the planning process, not something to assume either way.

What This Research Didn't Find: The Wetlands Act, Conservation Commissions, and Costs

Here is the honest limit of this page. The research behind it confirmed the erosion severity and range described above, the region's distinct shoreline types, and the Cape Cod Commission's regional regulatory powers -- but it did not gather Massachusetts' specific Wetlands Protection Act procedures, any individual town Conservation Commission's actual review requirements, state coastal engineering permitting rules, realistic seawall or bulkhead construction costs, or any hard-armoring restrictions specific to Cape Cod. None of those figures appear anywhere in the source research for this page, and inventing them here would risk handing a reader a wrong number or a wrong process to plan real construction around -- so this page deliberately doesn't do that.

One pattern worth flagging, with a clear caveat: Massachusetts coastal construction, including shoreline hardening, commonly requires review under the state Wetlands Protection Act, administered locally through each town's own Conservation Commission. That's a common Massachusetts coastal-town pattern worth checking for -- it is not something this research independently verified as a confirmed rule for any specific Cape Cod town, and it should be treated as a starting question for the relevant Conservation Commission, not an assumed answer. Requirements, review timelines, and what qualifies for an exemption versus a full hearing can vary town by town even within this one county.

Before You Plan Any Shoreline Structure

Seawall, bulkhead, and other shoreline-hardening decisions on Cape Cod are subject to Massachusetts environmental permitting and Cape Cod Commission review that both change over time. Confirm current requirements directly with the relevant town's Conservation Commission, the Cape Cod Commission, and a licensed coastal engineer before making any decision about an oceanfront, bay-front, or canal-adjacent property here. Nothing on this page is engineering, permitting, or legal advice.