Lake Huron doesn’t recognize property lines. Sarnia’s shoreline policy shouldn’t either

Sarnia plans to spend nearly $30 million on shoreline protection over the next decade, but Lake Huron does not follow property lines. We argue the City needs a coast-wide strategy that accounts for sediment movement, public infrastructure and private benefits, along with a clear policy for deciding who should pay.

Sarnia’s maps divide the Lake Huron shoreline into roads, parks, municipal rights-of-way and private properties. The lake, of course, does not. Waves, currents, sediment, beaches, bluffs and the lake bottom interact along the coast regardless of where one property ends and another begins.

That should be the starting point for how Sarnia manages its shoreline.

After decades of erosion-control work, the City’s latest 10-year capital plan still contains $29.8 million for shoreline protection. Its asset-management plan estimates that Sarnia’s shoreline infrastructure requires roughly $3.3 million in annual reinvestment and rates its overall condition as poor. Shoreline protection is no longer an occasional emergency expense; it has become a permanent category of municipal infrastructure.

That makes two questions increasingly important: what treatment makes sense for the coastline as a whole, and how should the cost of that treatment be divided?

The first cannot be answered one property at a time.

The St. Clair Region Conservation Authority’s shoreline plan explains that waves and currents move sediment along Lake Huron through a process known as littoral drift. That does not mean the entire coast is one uninterrupted sediment conveyor. Natural features divide it into littoral cells and reaches, but those physical boundaries bear little relationship to property lines.

Across the conservation authority’s Lake Huron study area, including Sarnia, the net potential movement of sand is generally from northeast to southwest. Eroding bluffs and the nearshore lake bottom supply some of the sediment that forms beaches farther along the coast.

In other words, erosion in one place can help maintain a beach somewhere else.

That means stopping erosion is not environmentally neutral. A revetment may successfully protect the land behind it while also reducing a source of sediment entering the wider coastal system. Groynes can trap sand and help build a beach on their updrift side, but in doing so can change how much sediment continues farther downshore.

It would be wrong to claim without detailed modelling that one particular Bright’s Grove project has caused erosion at another property. But it is equally wrong to treat every shoreline project as though it exists in isolation. The conservation authority itself warns about cumulative reductions in sediment supply, potential downdrift erosion and the shortcomings of uncoordinated shoreline protection.

That also complicates the usual distinction between public and private benefit.

A privately owned bluff can contribute sediment to a public beach. A municipal groyne can influence sediment moving past private properties. A publicly funded revetment can simultaneously protect City property or infrastructure while benefiting homes immediately behind it.

The proper unit for deciding what should be built is therefore the coastal reach, not the individual lot. Once the best treatment for that reach has been established, Sarnia can then decide how the cost should be shared.

Bright’s Grove provides the clearest test.

The City’s asset plan identifies 4.9 kilometres of shoreline there, including three kilometres owned by the municipality. Those three kilometres alone have an estimated replacement value of almost $48.8 million.

Between Mike Weir Park and the Cull Drain, Sarnia also owns the abandoned Old Lakeshore Road right-of-way. A 2022 engineering study examined rebuilding roughly 775 metres of deteriorated shoreline while creating public access along it. The estimated project budget was $14.6 million plus HST in 2022 dollars.

There is an obvious public benefit. Reconstructing the shoreline could protect and re-establish municipal land while creating a significant public waterfront connection.

But 25 private properties also adjoin the right-of-way, and rebuilding it would stabilize the municipal strip immediately in front of them.

Both benefits are real. It would be misleading to divide $14.6 million by 25 and describe the result as a subsidy to each homeowner, because much of the project concerns public land and public access. It makes just as little sense, however, to assume the direct private benefit is worth nothing.

Ontario already gives municipalities a mechanism for making that distinction. Provincial local-improvement rules specifically cover retaining walls, dykes, breakwaters, groynes and other shore-protection works, allowing municipalities to identify an owners’ share and a municipal share and levy special charges against abutting or immediately benefited properties.

Sarnia does not necessarily need to start billing waterfront homeowners for every metre of armour stone. It should, however, have a clear policy explaining how it determines whether a private contribution should be zero, 10 per cent, 50 per cent or some other amount.

That cost-sharing policy should sit within a broader and updated coastal strategy.

Sarnia currently relies on the St. Clair Region Conservation Authority’s Lake Huron Shoreline Management Plan, principally developed through a 2011 update and itself drawing on coastal studies dating to 1989 and 1992. Those studies remain valuable, but the City is now planning another generation of shoreline infrastructure under different costs, development patterns and environmental pressures.

A modern strategy should examine the coast by physical management units, accounting for sediment sources and movement, beaches and dunes, existing groynes and revetments, public infrastructure, private development and public access. Each proposed project could then be evaluated for its effects on the whole relevant reach rather than only the property immediately behind it.

That would mean asking whether a structure protecting one asset could affect a neighbouring beach, whether beach nourishment or dunes could do part of the work, whether infrastructure could reasonably be moved inland, and whether coordinated protection would perform better than isolated projects. It should also force the City to consider what each new structure will require taxpayers to maintain decades from now.

None of this means Sarnia should stop protecting Bright’s Grove. In places where roads, utilities, public land and established homes already sit beside the lake, retreat may be impractical or enormously expensive.

Nor should the discussion become an attack on waterfront homeowners. They bought homes in neighbourhoods the municipality chose to establish, service and maintain. But those past choices should not automatically become a promise to hold every metre of shoreline in precisely the same location forever, regardless of environmental consequences or cost.

Sarnia needs a straightforward principle: **manage the coast collectively and allocate the costs fairly.**

That means deciding what works environmentally before dividing the bill financially. Public roads, utilities, ecological functions, municipal land and public access are legitimate public expenses. Exceptional direct benefits to private properties should at least be identified and considered when costs are allocated.

It also means evaluating beaches, dunes, vegetation and other natural or hybrid approaches alongside armour stone where practical, and being clear about which sections of shoreline Sarnia intends to defend indefinitely.

The sand moving southwest along this coast does not stop at a survey stake, and waves do not know whether the land behind them is public or private. Sarnia cannot manage that system one backyard at a time.

It should manage the shoreline as a connected coast first, then decide openly and consistently how the costs of holding that coast in place should be shared.