Jakarta, Oct. 16 -- As land subsidence and rising sea levels increasingly threaten Indonesia's coastal areas, debates over development often focus on how high protective seawalls should be.

Yet a more decisive issue is whether coastal protection investments can preserve the economic value of the areas they are designed to protect over the long term.

If physical risks, maintenance costs, and changes in land values are not factored in from the outset, coastal protection projects could create major infrastructure assets whose costs continue to rise.

The burden would ultimately fall not only on the projects themselves but also on public budgets and economic activities that depend on coastal areas.

Java's northern coast offers the clearest...