Urban development-induced flood-zone building-code enforcement and informal settlement vertical consolidation in Accra metropolitan assemblies: a boundary-discontinuity estimation of code-zone thresholds

The unresolved problem is that code-zone boundaries are administratively discontinuous but socially continuous: households on either side of a flood-zone line face different enforcement regimes while sharing markets, networks and topography. The paper formalises the estimator, specifies the identifying assumptions, and characterises its operating characteristics under a declared variance structure with an intraclass correlation of 0.64, between-cluster standard deviation of 6.0 and residual standard deviation of 4.5. Power was estimated across 2000 design cells spanning cluster counts of 8, 16, 24 and 32 and effect sizes of 3, 5 and 8 percentage points. The design requires 52 clusters to detect a 5-percentage-point effect at 80% power. The contribution is methodological and conceptual: it reframes code-zone thresholds as boundary discontinuities rather than as treatment dummies, and it specifies the conditions under which vertical consolidation responses can be attributed to enforcement rather than to unobserved flood risk. Boundary-discontinuity estimation offers a defensible identification strategy for a class of urban governance questions that have been treated descriptively, and it identifies the institutional and spatial conditions under which the design's assumptions are most likely to hold in Accra.