Point B-17

Current standing

The measured line of sight (LOS) velocity is +0.3 mm/yr (95% CI ±1.1 mm/yr), with 1.8 mm of cumulative motion over the 9.6 year observation window.

Within its district, this point sits at the 19th percentile of motion magnitude: its motion is unremarkable for the district.

The leading mechanism hypothesis is thermal or moisture cycle (confidence 60%); annual periodic component of ±2.3 mm, peaking around month 2.

A seasonal component of ±2.3 mm dominates the record, peaking around month 2; this oscillation reflects thermal or moisture cycling, not ground loss, and has been separated from the trend estimate.

Forward look

If the observed trend persists, the linear model projects cumulative motion of 4.4 mm (±4.1) within 5 years and 5.7 mm (±4.8) within 10 years.

Note that the record contains a trend break around 2022-10 with motion accelerating by 1.8 mm/yr; if the post break rate persists, projections above are conservative and the point should be re-evaluated at the next epoch.

At the current differential rate against point B-06, angular distortion would approach the published serviceability reference (1/500) in beyond a 100 year horizon at current rates, and the structural damage risk reference (1/150) in beyond a 100 year horizon at current rates. These are reference criteria from published literature; site specific limits are set with the client's geotechnical team.

Exposure band, share of reinstatement value

Band spans the published damage ratio range for the projected damage grade at each horizon, bracketed by the measurement confidence interval. Midpoint shown for reading only.

Horizon detail

Proactive intervention under monitoring tends to be materially less costly than reactive repair. As a qualitative cross-hazard anchor, the NIBS study reports mitigation spend returning on the order of six to one on average. This is a cross-hazard average, not a settlement specific figure, and is offered as an order of magnitude framing only.

Foundation guidance, screening level

Shallow foundations viable with monitoring

Total settlement references follow KB section 3: isolated footings on sand near 25 mm and raft foundations near 50 mm over structure life, not annual rates.

Eurocode 7 Annex H is treated as informative, and hogging tolerance values are taken as approximately half of the sagging values.

Piled towers transfer load below the fill, so ground level infrastructure such as roads, pipes, plazas and villas on shallow foundations is the layer these references most concern.

Consolidation stage · primary

Young fill context. On more recent fill placed Excavated coastal ground, not island fill, higher absolute rates can be a normal part of ongoing consolidation, so grading is best framed against deviation from the fitted consolidation curve rather than the absolute velocity.

Structural sensitivity references

Differential settlement tolerance depends on the structural system and the span, so there is no single threshold. As published reference tiers, angular distortion near 1/750 concerns settlement sensitive equipment, 1/500 references first architectural cracking, 1/300 references panel wall cracking and visible tilting, and 1/150 references structural damage to general buildings. Taller and stiffer structures on piled foundations tend to transfer load below the fill, so the ground level layer is where these references most apply. Site specific tolerances are set with the client's geotechnical engineer.

Measurement constraints

• Measurement geometry caveat. Sentinel-1 measures line of sight motion, which is not vertical. Reported at 0.3 mm/yr line of sight, the near vertical approximation is about 0.4 mm/yr, and this figure is labelled as an approximation pending ascending and descending decomposition.
• Sampling caveat. The record spans the 2022 to 2025 single constellation period, during which sampling was reduced and the velocity confidence bounds widen across that window.
• Horizontal motion caveat. North south horizontal motion is essentially invisible to Sentinel-1 given its near polar orbit, so any north south component is not captured and this limitation is stated explicitly.

Watch items

• Any recent loading change nearby (construction, dewatering, stockpiling) that could explain the acceleration

Monitoring cadence

Heightened: review at every new satellite epoch (approximately every 12 days), with quarterly expert review

Ground verification trigger

Ground verification (levelling or targeted geotechnical inspection) is recommended if the current behavior persists across the next two quarterly reviews

Configured alert thresholds