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Site analysis: natural hazards and climate risk at the location

A building stands in the same spot for sixty years. What hazards that spot is exposed to determines insurability, maintenance effort and, increasingly, financing. The question is not new; what is new is that it now has to be answered.

What this is about

Not a weather forecast, but a classification: how strongly is this site affected compared with others, and what follows from that for the building standing on it.

The five hazards in question

  • Heavy rainfall. Not the watercourse nearby, but water that does not drain away. Affects sites with no flood exposure at all.
  • Flooding. River flooding and rising groundwater are two different questions with two different answers.
  • Heat. More relevant to operation than to the fabric: cooling load, comfort, technical plant.
  • Storm. Roof, façade and everything fixed to them.
  • Hail. The damage most often underestimated, because it rarely hits the structure and almost always the envelope.

Publicly available hazard maps from the German states answer the first two for the location. What they do not answer is the question about the building: where the finished ground level lies, where the basement windows are, how the roof drains, how high the plant stands.

Why the building data belongs with it

A hazard map knows grid cells, not buildings. It says an area is affected — not whether the opening the water would run through sits twenty centimetres above the governing water level.

Precisely those figures arise during a survey anyway: terrain heights in DHHN2016, opening levels, roof geometry, the position of technical plant. The same survey that produces the terrain and surface model and the orthophoto also yields the values a site assessment works with. No second visit is needed.

When the need arises

  • Acquisition due diligence, when risk feeds into the price
  • Reporting obligations for which site risks have to be evidenced
  • Insurance discussions after a loss or ahead of a reassessment
  • Refurbishment planning, when protective measures are to be designed in rather than retrofitted later

Further reading