Storm surge

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Storm surge

Useful links

Statens Kartverk Sjø 
Statens Kartverk – link to everything about storm surge.
Meterologisk Institutt – height of the water – table.
Meterologisk Institutt– tidal water and height of the water.

What is a storm surge?

Storm surge occurs at a combination of high water and strong onshore wind, i.e a combination of astronomic tidal water and a meteorological contribution.

The contribution from the storm does not necessarily have to hit shore.
The low pressure and the onshore wind can stay offshore, so the only feeling we get is an increase in the height of the water.

Meteorological contribution.

Onshore wind and low pressure will cause an increase in the height of the water.

High pressure and off-shore wind will reduce it.

The contribution from the tidal water can be calculated and Statens Kartverk Sjø issues annually tables with timing for high and low water (expressed as expected tidal water) for a number of ports.

The meteorological part is not predictable to the same extent.

HAT -  Highest astronomic tidal water – highest flood tide, leaving out the meteorological influence on the water level.

LAT – Lowest astronomic tidal water .
Common reference level  in the charts from January 1, 2000 for the countries surrounding the North Sea. The lowest tidal water which will occur on a given place (the lowest water level, ignoring the meteorological influence)

In practice HAT and LAT is calculated based on the tidal water tables for 18,6 years, being the astronomical cycle.

Chart cero.

Chart cero is the reference level for water depths in the charts and water heights in the Tidal Water Table. Level cero in the charts, is placed so low – for safety reasons – that the water height rarely falls below this level. The difference between the middle level and level cero depends on the size of the tidal water and is largest in the Northern part of Norway where the tidal water differences are the biggest.

In areas where the variations in the tidal water are small compared to the influence of the weather on the water level, chart cero is for safety reasons placed lower than LAT. In Norway this applies to the coast of the Southern part of Norway and the Oslo fiord, where the water level over a long period (often up to 1 – 2 weeks) is lower than LAT. Chart cero is of this reason placed 30 cm lower than LAT in the inner part of the Oslo fiord (inside Drøbaksundet) and 20 cm lower alongside the coast from the boarder to Sweden and to Utsira (Rogaland) For the rest of the country, including Svalbard, chart cero is equal to LAT.

Criteria for compensatable damage caused by a storm surge.

The water level is over a 5 year return period, i.e. considerably over HAT (Even if 5 year return is a mean value,  the frequency of lower water level should indicate that the occurrence of damage at a lower water level, falls outside the companies’ fundamental claim that damage shall occur sudden and unexpected)

NOTE; Water level gauges do not measure the actual effect from the wash of the waves (the whole contribution), but this is something which has to be brought into consideration by the surveyor  (who contacts Statens Kartverk Sjø or Meterologisk Institutt when needed)!

Relation to storm (meteorological contribution not necessarily in immediate nearness)
Water (in the above connection) floods onshore (flooding)

Primarily it is the water’s damaging qualities which are the cause of the claim(in above connections)

Damages caused by the wash of the waves are in this connection also compensatable.

(For the record, the expression “spring tide” (used colloquially) is in itself not a condition for compensation, but a regular appearance of in particular high water approximately at the same time as vernal and autumnal equinox)

Practical handling.

If there is any doubt at all, the problem shall be placed before the experts in Statens Kartverk Sjø, alternatively after additional information has been achieved from the Port Authorities at the place of the damage.

In individual cases this information shall be obtained by the surveyor.  At more serious incidents, it must be considered if this information shall be obtained centrally. 

Even if there is a storm surge, there will be certain damages which will not be compensated.  Boats in mooring may cause damage by “knocking” against the wharf or quay.  This is looked upon as an indirect damage and will accordingly not be defined as a damage directly caused by a natural disaster.  Relevant appeal case 25/94.

In § 2, 2nd paragraph of Naturskadeforsikringsloven it says:

“ Should the insurance company find when handling a claim that an area is particularly exposed to avalanches, landslides or other natural events, cf § 20 of Naturskadeloven, the company shall notify the municipality concerned as soon as possible”

The notification to the municipality shall be in writing,  if necessary by using form in enclosure 15.

If a prohibition to build or parcel has been issued according to § 22 of Naturskadeloven, no compensation will be paid for damage to constructions which later on have been erected on that location or for personal chattels which may be in the construction, if the damage is of such nature that it is covered by the prohibition.

In cases where the damaged property in particular is exposed to natural damage and the repair costs will amount to 60% or more of the insurance sum of the damaged construction (building excluding the ground), the company will according to § 3 – 2nd paragraph of the Instructions of The Pool and the condition for the natural perils insurance, also compensate  the increase in the claim resulting from a prohibition to rebuild or repair.  It is a warranty for such compensation that a statement according to §  22, 2nd paragraph of Naturskadeloven is being registered on the property.

Storm surge – rules of deduction.

All physical objects being in or near coastal areas are in particular exposed to damages. Weaknesses in the construction combined with long-lasting influences will often be factors which trigger off damages.  The combination of poor maintenance (e.g. rust/rot), erosion, washing of waves, defective stiffening arrangements etc. must be evaluated.  Age and conditions are in other words very important.

If the Claimant is more than little to blame, these circumstances may give reason for deductions according to the law.

Adequate causation and recurrence are relevant factors in an evaluation whether reduction in the compensation should be made based on negligence.  It is therefore important to investigate whether similar damages have occurred earlier, and if so, when and if other persons have had damages in the same area.

If the claimant is more than little to blame for not having prevented after previous damages, those circumstances may give reasons for reduction in the compensation according to the law.
The condition for deduction is that the surveyor has described the possibility of preventing damage in his report and that the claims handler expressly has required the claimant to have preventive work done.

If a potential reduction in the compensation for personal chattels is being considered, be in particular aware when these objects are damaged because they are stored low or directly on the ground – or on the wharf/quay – and the claimant is more than little to blame for not having moved his property or done any other relevant measures to prevent damage when a storm surge has been predicted.

Storm surge – exposed objects.

All objects being close to the seaside is exposed to damages caused by storm surge. In particular exposed are floating stages, wharf/quays (see subject heading) and boathouses.

Handling instructions.

The damage shall be surveyed and debited The Pool according to guidelines in the settlement conditions.  The survey report shall state the costs of repair with no deductions, the physical conditions of the objects and the settlement amount to The Pool..  Be in particular aware of the guidelines regarding compensation for damage to pipelines with connected equipment.

The claims handler must be aware of the fact that the compensation to the client shall be based on the company’s own conditions.(See pattern report – enclosure no20)

Exposed location.

• Placed on low ground.
• Near the sea.

Previous damages.

• See the chapter about repeated damages.


• Consider if this has been done.

Exposed objects.

Wharfs, quays
Floating stages.
Other objects near the sea.
Furnished basement.
Objects placed in the basement.
Objects stored on low ground
Objects stored on wharf/quay

Circumstances around weaknesses in the construction

Developed over time
Poor maintenance
Erosion over time
Washing of waves over time
The strength reduced over time
The exceptions (does not apply to storm surge)
Breaking up of the ice
Indirect damage
Damages caused by vessel/boat ( cfr. appeal case 25/94)

Special circumstances.

Recourse (See separate chapter)
Municipal injunctions

Clearance after a damage.(drying, hygrometry, inspection sheet) See the chapter about clearance after a damage.
Registration (60% rule) See the chapter about registration.
Damage caused to foundation/damage caused by subsidence (inspection by leveling)
Contamination (The Nutrient Supervision, Council Doctors)
Following up of larger damages.  See chapter about larger damages.

Appeal cases.

33/92 Damage caused by washing of the waves caused by storm surge – natural damage
14/94 Barrels of herring – exposed storage.                                          – 100% deduction
46/94  Wharf side shed – erosion over time                                         - no natural damage
Boathouse – sliding out over time, poor foundation, plain concrete                                                                                 - no natural damage
71/95 Cargo – known risk/not moved                                                  - 100% deduction
2/03  Damages over time                                                                     - no natural damage