I think it stands for "otros riesgos hidrometeorológicos":

"Ante esta experiencia, resulta adecuado modificar la decimaoctava y vigésima de las Reglas para la Constitución e Incremento de las Reservas de Riesgos en Curso de las Instituciones y Sociedades Mutualistas de Seguros, a fin de establecer, de manera específica, la forma en que se deberá constituir y valuar la reserva de riesgos en curso de los seguros de huracán y otros riesgos hidrometeorológicos."
http://www.cnsf.gob.mx/Normativa/InstReglas/ReglasCNSF/153 A...

"Normatividad de los Seguros de Huracán y otros Riesgos Hidrometeorológicos"
http://www.ama.org.mx/prest/nshyo.pdf

The word "hydrometeorological" does exist in English:

"National Weather Service
Hydrometeorological Prediction Center"
http://www.hpc.ncep.noaa.gov/

And it is sometimes used like this, for example by the OECD:

"Catastrophic Risk and Insurance
Hurricane and hydrometeorological risks"
http://www.oecd.org/dataoecd/39/30/36816744.pdf

So I think you could use it. But in practice I think it means more or less "severe weather risks".



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Note added at 33 mins (2012-06-11 21:07:11 GMT)
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"Other related hazards" does make very good sense, but why is it in English?

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Note added at 37 mins (2012-06-11 21:10:53 GMT)
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Can't seem to find "ORH" for this either, but my second reference doc., http://www.ama.org.mx/prest/nshyo.pdf , does have the "Sistema RH-MEX", in which I think "RH" stands for "Riesgos Hidrometeorológicos"; the whole document is about that in relation to insurance.

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Note added at 38 mins (2012-06-11 21:11:40 GMT)
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This "Sistema RH-Mex" crops up in a number of places.

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Note added at 40 mins (2012-06-11 21:13:55 GMT)
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Make that Other Hydrometeorological Hazards:

"Hydrometeorological hazard
UN/ISDR - UN Intl Strategy for Disaster Reduction Sec [ 15 January 2009 ]
Definition:
Process or phenomenon of atmospheric, hydrological or oceanographic nature that may cause loss of life, injury or other health impacts, property damage, loss of livelihoods and services, social and economic disruption, or environmental damage.
Comment: Hydrometeorological hazards include tropical cyclones (also known as typhoons and hurricanes), thunderstorms, hailstorms, tornados, blizzards, heavy snowfall, avalanches, coastal storm surges, floods including flash floods, drought, heatwaves and cold spells. Hydrometeorological conditions also can be a factor in other hazards such as landslides, wildland fires, locust plagues, epidemics, and in the transport and dispersal of toxic substances and volcanic eruption material"
http://www.preventionweb.net/english/professional/terminolog...

Lots more refs to this term.