Dear @Rogerio @Jan @Fulvio,

Thanks for your input and useful documents.

@Rogerio

Some notes!

To the "First Observation", what about FLOODS?

The floods are also is a type of river flow.

While we design the large dams and risk of several water engineering projects based on the flood return period (Let say instantaneous peak discharge).

To the "Second Observation",

What we mean by "HEAVY SNOW", the heavy snow has higher water equivalent (you are right), but I want to focus on the damages caused by snow height in its solid form (as a hydrological component) or heavy snowfall (as an extreme hydrologic event).

Through the past week most cities of Iran from west to east have been blanketed under heavy snow which has crippled the residents. Northern Iran has been hit by its heaviest snowstorm in 60 years and faced the worst problems. The roofs of many houses and public facilities have collapsed under heavy snow.

The snow height/weight can be used as a measure by urban designer/architects to prevent/reduce undesirable consequences of extreme snowfall events. (Like Flood Return Period for Hydrologic Engineers)

May be a link between snow hydrology and disaster management to reduce the economic losses.

Just my point of view based on a little knowledge.

Sure! You need a sufficiently long dataset to perform statistical analysis.

Dear Raoof Mostafazadeh

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First observation: Do not forget that in hydrology snowfall is defined as a type of precipitation.

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Second observation: It is easier to work with equivalent height of water than snow height, and generally the amount of precipitated snow in rain gauges are heated and transformed into equivalent water height.

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Third observation: The problem of flood events are generally not correlated with the height of precipitated snow, but the intensity of the melting acting upon snow accumulated.

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I fully agree with the response of Rogerio Maestri. Further I add a number of manuscripts which might be inspiring.

2nd manuscript

3rd manuscript

4th manuscript

5th and last manuscript

Dear @Rogerio @Jan @Fulvio,

Thanks for your input and useful documents.

@Rogerio

Some notes!

To the "First Observation", what about FLOODS?

The floods are also is a type of river flow.

While we design the large dams and risk of several water engineering projects based on the flood return period (Let say instantaneous peak discharge).

To the "Second Observation",

What we mean by "HEAVY SNOW", the heavy snow has higher water equivalent (you are right), but I want to focus on the damages caused by snow height in its solid form (as a hydrological component) or heavy snowfall (as an extreme hydrologic event).

Through the past week most cities of Iran from west to east have been blanketed under heavy snow which has crippled the residents. Northern Iran has been hit by its heaviest snowstorm in 60 years and faced the worst problems. The roofs of many houses and public facilities have collapsed under heavy snow.

The snow height/weight can be used as a measure by urban designer/architects to prevent/reduce undesirable consequences of extreme snowfall events. (Like Flood Return Period for Hydrologic Engineers)

May be a link between snow hydrology and disaster management to reduce the economic losses.

Just my point of view based on a little knowledge.

Dear Raoof,

I am not quite sure what you do actually intend. In other words: how do you want to sample the "snow height of heavy events"? Keep in mind that an application of extreme values statistical concepts to, e.g., daily values of the snow height is prohibited since the values will expose a strong auto-correlation.

With kind regards,

Andy

Thanks for your useful comments and suggested references.

According to Rogerio, the amount of precipitated snow in gauge stations are heated and transformed into equivalent water height.

I mean that we can record the height of isolated snowfall events on a snowboard. (same as the recorded maximum level of river stage in flood events)

Thus we have the highest recorded snow height for each year.

And, the return period of snow can be established using a sufficiently long dataset through statistical analysis (as suggested by Adriana). Not sure the annually maximum snow depth is recorded in snow gauges!

The right method - which I applied in the studies uploaded in my profile on ResearchGate - is to install a net of measuring points surprising all slope aspects, a significant range of altitudes and a significant range of vegetal cover. In every measuring point are instaled snowpack rods to measure the hight of snowpack. By expeditionary travel from point to point it will be taken the hight at rod and with a densitometer (a simple roman balance with a calibrated cilinder) the water equivalent of snow. You need also some thermograps - better is hygrothermografs - instaled also in a net.

This method is reliable for small watersheds (under 10 sqkm). For larger watersheds it can be used data from the weather stations.

Taking only height, without a correlation with temperatures, wind, may involve wrong interpretations. That because of the high variability of snow density with temperature and wind during the snow fall. There are frequent events of great damages in forest stands for example, caused by snow, even if the height of snowpack is low, and that because of positive values of air temperature during the snow fall, which involve a high density of snow. Combined with low temperature of brances and leafs a great amount of water is blocked at the level of canopy cover as iced water or icy snow.

Of course, to answer directly to your question, is possible to use the concept of return period as for flooding or rain, if you have enough data to build a proper probability distribution of events.

The concept of return period to annual maximum snow height and snow fall has been applied in this paper:

https://www.researchgate.net/publication/227149771_Long-term_changes_in_annual_maximum_snow_depth_and_snowfall_in_Switzerland_based_on_extreme_value_statistics

The snow load code to prevent the collaps of infrastructure is usually based on the concept return period and the measurement and modeling of maximum snow water equivalent. Here an example from the EU:

http://books.google.ch/books?id=l4IvF1CVDtwC&pg=PA226&lpg=PA226&dq=european+snow+load+return+period

or

http://onlinelibrary.wiley.com/doi/10.1002/pse.62/pdf

Article Long-term changes in annual maximum snow depth and snowfall ...

Dear Raoof,

As you know, you should apply extreme value analysis for these types of problems. You may find the following presentation useful. A time dependent Generalized extreme model is used for analysis of extreme snow events.

http://www.cces.ethz.ch/projects/hazri/EXTREMES/talks/MartyDavosJan11.pdf

@ Raoof.

At your quote on February 10 that due to large snowfalls "The roofs of many houses and public facilities have collapsed under heavy snow." I want to draw attention to something that goes unnoticed during the crisis that occurs during these events.

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In regions with constant snowfall usually these structural effects do not occur, but in regions where these falls are episodic or fall is not very abundant there is a "loss of memory" of the architects and engineers on care that is taken in colder countries , the slope of the roof. I know that in northern Iran the amount of snow is more abundant and may not be the case.

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In southern Brazil the most abundant snow falls are rare with recurrence period of about 50 to 100 years (remember that it's not too south in the southern hemisphere is cooler!), But in the winter of 2013 was one such event, covering almost the entire southern region of 600m above 800m, as the roofs were not calculated for this charge, several public and private facilities such as gymnasiums for schools, industrial buildings and other collapsed due to the inadequacy of the architecture used (insufficient slope!).

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I call attention to this factor, because many times we are concerned with the intensity of snow and forget adequate building codes, to give an example I show some links on these occurrences:

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http://saojoaquimonline.com.br/saojoaquimdefato/?p=7819

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http://alconpat.org.br/2013/07/24/prejuizos-com-a-neve-municipio-do-planalto-norte-catarinense-decreta-situacao-de-emergencia/.

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http://m.diariocatarinense.com.br/noticias/todas/a4210988

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The snowfall is unusual, picturesque and tourist apparel in Brazil, but when it occurs it shows the inadequacy of the architecture to the event, even if it is of the order of 15cm to 20cm!