Rain on Snow Flooding Module

created by Nic Wayand and Ryan Currier, UW Civil and Environmental Engineering

Rain on snow flooding can occur from California to the Alps. Data from a study site at Snoqualmie Pass, WA is used by students to predict how rain-on-snow flooding might change with climate change. Students review their knowledge of the earth's energy budget, then using a simple excel model, apply this knowledge to find out for themselves where the energy and heat for melting snow comes from. Students learn that the water for rain-on-snow flooding comes largely from the rain itself, with a number of forms of heat energy contributing to the <25% of the water from melting snow.

Included in the module is a background presentation on mountain snow and snow melt, some additional reading, and instructions for the hands-on-lab.

NEW! Rain on Snow Flooding Energy Balance Video (YouTube)

Powerpoint Presentation (download) includes background information on:
1. What is a Rain on Snow Flood?
2. What Causes The Snow to Melt?
3. How might Rain-on-Snow events change in the future?

Snoqualamie Field Station: Time Lapse Video

Student Handout of Excel Snow Model (pdf)
Student Handout of Excel Snow Model (word)

Snow Melt Activity: Snow melt model in excel.
Students explore model parameters to show which parts of the energy balance are important for melting snow during different weather conditions. Students relate changes in climate projections of the PNW to the snowmelt model.

Further Reading:
1. Overview of Rain on Snow Events
Kattelmann, R. (1997) Flooding from rain-on-snow events in the Sierra Nevada. Destructive Water: Water-Caused Natural Disasters, their Abatement and Control (Proceedings of the Conference held at Anaheim California, June 1996) IAHS Publ. no. 239.

2. 1996 Flood Event in Oregon
Marks, D., Kimball, J., Tingey, D. and Link, T. (1998) The senstivity of snowmelt processes to climate conditions and forest cover during rain-on-snow: a case study of the 1996 Pacific Northwest flood. Hydrological Processes, 12, 1569-1587.

3. Source for Excel Snow Model Equations
Storck, Pascal (2000) Trees, Snow and Flooding: An Investigation of Forest Canopy Effects on Snow Accumulation and Melt at the Plot and Watershed Scales in the Pacific Northwest. Water Resources Series Technical Report No. 161. March 2000. Seattle, Washington.