Snowmelt and runoff in urban areas in Luleà, north Sweden, are discussed and compared with rural conditions. The uneven snow distribution in cities is quantified. Energy fluxes at the snow surface in different environments are estimated. It is shown that, mainly because of increased absorbed radiative energy in the snow, the daily melt is about 10 mm higher in the city than in rural environments. In the course of prolonged snowmelt, the infiltration capacity of most soils in urban areas becomes so reduced that melt-induced peak flows from grassed and gravelled surfaces are similar to those from asphalted surfaces. When rain falls on snow, overland flow may take place from the entire area of a basin. La fonte des neiges urbaine et l'écoulement dans la nord de la SuèdeRésumé La fonte des neiges et l'écoulement dans des zones bâties à Luleâ sont discutés et comparés avec des conditions rurales. La répartition inégale de la neige dans les villes est déterminée. Le flux d'énergie à la surface du neige dans des différents mileux est estimé. Dans la phase avancée d'une fonte des neiges prolongée les débits maximaux des surfaces couvertes de graviers ou d'herbes sont similaires aux ceux des surfaces asphaltées.

Empirical characteristics of snowmelt runo are derived from observations made during snowmelt in a six-year period from 1980 to 1985 on three experimental plots and three plates located on the campus of the Lulea University of Technology in Lulea, Sweden. The plots had asphalt, gravel and grass surfaces. The plates were of dierent designs with one having the bottom cut out so that it was more like a frame. With the assumption that the asphalt surface of the plots was impervious, in®ltration of meltwater into gravel and grass surfaces was deduced. Unlike rainfall in®ltration, the graph of snowmelt in®ltration rate resembled a¯ow hydrograph, with a distinct rise, a peak and a distinct recession. A strong linear relationship between the snowmelt runo hydrograph peak and the snowmelt amount was found, which explained more than 90% of the variability in the snowmelt peak. This is in contrast with rainfall runo where the relationship between runo peak and volume is decidedly nonlinear. Hourly snowmelt runo peak and daily snowmelt amount were found to exhibit nearly constant skew and follow approximately a Gumbel frequency distribution.

The bolometer and radiant energy. h c. Am. Acad. Arts Sci., 16, pp. 342-358-(1883) The selective absorption of solar energy. Am. 3. Sci., 25, pp. 169-196-(1884) Researches on solar heat and its absorption by the Earth's atmosphere (Report of the Mount Whimey Expedition). h$ Pap. Signal Sew., 15, pp. 11, 42, United States War Department, Washington-(1885) Observations on invisible heat and the recognition of hitherto unmeasured wavelengths , made at the Allegheny Observatory. h c. Am. SOC.

Vertical movement of snowmelt water through snowpacks is modelled by applying the kinematic wave theory. Analytical solutions are obtained for moisture flux, particle velocity, time history and velocity of meltwater front and total moisture content for a single melt event assuming that the melt rate is constant. These solutions are extended to the case involving more than one event. © 1997 by John Wiley & Sons Ltd.

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