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Urban Snowmelt Processes: Modelling and Observation

Semadeni Davies, Annette LU (1999)
Abstract (Swedish)
Popular Abstract in Swedish

I Norra Skandinavien, liksom i andra kalla områden, är oftast de urbana dräneringssystemen inte kapabla att föra bort de stora volymer smältvatten som ofta belastar systemet under flera veckor under snösmältningen. Högt vattenflöde till reningsverk, översvämning av kombinerade system och låg vattenkvalitet är några problem förknippade med snösmältning. Trots detta är rapporter om snösmältningsprocesser ovanliga i den hydrologiska litteraturen. Denna avhandling behandlar forskning om snöhydrologi i Luleå. De fyra målsättningarna är: att undersöka (a) det rumsliga förhållandet av snösmältningsegenskaper och landanvändning; (b) urbaniseringens effekter på snösmältningsprocesserna; (c) smältvattnets... (More)
Popular Abstract in Swedish

I Norra Skandinavien, liksom i andra kalla områden, är oftast de urbana dräneringssystemen inte kapabla att föra bort de stora volymer smältvatten som ofta belastar systemet under flera veckor under snösmältningen. Högt vattenflöde till reningsverk, översvämning av kombinerade system och låg vattenkvalitet är några problem förknippade med snösmältning. Trots detta är rapporter om snösmältningsprocesser ovanliga i den hydrologiska litteraturen. Denna avhandling behandlar forskning om snöhydrologi i Luleå. De fyra målsättningarna är: att undersöka (a) det rumsliga förhållandet av snösmältningsegenskaper och landanvändning; (b) urbaniseringens effekter på snösmältningsprocesserna; (c) smältvattnets effekter på hydrologin i den urbana miljön; och (d) möjligheter att modellera urbana snösmältningsprocesser. Dessa målsättningarna är behandlade i fem artiklar (Papers). Artiklarna I och II undersöker hur den urbana miljön påverkar snösmältningen. Artikel III behandlar den säsongsmässiga variationen av vattenflödena inom staden. Artikel IV presenterar en snötaxering som bekräftar antaganden gjorda i artiklarna II och III. Artikel V är en litteratursammanställning som ifrågasätter validiteten av urbana avrinnings modeller baserat på erhållna resultat i de tidigare artiklarna.



Urbanisering är förknippad med extrem heterogenitet och minskad ytgenomsläpplighet. Den urbana hydrografen har högt toppflöde som kommer med liten tidsfördröjning till och med efter kortvariga regn med låg intensitet. Snösmältningsprocesserna är de samma i både rurala och urbana områden, men klimatet och snöns egenskaper skiljer sig väsentligt. Till exempel så plogas urbana områden i hög grad. Avrinningen genererad från snösmältning är vidare komplicerad eftersom det finns en mer uttalad termisk komponent av vattenbalansen jämfört med regnhändelser. Energiflödena i snöpacken är i hög grad påverkade av den urbana miljön. Snösmältningen är tidigare och mer intensiv på grund av den ökade strålningen på sydsidan av byggnader jämfört med nordsidan av byggnader eller öppen mark. Urban snö har ett lägre albedovärde och högre densitet än rural snö, vilket leder till snabbare smältning.



Effekten av yttyp och snötäckets egenskaper på dag- och avloppsvattenflödena visas. Förutsägelser av avloppsvattenflödet förbättras av ytmässig vägning av snötyp genom a priori antagande om snöegenskaper och täckning. Till exempel så minskar snötäckningen och andelen ostörd snö om landanvändningen intensifieras. Således så brukar snöhögar i förorterna ligga på genomsläppligt underlag, medan snöhögar i centrum brukar ligga på asfalt. Säsongsmässiga skillnader av avrinningsvolymer och flödesvägar till avloppsreningsverk och recipient studerades med en enkel vattenbalansmodel. Ökad avrinning, minskade koncentrationstider och långvariga avrinningshändelser leder till hög belastning i reningsverket. Ytvattenkomponenten av avloppsvattnet kommer från direkt inflöde i brunnar och infiltration till avloppsledningar. Dagens metoder för att förutsäga urban snösmältning befanns vara otillräckliga. Graddagsmetoden är olämplig för urban tillämpning. Men brist på data för att utveckla, testa och använda mer sofistikerade modeller hänvisar den urbana ingenjören till denna metod. (Less)
Abstract
In northern Scandinavia and other cold regions, urban drainage systems are often unable to cope with the high volumes of melt water which can be sustained for several weeks. High waste water treatment plant inflows, combined system overflows and low water quality are a few problems associated with snowmelt. However, reports detailing urban snowmelt processes are lacking in the hydrological literature. This thesis reports research into the snow hydrology of the City of Luleå, Sweden. There are four objectives: to investigate (a) the relationship between snow and landuse; (b) the effects of urbanisation on snowmelt processes; (c) the effect of melt water on urban hydrology; and (d) the feasibility of modelling urban snowmelt processes. These... (More)
In northern Scandinavia and other cold regions, urban drainage systems are often unable to cope with the high volumes of melt water which can be sustained for several weeks. High waste water treatment plant inflows, combined system overflows and low water quality are a few problems associated with snowmelt. However, reports detailing urban snowmelt processes are lacking in the hydrological literature. This thesis reports research into the snow hydrology of the City of Luleå, Sweden. There are four objectives: to investigate (a) the relationship between snow and landuse; (b) the effects of urbanisation on snowmelt processes; (c) the effect of melt water on urban hydrology; and (d) the feasibility of modelling urban snowmelt processes. These are met in a series of five appended papers. Papers I and II investigate snowmelt sensitivity to the urban environment. Paper III concerns seasonal patterns of the town water balance. Paper IV presents a snow survey that reaffirms the assumptions about snow cover and characteristics made in Papers II and III. Paper V is a literature review that questions the validity of urban runoff routing models on the basis of findings from the earlier papers.



Urbanisation is associated with extreme heterogeneity and diminished surface permeability. The urban hydrograph shows high peak flows and rapid responses after short, low intensity events. Snowmelt processes are the same in both rural and urban areas, but climate and snowpack properties differ greatly. Urban snow, for instance, is subject to ploughing. Snowmelt induced runoff generation is further complicated by a more pronounced thermal component of the water balance compared to rain events. Snowpack energy fluxes are greatly influenced by the urban environment. Melt is earlier and more intense due to enhanced radiation to the south of buildings in comparison to snowpacks in open ground or to the shaded north. Urban snow has low albedo and high density than that of rural snow leading to speeded melt.



The role of surface type and snow cover characteristics upon storm- and waste water inflow is demonstrated. Predictions of waste water inflow are improved by spatially weighting snow types according to a priori assumptions of snow properties and coverage. For instance, the proportion of undisturbed snow coverage decreases as landuse intensity increases. Snow piles in suburbs tend to be on permeable ground, but they are more likely to be on sealed surfaces in the central city. There are seasonal differences in runoff volumes and flow pathways to the waste water treatment plant and receiving waters. Increased volumes of runoff, reduced concentration times and long event duration lead to high waste water loads at the treatment plant. The surface water component of sewage originates from direct flow into pipe inlets and infiltration into sewer pipes. Current methods of estimating urban snowmelt, such as the degree-day method, and runoff are found to be problematic. However, a lack of data for developing, testing or operating more sophisticated models restricts urban engineers. (Less)
Please use this url to cite or link to this publication:
author
opponent
  • Prof. Buttle, James, Dept. Geography, Trent University, Canada
organization
publishing date
type
Thesis
publication status
published
subject
keywords
geographical and geological engineering, Hydrogeology, energy, runoff, snow properties, heterogeneity, hydrological modelling, Urbanisation, snowmelt, Hydrogeologi, teknisk geologi, teknisk geografi, Geophysics, physical oceanography, meteorology, Geofysik, fysisk oceanografi, meteorologi
pages
177 pages
publisher
Department of Water Resources Engineering, Lund Institute of Technology, Lund University
defense location
V:B, V-huset, John Ericsson väg 1.
defense date
1999-05-21 10:00
external identifiers
  • other:ISRN: LUTVDG/TVVR-1026(1999)
ISSN
1101-9824
language
English
LU publication?
yes
id
a1820ceb-b354-4da9-87af-c26874842732 (old id 39622)
date added to LUP
2007-08-01 11:36:41
date last changed
2016-09-19 08:44:53
@phdthesis{a1820ceb-b354-4da9-87af-c26874842732,
  abstract     = {In northern Scandinavia and other cold regions, urban drainage systems are often unable to cope with the high volumes of melt water which can be sustained for several weeks. High waste water treatment plant inflows, combined system overflows and low water quality are a few problems associated with snowmelt. However, reports detailing urban snowmelt processes are lacking in the hydrological literature. This thesis reports research into the snow hydrology of the City of Luleå, Sweden. There are four objectives: to investigate (a) the relationship between snow and landuse; (b) the effects of urbanisation on snowmelt processes; (c) the effect of melt water on urban hydrology; and (d) the feasibility of modelling urban snowmelt processes. These are met in a series of five appended papers. Papers I and II investigate snowmelt sensitivity to the urban environment. Paper III concerns seasonal patterns of the town water balance. Paper IV presents a snow survey that reaffirms the assumptions about snow cover and characteristics made in Papers II and III. Paper V is a literature review that questions the validity of urban runoff routing models on the basis of findings from the earlier papers.<br/><br>
<br/><br>
Urbanisation is associated with extreme heterogeneity and diminished surface permeability. The urban hydrograph shows high peak flows and rapid responses after short, low intensity events. Snowmelt processes are the same in both rural and urban areas, but climate and snowpack properties differ greatly. Urban snow, for instance, is subject to ploughing. Snowmelt induced runoff generation is further complicated by a more pronounced thermal component of the water balance compared to rain events. Snowpack energy fluxes are greatly influenced by the urban environment. Melt is earlier and more intense due to enhanced radiation to the south of buildings in comparison to snowpacks in open ground or to the shaded north. Urban snow has low albedo and high density than that of rural snow leading to speeded melt.<br/><br>
<br/><br>
The role of surface type and snow cover characteristics upon storm- and waste water inflow is demonstrated. Predictions of waste water inflow are improved by spatially weighting snow types according to a priori assumptions of snow properties and coverage. For instance, the proportion of undisturbed snow coverage decreases as landuse intensity increases. Snow piles in suburbs tend to be on permeable ground, but they are more likely to be on sealed surfaces in the central city. There are seasonal differences in runoff volumes and flow pathways to the waste water treatment plant and receiving waters. Increased volumes of runoff, reduced concentration times and long event duration lead to high waste water loads at the treatment plant. The surface water component of sewage originates from direct flow into pipe inlets and infiltration into sewer pipes. Current methods of estimating urban snowmelt, such as the degree-day method, and runoff are found to be problematic. However, a lack of data for developing, testing or operating more sophisticated models restricts urban engineers.},
  author       = {Semadeni Davies, Annette},
  issn         = {1101-9824},
  keyword      = {geographical and geological engineering,Hydrogeology,energy,runoff,snow properties,heterogeneity,hydrological modelling,Urbanisation,snowmelt,Hydrogeologi,teknisk geologi,teknisk geografi,Geophysics,physical oceanography,meteorology,Geofysik,fysisk oceanografi,meteorologi},
  language     = {eng},
  pages        = {177},
  publisher    = {Department of Water Resources Engineering, Lund Institute of Technology, Lund University},
  school       = {Lund University},
  title        = {Urban Snowmelt Processes: Modelling and Observation},
  year         = {1999},
}