Andersen, Christoffer Bang

Boberg, Fredrik

Duus, Lene Bassø

Kraglund, Lene Lykke

Simonsen, Preben Dam

Thorndahl, Søren Liedtke

English

A novel method to develop continuous rainfall series for urban drainage system design and analysis is proposed, evaluated and demonstrated. The method is used to stochastically replicate historical rain series statistically as well as climate project rain series to represent specific climate scenarios and projection times. Continuous climate projected rainfall series are a crucial necessity for designing complex drainage systems and climate adaption solutions robustly for future loading as well as evaluating impacts of climate changes on the urban hydrological cycle.<br/

    Aalborg UniversitetClimate projection of rainfall series for design and analysis of urban drainage systemsThorndahl, Søren Liedtke; Andersen, Christoffer Bang; Simonsen, Preben Dam; Kraglund,Lene Lykke ; Boberg, Fredrik ; Duus, Lene BassøPublication date:2021Link to publication from Aalborg UniversityCitation for published version (APA):Thorndahl, S. L., Andersen, C. B., Simonsen, P. D., Kraglund, L. L., Boberg, F., & Duus, L. B. (2021). Climateprojection of rainfall series for design and analysis of urban drainage systems. 1. Poster presented at IWA DigitalWorld Water Congress, .General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            ? You may not further distribute the material or use it for any profit-making activity or commercial gain            ? You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.Downloaded from vbn.aau.dk on: August 24, 2021www.postersession.comAbstractA novel method to develop continuous rainfall series for urbandrainage system design and analysis is proposed, evaluated anddemonstrated. The method is used to stochastically replicatehistorical rain series statistically as well as climate project rainseries to represent specific climate scenarios and projection times.Continuous climate projected rainfall series are a crucial necessityfor designing complex drainage systems and climate adaptionsolutions robustly for future loading as well as evaluating impactsof climate changes on the urban hydrological cycle.Motivation and objectivesThe series can be used as an alternative to urban drainage designand planning design using IDF-curves or design storms. Usingcontinuous rain series as inputs to urban drainage models, it ispossible to simulate the system response and relate the response toreturn periods of exceeding critical levels rather than return periodsof the rain.The main objectives of the project (KLIMAKS) is to develop anddemonstrate application of continuous historical and climateprojected rain series, which can be applied to:1. model the complete urban hydrological cycle (e.g. including the interaction between drainage system and watercourses, infiltration excess overland flow processes, ground water infiltration to drainage system, etc.)2. model multiple function levels such as:• every-day rainfall (relevant for storm water pond filling, combined sewer overflow estimation, real-time operation and control of waste water systems and treatment plants, etc.),• design situations that corresponds to full capacity utilization (e.g. surcharging to critical levels with specific return periods), • extreme situations where system capacity is exceeded and the aim is either to investigate potential flood damage or to design adaption solutions to minimize flood damages.In this poster, we focus on stochastic generation and evaluation of rain series and stormwater detention pond design using the developed series. More details on the evaluation of rain series in urban drainage models can be found in [2].Climate projection of rainfall series for design and analysis of urban drainage systemsSøren Thorndahl1, Christoffer Bang Andersen1, Preben Dam Simonsen2,Lene Lykke Kraglund2, Fredrik Boberg3, Lene Bassø Duus41Aalborg University, Denmark; 2Niras, Denmark; 3Danish Meteorological Institute (DMI); 4Aarhus Vand, DenmarkBibliography1. Thorndahl, S., Korup Andersen, A., Larsen, A.B. (2017) Event-based stochastic point rainfall resampling for statistical replication and climate projection of historical rainfall series.Hydrol. Earth Syst. Sci. 21, 4433–4448. 2. Thorndahl, S., Duus, L.B., Simonsen, P.D., Andersen, C.B., Kraglund, L.L., Boberg, F. (2020) Klimafremskrivning af måltnedbør til afløbsteknisk anvendelse (KLIMAKS). Project report DANVA VUDP3. Thorndahl, S. and Andersen, C.B. (2021) CLIMACS: a method for stochastic generation of continuous climate projected point rainfall for urban drainage design. In review, Journal of HydrologyVUDPProject: KLIMAKS24 MAY – 4 JUNE, 2021Target climate variable Notation RCP 4.5 RCP 8.5Mean SD Mean SDAnnual precipitation ap (mm) 1.07 0.10 1.14 0.09Seasonal precipitation, winter spwi (mm) 1.12 0.11 1.24 0.13Seasonal precipitation, spring spsp (mm) 1.12 0.11 1.20 0.13Seasonal precipitation, summer spsu (mm) 1.05 0.20 0.98 0.23Seasonal precipitation, autumn spau (mm) 1.04 0.09 1.10 0.13Annual number of events above 10 mm per day n10mm (#) 1.15 0.18 1.29 0.13Annual number of events above 20 mm per day n20mm (#) 1.31 0.33 1.61 0.31Annual Maximum daily precipitation mdp (mm) 1.13 0.11 1.23 0.16Annual Maximum 5-day precipitation m5dp (mm) 1.09 0.10 1.18 0.11Rain intensity for 10 min, T=2 years d10T2 (mm/h) 1.18 0.16 1.31 0.20Rain intensity for 10 min, T=10 years d10T10 (mm/h) 1.23 0.20 1.38 0.29Rain intensity for 60 min, T=2 years d60T2 (mm/h) 1.18 0.16 1.31 0.20Rain intensity for 60 min, T=10 years d60T10 (mm/h) 1.23 0.20 1.38 0.29Rain intensity for 360 min, T=2 years d360T2 (mm/h) 1.18 0.16 1.31 0.20Rain intensity for 360 min, T=10 years d360T10 (mm/h) 1.23 0.20 1.38 0.29Stochastic sampling and climate projectionRain series are stochastically generated to represent the currentclimate (1980-2010) and climate scenarios RCP 4.5 and 8.5 in2070-2100. Individual rain events are sampled from a referencetime series season by season and scaled to represent changes inrainfall intensity. The time between events is sampled from a two-component exponential distribution to represent a change in thetime between events in the future climate. The overall concept is togenerate a large ensemble of rain series and evaluate them against anumber of different climate variables (Tab. 1). The procedure isdescribed in Fig. 2 and more details can be found in [1] and [3].For each climate scenario, the top 100 rain series with the lowestweighted errors between climate parameter target and realizationare selected for further analysis. The results are show in fig. 4 asboxplots for annual precipitation, seasonal precipitation, extremesand the three climate scenarios. The boxplots illustrate aggregatedresults of all realizations and the boxplot variability thereforerepresent both the year-to-year variability as well as the uncertaintyrelated to climate projection.Fig. 3 shows IDF curves for each climate scenario.Design of stormwater pondsThe generated rain series are applied for simple design of stormwater detention ponds with different outlet flow rates for aconnected catchment area of 1 ha. The procedure serves thepurpose to investigate the variability between the acceptedrealizations in each climate scenario ensemble and to exploredifferences in design volumes depending on the design parametersand choice of the climate scenario.Fig. 5 shows design volumes as function of return period for afixed outlet flow rate of 1 l/s/ha. Fig. 6 shows volumes with outletflow rates of 0.5, 1.0 and 5.0 l/s/ha for a 5-year return period.The difference in required storage volumes between current climateand future climate scenarios are shown in fig. 7 as function ofoutlet flow rate. The fact that RCP 8.5 has larger intensities butlonger drought periods between rain events works in favor ofsmaller outlet flow rates.Conclusion• We can generate series that represent RCP 4.5 and 8.5 in theyear 2100.• We show how rain series can be applied to the design ofstormwater detention ponds.• There are large uncertainties in climate projections, which giveslarge variability between generated series. An ensemble of rainseries is therefore recommended for application.• The stormwater pond design showcases the importance ofapplying continuous rain series which include changes inmultiple climate parameters and not only the extreme rainfall.

Climate projection of rainfall series for design and analysis of urban drainage systems

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Climate projection of rainfall series for design and analysis of urban drainage systems

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