Severe flooding events in recent years have underlined the importance of accurate hydrological modelling in urban areas. There are many important parameters relating to both the rainfall distribution and properties of the land on which the rain falls that controls the impacts of the rain event. While the importance of input parameters such as initial water content, topography and extent of hardened surfaces is widely known, their impact on hydrological response in urban areas is not thoroughly understood. In 2017, scientists from the Swedish Meteorological and Hydrological Institute, SMHI, presented five empirical hyetographs based on long-term Swedish municipal rain data (Olsson, et al., 2017). The hyetographs vary in location of peak and distribution of intensity. Olsson (2019) evaluated the hydrological response in terms of water depth of the hyetographs in relation to Chicago Design Storm (CDS), a common design storm used in Swedish hydrological modelling, and found that CDS nearly always overestimates the hydrological response in comparison to the empirical hyetographs, meaning historical rainfall intensity distributions, developed by SMHI.  The aim of this thesis is to analyse the robustness of empirical hyetographs by conducting a sensitivity analysis of a generic urban model with a variation of input parameters. A statistical analysis of data on hardened surfaces, topography and initial water content was conducted to find the median, 5th and 95th percentile respectively of the range of values in Swedish conditions. These values were applied to a synthetic urban model and run together with the five empirical hyetographs and CDS in MIKE 21. The results indicate that the empirical hyetographs are not very robust relating to variations in infiltration capacity (initial water content and amount of hardened areas), while they are more robust when varying the topography. The variation of topography also resulted in large variations in water depth, time to peak and extent of flooded area, while variation of initial water content and amount of hardened surfaces had smaller, although still clear, effects. Furthermore, the results show that hyetographs with a late peak are more sensitive to variations in initial water content and hardened surfaces than hyetographs with an early peak. On average, CDS estimates the response in comparison to the empirical hyetographs accurately, with an average overestimation of 0.5%, but does not capture the range and complexity of the empirical hyetographs. Including the frequency of the different hyetographs, CDS gave an overestimation of 5% compared to the empirical hyetographs. The highlight the uncertainty in using CDS as input for urban cloudburst modelling, but limitations in form of catchment properties in a study area and the importance of the input values limits the generability of the study. / De senaste årens allvarliga översvämningshändelser har understrukit vikten av noggrann hydrologisk modellering i stadsområden. Även om betydelsen av parametrar som initial vattenmättnad, topografi och andelen hårdgjorda ytor är allmänt känd, är deras inverkan på urban hydrodynamisk modellering inte helt klarlagd. Under 2017 presenterade forskare från Sveriges Meteorologiska och Hydrologiska Institut, SMHI, fem empiriska hyetografer baserade på långvariga kommunala regndata (Olsson et al., 2017). Hyetograferna varierar i fördelning av intensitet och tidsmässig placering av maxintensitet. Olsson (2019) utvärderade hyetografernas hydrologiska respons i relation till Chicago Design Storm (CDS), en vanlig designstorm som används i svensk hydrologisk modellering, och fann att CDS nästan alltid överskattar responsen i jämförelse med de empiriska hyetograferna.  Syftet med detta examensarbete är att analysera robustheten hos de empiriska hyetograferna genom att utföra en känslighetsanalys av en generisk stadsmodell med en variation av ingångsparametrar. En statistisk analys av data om hårdgjorda ytor, topografi och initial vattenmättnad genomfördes för att hitta median, 5:e respektive 95:e percentilen av värdena i svenska förhållanden. Dessa värden applicerades på en generisk stadsmodell och kördes tillsammans med de fem empiriska hyetograferna och CDS i MIKE 21. Resultaten indikerar att de empiriska hyetograferna inte är helt robusta vad gäller variationer i infiltrationskapacitet (initial vattenmättnad och andel hårdgjorda ytor), medan de är mer robusta vid variation av topografin. Variationen av topografi resulterade också i stora variationer i vattendjup, tid till maxflöde och utbredning av översvämmat område, medan variation av initial vattenmättnad och mängden hårdgjorda ytor hade mindre, men fortfarande tydliga, effekter. Vidare visar resultaten att hyetografer med sen topp är känsligare för variationer i initial vattenhalt och hårdgjorda ytor än hyetografer med tidig topp. I genomsnitt uppskattar CDS responsen från de empiriska hyetograferna korrekt, med en genomsnittlig överskattning på 0.5%, men fångar inte omfånget och komplexiteten hos de empiriska hyetograferna. Inräknat frekvensen av de olika hyetograferna gav CDS en överskattning på 5 % jämfört med de empiriska hyetograferna. Resultaten belyser osäkerheterna i att använda CDS regn som drivdata i skyfallsmodelleringar för stadsplanering, men begränsningar i form av markegenskaper i ett enskilt studieområde och vikten av modellens initialvärden begränsar dock generaliteten för studien.

From the Proceedings of the 1972 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 5-6, 1972, Prescott, Arizona / Numerous reports from the southwest claim that soil moisture prior to rainfall-runoff event has no influence on the resulting flow volumes and peak rates. Runoff occurs from many storms that would not be expected to produce runoff, and an explanation lies in the occurrence of antecedent rains. This hypothesis is tested by dividing runoff events into 2 subsets--one with no rain within the preceding 120 hours, and the other with some rain within the preceding 24 hours--and to test the null hypothesis. The hypothesis was tested with rainfall and runoff data from a 40-acre agricultural research service watershed west of Albuquerque, New Mexico, using the Wilcoxon's rank sum test. Various levels of statistical significance are discussed, and shown graphically, to conclude conclusively that antecedent rainfall influences runoff from a semiarid watershed.

From the Proceedings of the 1973 Meetings of the Arizona Section - American Water Resources Assn. and the Hydrology Section - Arizona Academy of Science - May 4-5, 1973, Tucson, Arizona / An infiltration- wetting agent study, using the wetting agent "WATER-IN", was conducted in the ponderosa pine forest type of east central Arizona. An application rate of 10 gallons of wetting agent per acre was used on bare mineral soil and on ponderosa pine litter. The infiltration rate was measured by a modified North Fork infiltrometer. It was found that "WATER-IN" significantly increased water runoff when applied to litter, but, when applied to bare mineral soil, "WATER-IN" caused a significant increase in water infiltration. The wetting agent did not significantly affect antecedent moisture, soil particle distribution, litter water holding capacity, or litter bulk density. It is presently hypothesized that the increase in water infiltration on treated bare mineral soil is due to a decrease in the average bulk density of the surface inch of soil. The increase in runoff when litter is treated is probably due to an interaction, either physical, chemical, or both, between the humus layer and "WATER-IN ", creating a hydrophobic condition where one did not exist before.