Areal Reduction Factors from Rain Movement

Bengtsson, Lars; Niemczynowicz, Janusz

doi:10.2166/nh.1986.0005

Cited by 22 publications

(14 citation statements)

References 8 publications

(11 reference statements)

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“…The analytical methods (correlation by Rodriguez-Iturbe and Mejía 1974, Sivapalan and Blöschl 1998and Omolayo 1989; crossing properties by Bacchi and Ranzi 1996; scaling methods by de Michele et al 2001 andLangousis 2005; and storm movement by Bengtsson and Niemczynowicz 1986) attempt to put areal reduction factor (ARF) estimation on a sounder scientific basis. However, they are generally based on assumptions that are not entirely true descriptions of the real rainfall process, which is a cause for concern and uncertainty regarding the results.…”

Section: Discussion and Recommendationsmentioning

confidence: 99%

“…In contrast to previous methods which were empirically or statistically based, Bengtsson and Niemczynowicz (1986) take a simplified conceptual physics approach to ARF estimation by moving an idealised storm across an area. The resulting ARFs should therefore be more similar to ARFs derived using storm-centred rather than fixed-area approaches.…”

Section: Storm Movementmentioning

confidence: 99%

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Review of methods for deriving areal reduction factors

Svensson¹,

Jones²

2010

J Flood Risk Management

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The NERC and CEH trade marks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. The design of hydraulic structures requires knowledge of how much rain is likely to fall within a certain amount of time, and over a specific area. Point rainfalls are only representative for a very limited area, and for larger areas the areal average rainfall depth is likely to be much smaller than at the point of maximum observed depth. The estimation of areal reduction factors (ARFs) is concerned with the relationship between the point and areal rainfalls. This relationship has been found to vary with, for example, predominant weather type, season and return period. Traditionally, ARF estimates are based on empirical methods though, more recently, a range of analytical methods have been applied. The review has found that no method is unambiguously correct. However, the traditional data-intensive, empirical, fixed-area methods still have advantages, including probabilistically correct ARF estimates and applicability over a comprehensive range of spatial and temporal scales. Although the analytical techniques try to put ARF estimation on a sounder scientific basis, they tend to rely on simplified assumptions and/or are only applicable within limited scales. The use of radar is problematic because of inhomogeneities and short data records, as well as possible biases in the ARF estimates.

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Section: Discussion and Recommendationsmentioning

confidence: 99%

Section: Storm Movementmentioning

confidence: 99%

Review of methods for deriving areal reduction factors

Svensson¹,

Jones²

2010

J Flood Risk Management

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“…An increase of rainfall intensity would influence the operation of a sewerage system to a higher degree than an increase of duration. There is some evidence that convective raincells have similar areal extension in different climatic conditions (Bengtsson & Niemczynowicz, 1986), although rainfall volumes given by single raincells seem, however, to increase in a warmer climate. This means that, assuming that cloud velocity remains unchanged when climate changes, an increase of rainfall volumes is obtained by an increase of intensities while point-durations remain unchanged.…”

Section: Possible Changes In Rainfall Inputmentioning

confidence: 99%

Impact of the greenhouse effect on sewerage systems—Lund case study

Niemczynowicz

1989

Hydrological Sciences Journal

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The possible impacts of modifications in rainfall patterns due to the greenhouse effect on the function of a sewerage system are studied based on a case study of the city of Lund, Sweden. The Storm Water Management Model is used to simulate changes in the runoff pattern. The paper lists the possible effects of increases in rainfall intensity on the urban water cycle, quantifies changes in the runoff pattern, and discusses the significance of detected changes in terms of economic and environmental consequences and the possibilities to undertake preventative measures. For the purpose of the present study, 10%, 20% and 30% levels of rainfall increase were assumed. In spite of considerable uncertainty regarding the potential future rate of hydrological changes, the examples given of possible impacts of the greenhouse effect on the function of the sewerage system bear witness to the great vulnerability of sewerage systems to the results of climate changes. Consequences de l'effet de serre sur les systèmes d'égouts étude de cas à LundRésumé Les impacts possibles sur les systèmes d'égouts des modifications des précipitations dues à l'effet de serre ont été étudiées en tant qu'étude de cas dans la ville de Lund. A cet effet, a été utilisé un programme d'ordinateur "The Storm Water Management Model" afin de simuler les modifications de chûtes de pluie. L'étude analyse les effets possibles sur le cycle des eaux urbaines, en augmentant l'intensité des précipitations et le diagramme des intensités des pluies, et discute l'importance de la détection des changements dans un contexte économique et des conséquences sur l'environnement. Pour cet objectif, le niveau des précipitations a été augmenté de 10%, 20% et 30%. Bien que l'on ne soit pas très fixé sur le taux potentiel futur des changements hydrologiques, les exemples retenus, en considération de l'effet de serre sur les systèmes d'égouts, montrent que les changements climatiques rendent les systèmes d'égouts très vulnérables.

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“…Empirical fixed-area methods (Myers and Zehr, 1980;NERC, 1975;Omolayo, 1993;Shaw et al, 2011) are computationally intensive but applicable over a comprehensive range of spatial and temporal scales. In contrast, analytical methods (Bacchi and Ranzi, 1996;Bengtsson and Niemczynowicz, 1986;Rodriguez-Iturbe and Mejía, 1974;Veneziano and Langousis, 2005) require less computation but are only applicable within limited scales as they often rely on simplified assumptions. Rodriguez-Iturbe and Mejía (1974) ARFs using the correlation between two gauges, which was assumed to follow either an exponentially decaying distribution or a Bessel-type correlation structure.…”

Section: Introductionmentioning

confidence: 99%

“…This method also assumed that the point rainfall was isotropic and Gaussian distributed with a zero mean. Bengtsson and Niemczynowicz (1986) deduced ARFs from the movement of convective storms by assuming that the rainfall intensity distribution transverse to the storm was exponential. Bacchi and Ranzi (1996) derived ARFs using a stochastic method based on the assumptions that the number of crossings of high rainfall intensity levels was Poisson distributed and that the process of crossings was stationary and independent of events.…”

Section: Introductionmentioning

confidence: 99%