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The reactivation of Warsaw oxbow lakes as a leitmotiv of urban design

Solarek Krystyna

Journal of Water and Land Development

2020

no. 45

165--170

Oxbow lakes occurring in floodplains are those natural elements that are subject to rapid changes, which may lead to their disappearance. These are extremely valuable ecosystems and landscape components, as well as water management units. However, they quickly disappear if they are not periodically fed with river water, which takes place especially when rivers are embanked. Such a situation occurs, among others in Warsaw, in the Vistula valley. There are many opportunities for the reactivation of oxbow lakes, including through technical activities. It is not always possible to restore the natural values of the valley in urbanized areas, however, oxbow lakes can then also play a recreational role and they can fulfill an important task in improving the quality of life, being also an important element of the public space system. The author has carried out research related to land development projects of the new district located in the Vistula River valley in Warsaw (the Siekierkowski Arc). Many different design solutions have been proposed, taking as a leitmotiv the restoration of oxbow lakes, for example: (1) reconstruction of the water channel in the former watercourse with the boulevard along its fragment and with the public park in another part, (2) water supplying of the existing oxbow lake through the green and blue infrastructure system. The author presents few urban designs carried out under her direction for this area and shows that creative reactivation of oxbow lakes can improve water conditions, and be beneficial for the introduction of a new, attractive development.

Regional frequency analysis of extreme precipitation in northeastern Algeria

Dad S., Benabdesselam T.

Journal of Water and Land Development

2018

no. 39

27--37

The aim of the study is to improve the quality of estimating of the annual maximum daily precipitations of the northeastern area of Algeria. The regional frequency analysis based on L-moments was used. The investigated area is represented by 58 measuring stations. The main stages of the study were the definition of homogeneous regions and the identification of the regional distribution. It has been defined that the study region is homogeneous in terms of L-moments ratios despite the climatic differences within the region. Among the different tested distributions; the generalised extreme value (GEV) distribution has been identified as the most appropriate regional distribution for modelling precipitation in the region. The growth curve, derived from the regional distribution, was established. Therefore, to estimate the different return period’s precipitation quantiles in a given site of the region, the mean precipitation of the site has to be multiplied by the corresponding regional quantile (growth factor). Comparison of the quantiles estimated from the regional and at-site frequency analysis showed that in the majority of stations (82.8%) at-site model underestimates the quantiles having high return periods.

Celem pracy była poprawa jakości ocen maksymalnego w ciągu roku dobowego opadu na obszarze północno-wschodniej Algierii. Wykorzystano statystykę L-momentów do analizy częstotliwości regionalnej. Badany obszar jest reprezentowany przez 58 stacji pomiarowych. Głównymi etapami badania było zdefiniowanie regionów homogenicznych i identyfikacja rozkładu regionalnego. Stwierdzono, że badany region jest homogeniczny w znaczeniu proporcji momentów L, mimo różnic klimatycznych w obrębie regionu. Spośród testowanych rozkładów najbardziej odpowiedni do modelowania opadu w regionie okazał się uogólniony rozkład wartości ekstremalnych (GEV). Ustalono krzywą wzrostu wyprowadzoną z rozkładu regionalnego. Aby oszacować kwantyle okresów powtarzalności opadów dla danego stanowiska w regionie, średni opad w tym stanowisku należy pomnożyć przez odpowiedni kwantyl regionalny (czynnik wzrostu). Porównanie analizy częstotliwości w odniesieniu do regionu i stanowiska wykazało, że w większości stacji (82,8%) model stanowiskowy obniża wyniki oszacowania kwantyli o długim okresie powtarzalności.