Hydrological regionalization of maximum stream flows using an approach based on L-moments

Abstract

The proper design of hydraulic structures depends on estimates of maximum stream flows. The scarce stream flow monitoring in Brazil has led to the use of regionalization methods. The main objective of this study was to develop a tool via regional function to estimate maximum stream flows and their corresponding return periods (RP) with the aid of techniques based on the L-moments method, seeking for adequate hydrologic engineering applications and flood risk management. Annual maximum stream flow historical series were adjusted to traditional 2-parameter probability density functions (PDFs) (Normal, 2-parameter Log-Normal, Gumbel, Gamma) and multiparameter PDFs (GEV and Kappa), based on the L-moments method, which were used in the development of the regional function employing the dimensionless curve method. The regional function's predictive capability was determined by cross-validation for different RPs. It can be concluded that the approach based on L-moments was successfully used to adjust the regional function. In addition, the regional function: i) was improved when using the aforementioned multiparameter PDFs and ii) was framed as optimum for RP of up to 100 years and considered useful for practical engineering projects and flood risk management.Keywords: Flood risk management; Statistical hydrology; GEV; Kappa; Mirim-São Gonçalo transboundary basin. RESUMOO dimensionamento adequado de estruturas hidráulicas é dependente das estimativas de vazões máximas. A escassez no monitoramento hidrológico no Brasil tem levado ao uso de métodos de regionalização. O principal objetivo do presente estudo foi desenvolver uma ferramenta via função regional para a estimativa das vazões máximas e seus respectivos tempos de retorno, com o suporte de técnicas baseadas no método dos momentos-L, com vistas a aplicações adequadas da engenharia hidrológica e da gestão de risco de cheias. As séries de vazão máxima diária anual foram ajustadas às funções densidade de probabilidade tradicionais de 2 parâmetros (Normal, 2-parameter Log-Normal, Gumbel, Gamma) e multiparâmetros (GEV and Kappa), baseando-se no método dos momentos-L, as quais foram utilizadas no desenvolvimento da função regional pelo método da curva adimensional. A capacidade preditiva da função regional foi determinada por validação cruzada para diferentes tempos de retorno. Pode-se concluir que a abordagem baseada nos momentos-L no ajuste da função regional foi satisfatória. Além disso,a função regional: i) foi aperfeiçoada quando as distribuições multiparâmetros acima mencionadas foram usadas e ii) foi classificada como ótima para tempos de retorno de até 100 anos sendo útil a projetos práticos de engenharia e na gestão de cheias.

Regional flood frequency analysis using L‐moments for geographically defined regions: An assessment in Brazil

“…The nonstationarity of hydrological data is one of the most relevant concerns when analysing historical series. Recently, many authors have addressed the necessity of using a reliable nonparametric stationarity test before further considerations (Beskow, Mello, et al, ; Cassalho et al, ; Zhang, Gu, Singh, Xiao, & Xu, ). Among them, the stationarity test of Mann–Kendall is the most frequently used (Wang, Li, Feng, & Hu, ).…”

“…In South America, there is no evidence of a complete RFFA derived from the index‐flood method with basis on L‐moments. However, similar to Australia, a few authors have used some principles proposed by Hosking and Wallis () in their hydrological frequency analysis, for example, discordancy measure ( D i ), heterogeneity measure ( H ) and L‐moments (Beskow et al, ; Beskow, Mello, et al, ; Cassalho et al, ).…”

“…Hosking and Wallis () present five different approaches for forming regions: by geographical convenience, subjective partitioning, objective partitioning, cluster analysis, and multivariate methods. Regional studies considering the geographical convenience criteria can be found in Brazil (Cassalho et al, ) and Turkey (Aydoğan et al, ), whereas those defined from clustering techniques were developed by Noto and La Loggia () and Saf () for Italy and Turkey, respectively.…”

Regionalization of reference streamflows for the Araguaia River basin in Brazil

“…However, caution should be exercised regarding its use because on one hand, for hydraulic works, there is the possibility of overestimation, which can lead to unnecessary construction costs. On the other hand, there is the risk of underestimation, which puts the integrity of the hydraulic work at risk (Cassalho et al, 2017b). The same concern applies to the minimum streamflows: overestimation will result in assigning a greater volume than the capacity of the water body, which may lead to conflicts, while underestimation may lead to non-optimal use.…”

“…Several studies have been conducted that use different distributions (Ahn & Palmer, 2016;Basu & Srinivas, 2015;Cassalho, Beskow, Mello, & Moura, 2018). Thanks to computational advances, 4 or 5-parameter distributions are now being used (Cassalho et al, 2017b;Kjeldsen, Ahn, & Prosdocimi, 2017) and should be preferred whenever possible.…”