Multivariate Frequency Analysis of Annual Maxima Suspended Sediment Concentrations and Floods in the Jinsha River, China

Abstract. Most of the hydrological and hydraulic studies refer to the notion of a return period to quantify design variables. When dealing with multiple design variables, the well-known univariate statistical analysis is no longer satisfactory and several issues challenge the practitioner. How should one incorporate the dependence between variables? How should the joint return period be defined and applied? In this study, an overview of the state-of-the-art for defining joint return periods is given. The construction of multivariate distribution functions is done through the use of copulas, given their practicality in multivariate frequency analysis and their ability to model numerous types of dependence structures in a flexible way. A case study focusing on the selection of design hydrograph characteristics is presented and the design values of a three-dimensional phenomenon composed of peak discharge, volume and duration are derived. Joint return period methods based on regression analysis, bivariate conditional distributions, bivariate joint distributions, and Kendal distribution functions are investigated and compared highlighting theoretical and practical issues of multivariate frequency analysis. Also an ensemble-based method is introduced. For a given design return period, the method chosen clearly affects the calculated design event. Eventually, light is shed on the practical implications of a chosen method.

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Curvas-chave de descargas de sedimentos em suspensão no Baixo São Francisco

Revista Brasileira de Geografia Física ◽

10.26848/rbgf.v13.3.p1248-1262 ◽

2020 ◽

Vol 13 (3) ◽

pp. 1248 ◽

Cited By ~ 1

Author(s):

Solange Cavalcanti de Melo ◽

José Coelho de Araújo Filho ◽

Renata Maria Caminha Mendes de Oliveira Carvalho

Keyword(s):

Suspended Sediment ◽

Suspended Sediment Concentration ◽

Suspended Sediments ◽

Sediment Concentration ◽

Gradual Reduction ◽

Sao Francisco River ◽

Sediment Loads ◽

São Francisco River ◽

Historical Series ◽

Suspended Sediment Concentrations

RESUMOO conhecimento da análise quantitativa das concentrações de sedimentos em suspensão transportados pelo rio São Francisco bem como sua relação com as vazões é de muita importância, pois pode auxiliar na identificação dos efeitos da intervenção humana e ou ocasionados pelas condições naturais da região. As regiões a jusante dos barramentos no rio São Francisco apresentam como principal consequência a regularização das vazões e a diminuição das concentrações de sedimentos. O objetivo da pesquisa foi determinar as curvas-chave de sedimentos em suspensão (CCS) nas estações fluviométricas instaladas no Baixo São Francisco (BSF) após a barragem de Xingó. Para o estabelecimento dessas curvas foram utilizados dados de vazão e concentração de sedimentos em suspensão, obtidos do sistema Hidroweb no site da Agência Nacional da Água (ANA) no período de 1999 a 2018. Foram obtidas CCS para todo o trecho do BSF as quais apresentaram bons coeficientes de determinação. Na análise dos dados também foi possível perceber que nos últimos anos, desde 2013 houve redução gradativa das vazões disponibilizadas na barragem de Xingó. Consequentemente, houve também a redução gradativa das cargas de sedimentos em suspensão geradas nas estações de Piranhas, Traipu e Propriá, ou seja, os menores valores já registrados no BSF correspondendo as menores séries históricas tanto de vazão como de sedimentos em suspensão. Keys curves of sediment discharges in suspension in the Lower São Francisco A B S T R A C TThe knowledge of the quantitative analysis of suspended sediment concentrations carried by the São Francisco River as well as its relation with the flows is of great importance, since it can help in the identification of the effects of human intervention and/or caused by the natural conditions of the region. In the downstream regions of the São Francisco riverbanks, the main consequence was the regularization of flow rates and the reduction of sediment concentrations. The objective of the research was to determine the key curves of suspended sediments (CCS) at the fluviometric stations installed in the lower São Francisco river after Xingó dam. For the evaluation, flow data and suspended sediment concentration were used. These data were obtained from the Hidroweb system on the website of the National Water Agency (ANA) from 1999 to 2018. CCS were plotted for all stretches and presented good coefficients of determination (R2). Based on the analysis of the data it was also possible to notice that in recent years, since 2013 there has been a gradual reduction of the flows available in the Xingó dam. Consequently, there was also a gradual reduction of suspended sediment loads generated at the Piranhas, Traipu and Propriá stations, that is, the lowest values already recorded in lower São Francisco, corresponding to the lower historical series of both discharge and suspended sediments.Keywords: dam, flow, sediments

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Dynamics of suspended sediment load in the upper part of the Rasina River Basin in 2010

Glasnik srpskog geografskog drustva ◽

10.2298/gsgd1304023m ◽

2013 ◽

Vol 93 (4) ◽

pp. 23-40

Author(s):

Sanja Mustafic ◽

Predrag Manojlovic ◽

Predrag Kostic

Keyword(s):

Suspended Sediment ◽

River Basin ◽

Sediment Load ◽

Suspended Sediment Load ◽

Spring Season ◽

Autumn Season ◽

Specific Transport ◽

Suspended Sediment Concentrations ◽

Load Transport

The paper treats the issue of the suspended sediment load transport in the upper part of the Rasina River Basin, upstream from the "Celije" reservoir during the year of 2010. Measurements of the suspended sediment concentrations were being done at two hydrological profiles Brus and Ravni. Total quantity of the suspended sediment load that was transported at the profile of Brus in 2010 amounted to 3,437.3 t, which gave the specific transport of 16.4 t/km2/year. At the downstream profile of Ravni, 43,165 t of the suspended sediment load was transported, that is, 95.7 t/km2/year. The basin on the whole is characterized by the existence of two seasons, which by their characteristics in the load transport represent the extreme variants. During the winter-spring season, 74-85.8 % of the total annual load was transported, ?nd during the summer-autumn season between 14.2 and 26 %.

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