Statistical Modelling of Significant Wave Height: Inshore and Offshore Bonny River Estuary, Nigeria

Abstract

The selection of best – fit probability distribution is of fundamental importance in the design, planning, and operability studies for harbours, coastal and offshore structures and exploitation of coastal resources. A wrong choice of probability distribution could lead to either under – or over – estimation of design loads, which may have detrimental impacts on safety and  project economy. Consequently the Inshore and Offshore wave data of Bonny River estuary, Nigeria was studied by fitting Rayleigh, 2- parameter Lognormal, Fisher – Tippett Type 1(FT-1), 2-parameter and 3-parameter Weibull probability distributions using probability paper method. The probability distributions were subjected to five model evaluation metrics; coefficient of determination (R²), demeaned RMSE, normalizedRMSE, Scatter index (SI) and Performance scores index(d₁) and a scoring scheme was adopted on the basis of which the best – fit probability distribution for either Inshore of Offshore was selected. The results show that 2-parameter Lognormal distribution is the best –fit probability distribution for the Inshore station, seconded closely by Fisher – Tippett Type 1 and 3- parameter Weibull distributions. The results also show that Fisher – Tippett Type 1 is the best – fit probability distribution for the offshore station seconded closely by 3 – parameter Weibull distribution. This study will contribute to the development of the coastal zone and also a recipe for Integrated Coastal Zone Management of the Nigerian Gulf of Guinea.

Key words: Bonny river estuary, goodness of fit tests, integrated coastal  zone management,  significant wave height,  probability distribution models.

DOI: 10.7176/CER/11-4-08

Publication date:May 31^st 2019