Modelling of Gully Erosion Site Data in Southeastern Nigeria, Using Poisson and Negative Binomial Regression Models

Ngozi Levi Nwakwasi

doi:10.11648/j.jccee.20180304.13

Abstract

The development of gully and other forms of erosion have become the greatest environmental problem facing the people of Southeastern Nigeria. The availability of farm land for agricultural production and construction activities have, been greatly reduced due to soil erosion. This study is set to apply Poisson and negative binomial regression models to identify the major factors that contribute to gully erosion development in Southeastern Nigeria and to ascertain better model suitable for prediction of gully erosion, using secondary data. Maximum likelihood estimation procedure was used to estimate the parameter of the selected model with the number of gully erosion sites as the response variable (Y) and 5-explanatory variable (X’s). Also applying the forward selection criteria to the 5-explanatory variables, model 5 is best suitable for forecasting the subject under study. The result of the Poisson regression model showed that there was over dispersion in gully erosion site data since the dispersion parameter (3.677) was greater than 1 hence underestimating the standard error and over estimating the coefficient of the explanatory variable, consequently giving misleading inference. The result of the assessment criteria for Poisson regression model and Negative binomial regression model revealed that the Negative binomial regression model predicts gully erosion soil data better in southeastern Nigeria as considered in this study. Heavy Rainfall (HRF), Extractive Industries (EXI), Excess Farm activities (EFX) are the major contributors to gully erosion site development in southeastern Nigeria, with Heavy Rainfall ranking first. A model suitable for prediction of gully erosion sites in southeastern Nigeria has been developed.

Highlights

Soil erosion is considered to be a major environmental problem since it seriously threatens natural resources and the environment [1]
The objective of this study is to provide a model which will be able to predict the major contributors of gully erosion site in southeastern Nigeria
The Generalized Linear Model (GLM) with Poisson as the fundamental distribution for modelling a count data using the Log link function and the Negative Binomial distribution was latter employed to correct the error of over dispersion in the count data in situation where the result of the Poisson regression model shows over dispersion

Summary

Introduction

Soil erosion is considered to be a major environmental problem since it seriously threatens natural resources and the environment [1]. Soil loss by runoff is a severe ecological problem occupying 56% of the worldwide area and is accelerated by human induced soil degradation [2]. Soil erosion is a serious environmental, economic and social problem which causes severe land degradation and soil productivity loss and threaten the stability and health of society in general and sustainable development of rural areas in particular[3]. The menace of soil erosion especially gully in no doubt represents a major ecological challenge facing most states in Nigeria especially Anambra, Imo, Ebonyi, Abia and other states in the humid tropical regions of southern Nigeria [4]. Erosion have become one of the greatest environmental disasters facing many towns and villages in Southeastern Nigeria [7, 8]

Objectives

Methods

Results

Conclusion