Sensitivity Analysis of a Riparian Vegetation Growth Model

Michael Nones,Arianna Varrani

doi:10.3390/environments3040030

Michael Nones, Arianna Varrani

Open Access

https://doi.org/10.3390/environments3040030

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Abstract

The paper presents a sensitivity analysis of two main parameters used in a mathematic model able to evaluate the effects of changing hydrology on the growth of riparian vegetation along rivers and its effects on the cross-section width. Due to a lack of data in existing literature, in a past study the schematization proposed here was applied only to two large rivers, assuming steady conditions for the vegetational carrying capacity and coupling the vegetal model with a 1D description of the river morphology. In this paper, the limitation set by steady conditions is overcome, imposing the vegetational evolution dependent upon the initial plant population and the growth rate, which represents the potential growth of the overall vegetation along the watercourse. The sensitivity analysis shows that, regardless of the initial population density, the growth rate can be considered the main parameter defining the development of riparian vegetation, but it results site-specific effects, with significant differences for large and small rivers. Despite the numerous simplifications adopted and the small database analyzed, the comparison between measured and computed river widths shows a quite good capability of the model in representing the typical interactions between riparian vegetation and water flow occurring along watercourses. After a thorough calibration, the relatively simple structure of the code permits further developments and applications to a wide range of alluvial rivers.

Highlights

In the last few decades, many studies have analyzed the morphological evolution of alluvial watercourses affected by anthropogenic disturbances, highlighting that changes occur along the stream, and across it, influencing both bed morphology and riparian vegetation at the local scale [1,2,3]
The sensitivity analysis reported here has been performed by changing the values of initial population P0 and growth rate r of the riparian vegetation, in accordance with available evidence in population P0 and growth rate r of the riparian vegetation, in accordance with available evidence in the the established literature [59,60], which is, not exhaustive in addressing these established literature [59,60], which is, not exhaustive in addressing these parameters to parameters to date
Because the main model is to reproduce the active width of alluvial watercourses, the results report the comparison aim of the model is to reproduce the active width of alluvial watercourses, the results report the between measured and computed active river widths, derived from the above reported model

Summary

Introduction

In the last few decades, many studies have analyzed the morphological evolution of alluvial watercourses affected by anthropogenic disturbances, highlighting that changes occur along the stream, and across it, influencing both bed morphology and riparian vegetation at the local scale [1,2,3]. Following these observations, various works argue that hydrology, morphology, and riparian plants represent three mutually inter-dependent components of the riverine environment [4], requiring an interdisciplinary approach at various scales, which is yet to be comprehensively established. As a result, numerical models can be quite hard to manage under the engineering and computing points of view, especially in the Environments 2016, 3, 30; doi:10.3390/environments3040030 www.mdpi.com/journal/environments

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Conclusion