Urban River Water Level Increase Through Plastic Waste Accumulation at a Rack Structure

Dorien Honingh,Nick Van De Giesen,Olivier Hoes,Wim Uijttewaal,Tim Van Emmerik,Hadi Kardhana

doi:10.3389/feart.2020.00028

Abstract

Plastic debris in water systems is a major challenge for our ecosystem, because it is extremely persistent in the environment. Apart from the importance of reducing the amount of plastic entering the ocean, clearing the rivers from debris is important for societal concerns, such as flood risks. Plastic waste accumulation at trash racks leads to a rise in upstream water level and may increase urban flood risk. Until now, most studies of riverine debris accumulation predominantly focused on organic accumulations at trash racks and bridge piers. In this study, flume experiments were used to study the behavior of plastic and mixed debris accumulations. One of the key findings from this study is that plastic debris causes a faster blockage than organic matter, as the plastic blockage contains fewer voids and therefore has a higher blockage density. In addition to the flume experiments, field measurements were performed in the Cikapundung River (Indonesia). This river is one of the tributaries of the Citarum River, which is considered one of the world’s most heavily polluted rivers. Combining the results of the flume experiments and field measurements demonstrated that a backwater rise of 1 m/h is plausible for a blocked trash rack in the Cikapundung River, illustrating the additional flood risk caused by plastic pollution. Our results emphasize the need for further quantifying riverine (plastic) debris and investigating its relation to changes in the water system behavior, including its influence on urban flood risk.

Highlights

Plastic pollution in aquatic environments is an emerging hazard because of its direct and indirect negative effects on ecosystem health and human livelihood
Plastic debris blocks the trash rack faster compared to organic debris (Figure 3), which results in a faster water level rise behind the trash rack
The mixed debris shows comparable results to plastic debris at the start of the test, since a fast blockage was observed combined with fast-initial water level increase

Summary

Introduction

Plastic pollution in aquatic environments is an emerging hazard because of its direct and indirect negative effects on ecosystem health and human livelihood (van Emmerik and Schwarz, 2020). Plastic Increases Urban Water Level into microplastics (Weinstein et al, 2016) and negative impacts on mangrove forests (Ivar do Sul et al, 2014). Once in the water system, plastic pollution accumulates at hydraulic infrastructures (such as rack structures), leading to clogging of the urban drainage system. This may lead to increased flood risk in urban areas (Njeru, 2006; Windsor et al, 2019). We aim to shed additional light on the relation between the abundance of plastic debris in rivers and increased flood risk, by estimating the water level increase in response of plastic waste accumulation in the Cikapundung River, Indonesia

Objectives

Methods

Results

Conclusion