Multiple rainfall event pollution transport by sustainable drainage systems: the fate of fine sediment pollution

S. Arthur,H. Haynes,V. Olive,D. Allen

doi:10.1007/s13762-016-1177-y

Abstract

A key design criterion of sustainable urban drainage systems is to mitigate urban stormwater pollution. Current research defines sustainable urban drainage systems (SuDS) pollutant treatment efficiency through the detention of total suspended solids, urban nutrients and heavy metal pollutants within the system during a design flow event, with research focusing on sand (>2 mm) sediment movement. The impact of multiple rainfall–runoff events on the fine sediment (<2 mm) treatment efficiency of SuDS is not yet well defined, and the temporal movement of detained sediment has not been investigated in detail. The field research presented in this paper addresses this research gap, monitoring ongoing fine sediment transport through a best-practice-designed SuDS network over 12 months through the use of a novel rare earth oxide trace methodology. Through time-stepped monitoring of the fine sediment pollution across three SuDS treatment trains (networks), the following key conclusions have been drawn. (1) That fine sediment becomes re-suspended and re-deposited within SuDS assets and the network as a result of ongoing multiple rainfall–runoff events. (2) That this re-suspension continues for over 52 weeks. (3) That by area, linear wetlands (within the monitored networks) outperform wetland and swale assets in multiple event fine sediment detention. And (4) that multiple event monitoring and analysis of fine sediment within a SuDS network highlights the under-performance of SuDS assets against current design event expectations.

Highlights

Sustainable urban drainage systems (SuDS) have been implemented within urban development environs to convey and treat urban stormwater (Woods-Ballard et al 2007)
The field research presented in this paper addresses this research gap, monitoring ongoing fine sediment transport through a best-practice-designed sustainable urban drainage systems (SuDS) network over 12 months through the use of a novel rare earth oxide trace methodology
Equation 2 provides an insight into the key drivers of fine sediment resuspension and deposition within this SuDS network, connecting the single release tagged sediment movement to flow and runoff event characteristics

Summary

Introduction

Sustainable urban drainage systems (SuDS) have been implemented within urban development environs to convey and treat urban stormwater (Woods-Ballard et al 2007). Urban development creates impervious spaces that prevent infiltration of stormwater runoff into the soil, thereby increasing the runoff into downstream watercourses. The use of land for urban purposes, residential living, commercial development and industrial business, creates a concentration of heavy metal and sediment pollutants that are collected from urban impervious surfaces and conveyed into neighbouring watercourses by the stormwater flow (Sekabira et al 2010). Understanding long-term sediment conveyance–detention processes in sustainable urban drainage systems (SuDS) is key to quantifying the contaminant risk and potential flood storage loss within the urban environment drainage network. The long-term functionality of ephemeral SuDS assets or blue–green treatment trains is not well understood

Methods

Results

Conclusion