Vegetated Permeable Pavement Systems

Vegetated Permeable Pavement Systems: Evaluation of the hydrologic behaviour to improve climate-adaptive design

Gravenberch, Jip (TU Delft Civil Engineering and Geosciences)

Delft University of Technology

Water Management | Urban Water Engineering

2022-01-21

Vegetated permeable pavement systems (VPPS) contribute to a more climate-resilient application of urban water management. However, a complete hydrologic evaluation of vegetated permeable pavement systems has not been found in existing literature. This research presents an evaluation of the hydrologic performance of VPPS under Dutch climatic conditions is using a combination of a literature study, field evaluation in controlled and uncontrolled environments, and modelling in Hydrus-1D, a software that is designed for analysis of one-dimensional water flow in variably saturated porous media.
At first, the key processes and the potential influence on vegetated infiltration behaviour were identified in the literature study. The hydrologic performance is quantified by two main indicators: the infiltration rate and the water storage capacity, and influenced by changing soil hydraulic properties. Subsequently, the soil hydraulic properties are influenced by processes and factors (clogging, soil compaction, root content, organic matter, biological activity, and soil moisture content).
In the field evaluation, the surface infiltration rates and soil moisture content of two VPPS (with differing amount of grass) and one bare-soiled reference plot were measured using, the Full Scale Infiltration Test (FSIT). Infiltration rates were determined during the tests whil ethe soil moisture content was monitored continuously.
The field tests have led to a number of key findings. It was found that the presence of vegetation compared to no vegetation has a positive effect on the infiltration rate. Moreover, increased vegetation resulted in higher surface infiltration rates, as the soil structure was better maintained against soil compaction due to fast wetting. A possible reason is the increased grass content, which indicates higher root content, and potentially increased organic matter content and biological activity. Another important finding is that fitting the measured water depth curves of the vegetated plots can be calibrated to the Horton infiltration model. The model of Horton shows the dependency of infiltration rate to soil moisture content and water depth. The Full-Scale Infiltration Method is therefore a viable tool to determine infiltration rates and predict infiltration behaviour at the surface.

Although the model was able to make a representation of the observed dynamic water content, the fitted soil hydraulic parameters were very unrealistic compared to common measured values. Efforts to estimate more realistic parameters resulted in numerical divergence. Moreover, soil matric potential data was missing in this study to obtain the soil moisture retention and hydraulic conductivity curve..
Even though the modelling effort did not succeed in this research, it is expected that HYDRUS-1D can be a useful tool to predict soil moisture behaviour provided that rainfall data is used as input over a longer time period, including soil moisture and matric potential measurements.

A base is created to start further research in the evaluation of VPPS hydrologic performance. This research obtained the initial results after construction. In further research, the long-term hydrologic effects of these systems can be investigated. As the experimental set-up at the Green Village is readily available, it is possible to immediately start monitoring soil moisture content and rainfall in the long term.

vegetated
permeable
pavement
systems
infiltration
SUDS

http://resolver.tudelft.nl/uuid:087ac5d8-322a-4e51-ae71-495c5ed746b0

Student theses

master thesis

© 2022 Jip Gravenberch