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According to the literature, various definitions of groundwater exist. For some au­thors, groundwater is defined as water only in those pores that are completely saturated, but for others a more general definition is acceptable with the ground­water being all the water below the ground surface either in the saturated or in the unsaturated part. A […]

For a better understanding of the qualitative and quantitative relationships between water and roads, the general interaction of road to water should first be established. The approach adopted here for this interaction analysis is by considering the water balance. The relation between a road and water can be defined in system theory terms where input […]

SigurOur Erlingsson[3], Mihael Brencic and Andrew Dawson Abstract This chapter describes the relation between road structures and water giving the general water balance equation for the pavement structure. Aquifers are briefly introduced. The pavement and its associated embankment are divided into the saturated zone and the unsaturated zone. Porous media are also described briefly together […]

Pavement sub-surface drainage lies at the boundary of several disciplines each hav­ing their own special terms and notations. The book does not avoid these but, rather, seeks to define them when they are used. To help readers, a “Glossary” is included (Annex C) as well as a list of terms in several languages (Annex B) […]

1.12.1 National and Trans-National The demands of legislation can greatly influence the design and management of a road in order to control its influence on the water environment. General legislation, such as European directives (e. g. the Water Framework Directive), define water pro­tection in a general manner with universal requirements that no pollutant input is […]

The ultimate reason for having drainage is because of rain! Therefore the drainage needs and solutions will be heavily influenced by the climate where the road is built. Broadly, climate may be divided by temperature and by rain/snowfall. Typically climatologists further differentiate on temperature variation across the year and on rainfall distribution. A very commonly […]

Drainage systems come in many shapes and forms (see Chapter 13) but they also share many common features — they are placed lower than the section of road or earthworks they are intended to drain and they comprise materials (and/or pipes) that are more permeable than the surrounding materials. Broadly, they may be classified as […]

Runoff derives, principally, from rainfall falling on the pavement and surround­ing ground. Although surface water drainage falls outside the scope of this book, runoff becomes of interest as some soaks in through cracks or through pervious surfacings. The proportion soaking-in will vary depending on the rainfall pattern, road surface quality and the permeability of the […]

Pore suctions have the effect of “pulling” the saturated zone nearer the ground surface than it would otherwise have been from where evaporation becomes pos­sible. When evaporation is significant then upward water flow takes place to re­place the water being evaporated. Evapotranspiration by vegetation also introduces an upward water flow towards roots in a similar […]