Introduction:
This essay will focus on the application of open-joined paving blocks to minimize the impact of urban development on natural drainage system-capturing, slowing and absorbing storm water in the urban condition. In the natural system, 10% surface flow,30% evapotranspiration, 40% infiltration, 20% interflow, while in an urban condition, 75% surface flow to pipes, 15% evapotranspiration, 5% infiltration, 5% interflow1. The unbalanced water distribution when water comes to the ground causing severe problems as flooding and erosion, destroying natural habitat and insufficient fill-in of water table.
Porous pavement could increase the infiltration rate and interflow rate and reduce the overwhelmingly high rate of surface flow. Porous pavement materials include: porous aggrregate, porous turf, plastic geocells, open-joined paving blocks, open-celled paving grids, porous concrete, porous asphalt. Open-joined paving blocks is one of the most commonly used.
Open-jointed paving: open-jointed paving blocks are solid units shaped or placed to leave open space in the joins between adjacent units. The blocks are manufactures from concrete, clay or from natural stones or wood. The joins are filled with porous aggregate or vegetated soil. Together, the blocks and joins form a composite surface that can be porous and permeable while bearing traffic loads though the structure.
Techniques
What does porous pavement system do and not do?
Pervious paving allows rainwater to either pass through the paving system itself or through joint openings between pavers.2 They are designed to capturing, slowing and absorbing storm water, they cannot treat the pollutants leaking form vehicle on roads.
How does it work?
Porous pavement includes pervious surface, bedding layer, reservoir layer and filter layer3: the surface layer directly receives the traffic load and
Bibliography: Ferguson, Bruce K. 2005. Porous Pavements. Integrative Studies in Water Management and Land Development. Boca Raton: CRC Press/Taylor and Francis. http://www.loc.gov/catdir/toc/ecip0421/2004019318.html Minnesota Stormwater Manual. http://stormwater.pca.state.mn.us/ EPA: United States Environmental Protection Agency http://www.epa.gov/ DCR, 1999, Et seq. Virginia Storm water Management Handbook. http://www.virginiadot.org/business/resources/LocDes/BMP_Design-Manual/Chapter_10_Porous_Pavement.pdf City of Colorado Springs. Section 2. Pavement Design Criteria Manual http://www.springsgov.com/Files/Pavement%20Design%20Criteria%20Manual.pdf