Urbanization and the Geoenvironment - Sustainable Practices in Geoenvironmental Engineering - page 221

TABLE 7.1
Soil Physical Properties for Various Urban Uses

Requirement Soil Properties Application

Drainage Hydrology, hydraulic conductivity (soil

structure), porosity

Playing ields, efluent disposal

Load-bearing
capacity

Bulk density, compactability, water content/
potential, penetration resistance, shear
strength, compressibility, consolidation

Playing ields, foot paths, load bearing
support for surface infrastructures,
and spread footings for light structures

Plant growth
medium

Drainage, air capacity, water capacity, bulk
density, structure, penetration resistance

Playing ields, gardens, parks or sports
ields

Prevention of
erosion and runoff

Iniltration, drainage, structural stability Foot paths, efluent disposal, parks, or

sports ields

Source: Adapted from Mullins, C.E., Physical properties of soils in urban areas. In P. Bullick and P.J. Gregory
(eds.), Soils in the Urban Environment , Blackwell Scientiic Publications, Oxford, pp. 87-118, 1990.

to return the land to its intended land use (Mullins, 1990). Signs of deterioration could
include ponding, runoff, soil erosion, or poor grass growth. Soil properties relevant for
use, soil type, and sensitivity of the properties to changes in soil use are important factors
in mitigating soil damage. Some of the properties required for various uses are summa-
rized in Table 7.1.
Derelict sites pose some unique problems. In general, these sites have become by default
disposal sites with unauthorized disposed goods and substances that include urban gar-
den wastes and other kinds of household wastes. Perhaps, the more dominant kinds of
debris found in derelict sites are those items that are the result of demolished buildings or
buildings in considerable distress. The debris generally found includes building materials
such as pipes, pieces of foundations, tiles, wood, plaster, rusting steel, and broken concrete
slabs and structures.

7.3 Impact of Urbanization on WEHAB
7.3.1 Impact on Water

In urban and suburban areas, more and more land surfaces are covered by buildings,
roads, and constructed parking areas using concrete, bituminous concrete, asphalt, or
other impervious coverings. Because these covered surfaces prevent iniltration of rainwa-
ter and ponded water into the subsurface, replenishment of the underlying groundwater
is denied, and groundwater levels may consequently be lowered. Another effect of such
covered surfaces is to allow surface low (i.e., streaming) of rainwater into collecting areas.
It is not uncommon to ind contaminants in the surface low water or streaming water
because of noxious substances deposited onto the covered surfaces. Since these waters will
eventually ind their way into the receiving waters, they can be considered to be a non-
point source contamination of lakes and rivers.
An extensive underground system of parking areas, sewers, pipes, deep building foun-
dations, and tunnels to depths of 100 m can also signiicantly affect the underground
terrain. Water leakage from buried and degrading water supply pipes leads to excessive