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Assessment of soil flooding in cities by electrophysical methods

Publication Type:

Journal Article

Source:

Eurasian Soil Science, Volume 41, Issue 10, p.1059 - 1065 (2008)

ISBN:

1064-2293

URL:

http://www.landviser.net/webfm_send/7

Ключевые слова (Keywords):

electrical potential, electrical resistivity, ER, LandMapper, self-potential, SP

Abstract:

The degree and localization of soil flooding have been assessed in the cities of Rostov Velikii and Astrakhan by the vertical electric sounding method. It has been proved that this method permits one to reliably reveal strongly excessively moistened (flooded) soils and to discover the groundwater level using measurements from the surface without digging profiles and boring drill holes.

Notes:

(1) The method of vertical electric sounding is
applicable for obtaining the generalized characteristics
of flooding under urban conditions without drilling
boreholes and digging pits and involves only making
measurements directly from the soil surface.
(2) In arid regions (Astrakhan), these studies are
more unambiguous, since the curve of the moisture and
resistivity distribution is mainly controlled by the
groundwater level. The groundwater salinity also
sharply lowers the resistivity and thus forms a clearly
differentiated two-layered VES curve. The upper part
of the soil is dried and has a low resistivity.
(3) The electrophysical soil investigations in the
town of Rostov Velikii proved that the flooding pattern
is complicated and diverse there. For a more comprehensive
assessment of the flooding in this town, a more
detailed survey probably including up to a hundred
sounding points with control drilling of holes is
required. Nevertheless, we may state that, in addition to
Lake Nero, there are a lot of different sources of excessive
soil moistening and flooding. The main flooding
zones were revealed using only vertical electric sounding.
a Nero Lake

For the resistivity measurements using the VES method and the identification of flooding and excessive moistening under the urban conditions, we used a LandMapper-03 device developed by Astro-group Co.
(Russia) for the Landviser Co. (USA). This instrument measures the electric parameters of soils (in particular,
the electric resistivity) using the VES method. The graphs of these relationships are called VES curves or
functions of the relationship between the apparent resistivity and the electrode semispacing AB/2. These
curves contain information about the resistivity variation with the depth, though not directly but via the electrode spacing on the soil surface. It is clear that the depth of the resistivity measurement depends in an
involved manner on the resistivity proper [6, 7].

Rostov Velikii is situated within the Rostov Lowland.
Therefore, the problem of city flooding is related
to its location, which is close to Lake Nero. In addition,
according to some evidence, the flooding in this vast
area is caused to a certain extent by the specific multiple-
factor conditions of water management within the
epicenter of Lake Nero.

The soil cover in a modern city is a very complicated
soil body. It is formed of anthropogenic bodies rather
than of natural soils. The former represents mixed
extraneous (with respect to soils) material of various
origins: industrial waste and garbage, nutrient mixtures
with intense pedoturbations, and massifs pierced with
communication openings and lines. This is particularly
true for the central historical part of cities. In the historical
parts of a city, where preservation of cultural and
historical monuments is of great importance, the soil
cover is still more complex. In addition, a lot of problems
are induced by modern urban life and its influence
on the monuments. These are various kinds of impacts
and, above all, flooding.