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7/30/2019 Hydrographic Survey & Its Purposes By D.M Siddique
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Date: 08/11/2012
Hydrographic SurveyingLecture 17 : Hydrographic survey and its
purposes
Dr. Mohsin Siddique
NU-FAST Lahore Campus
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Hydrographic Survey
Hydrograph survey include all types of hydrological observations
which are necessary for the design of hydraulic, or marine
structures.
Hydrograph survey is the branch of surveying which deals with
any body of still or running water such as a lake, harbor, stream or
.
water features.
Hydrographic survey is the science of measurement and
description of features which affect maritime navigation, marineconstruction, dredging, offshore oil exploration/drilling and related
activities.
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Hydrographic Survey
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Gold Coast Lake Saif ul Maluk
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Hydrographic Survey
Tarbela dam
Indus river
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Hydrographic Survey
The illustration highlights the importance of
accurate and reliable hydrographic survey
information for safe and efficient navigation.
Bathymetry surveying by Echo sounding.
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Note: Depth of the seabed
below the survey vessel is
known as sounding
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Hydrographic Survey
Hydrographic sur vey includes the following
1. Rain gauging
2. River gauging
3. Marine survey
1. Rain au in :
The amount of rainfall in the catchment area of a basin or a river isgenerally recorded. This helps to predict the probably run-off
through the basin or river
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Hydrographic Survey
2. River gauging:
River gauging involves the measurement of discharge of a river and
the establishment of a gauge post on one of its banks.
This is done to directly read the Highest Flood Level (HFL) so that
the warning may be given to surrounding areas.
Measurement of river discharge require surveys for river cross-
sectional area and flow velocity
3. Marine survey:
It involves marking of shore line at high and low tides, determining
depth of water around the harbor by echo-sounder, current and tideobservations, and preparing of maps etc.
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Purposes of Hydrographic Survey
(1). Measurements of tides for sea coastal work , such as
construction of sea defense works, jetties and harbors, for the
establishment of a leveling datum, and for reducing sounding
(2) Determination of bed depths, by sounding
(a). For navigation, i.e., for tow out routes for production
p at orms ut a so inc u ing t e ocations o roc s, san ars,navigation lights and buoys
(b). For location of underwater works, volumes of underwater
excavation etc,;
(c). In connection with irrigation and land drainage schemes
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Purposes of Hydrographic Survey
(3) Determination of direction of currents in connection
with
(a). location of sewer outfall
(b). determination of areas subjected to scour and siltation
(c). for navigational purposes.
(4) Measurement of quality of water and flow of water inconnection with water schemes, power schemes and flood
control.
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Methods of Hydrographic Surveying
Horizontal control: It may consists of triangulation along the
coast or shoreline. To provide additional control theodolite
traverses are run in between triangulation stations.
The triangulation work is known as primary horizontal control andtheodolite traversing in known as secondary horizontal control.
Vertical control: A number of precision bench marks are
established along the shore line. They are used for checking and
setting tide gauges in which sounding are referred to find the depth
of water. Hence vertical control must be established to connect thegauges with shore elevations and also with each other.
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Thank you
Questions….
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