ISO 11329:1998
(Main)Hydrometric determinations — Measurement of suspended sediment transport in tidal channels
Hydrometric determinations — Measurement of suspended sediment transport in tidal channels
Déterminations hydrométriques — Mesurage du transport solide dans les canaux à marée
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 11329
First edition
1998-12-15
Hydrometric determinations —
Measurement of suspended sediment
transport in tidal channels
Déterminations hydrométriques — Mesurage du transport solide dans les
canaux à marée
A
Reference number
ISO 11329:1998(E)
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ISO 11329:1998(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
International Standard ISO 11329 was prepared by Technical Committee ISO/TC 113, Hydrometric determinations,
Subcommittee SC 6, Sediment transport.
© ISO 1998
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means, electronic
or mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
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Printed in Switzerland
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© ISO
ISO 11329:1998(E)
Introduction
Estuaries and creeks have become regions of major developments pertaining to port and harbour facilities,
navigation, reclamation and effluent disposal. Human interference with water bodies, for example, providing
navigational channels, installing major or minor structures and reclaiming land, need thorough examination of their
impact on morphological changes, stability of banks and channels, the consequences of capital and maintenance
dredging, and the selection of disposal grounds. For these purposes, it is necessary to estimate the suspended
sediment transport rates in tidal channels, which can be based on data on morphological characteristics of the
channel, flowrates and the corresponding suspended sediment concentration.
In comparison to the situation in unidirectional flow, the flow as well as sediment concentration at different locations
along tidal channels are much more complex. The salt water flow from the sea at one end and the fresh water flow
from the river at the other end are responsible for spatial and temporal variations in water and sediment movement
in tidal channels. When measuring the flowrate and suspended sediment concentrations for estimating sediment
transport rates, these factors need to be considered.
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INTERNATIONAL STANDARD © ISO ISO 11329:1998(E)
Hydrometric determinations — Measurement of suspended
sediment transport in tidal channels
1 Scope
This International Standard deals with the method and techniques for the sampling of suspended sediment and
estimation of sediment transport rates in natural and man-made channels influences by tidal action.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative documents referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 772,
Hydrometric determinations — Vocabulary and symbols.
ISO 2425, Methods for hydrometric measurements under tidal conditions.
3 Terms and definitions
For the purposes of this International Standard, the terms and definitions given in ISO 772 and the following apply.
3.1
mixed tides
tides which have two markedly unequal successive high waters, or two markedly unequal successive low waters, or
both, during most of each month
3.2
divergence
deviation of the angle between the flood and ebb axes from 180°
NOTE In a straight reach, the flood and ebb flow directions are ideally expected to lie on the same axis but in the opposite
direction, i.e. the change in flow direction is 180°. However, in most situations the directions of flood and ebb flows are not
along the same axis, due to prevailing approach conditions from either side.
3.3
flood [ebb] predominance
net flow, either in the flood or in the ebb direction, resulting when the flood and ebb velocity-time curves are such
that the net flow integrated over a tidal period, either at a point or over a vertical, is not zero
NOTE In a typical situation, one part of a tidal channel may have flood predominance whereas the other may have ebb
predominance.
3.4
creek
inlet or arm of a river or a small stream joining the coast
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ISO 11329:1998(E)
4 Salient features of sediment transport in tidal channels
Measurement of discharge and estimation of corresponding suspended sediment concentration by analysis of water
samples are essential to estimating the rate of sediment transport through a channel section. The following aspects
shall be taken into account when planning the collection of data and estimation of sediment transport.
a) Flow is two-way in tidal channels as a result of tidal fluctuation in the sea. During the flood phase, the water
level rises and the flow is from the sea toward the upstream, whereas during the ebb phase, the water level
falls and the flow is seaward.
b) The extent of tidal excursion, magnitude and direction of tidal current, and flood and ebb periods (at any cross-
section) differ from tide to tide depending on the tidal range and freshwater discharge.
c) The variation in water level from section to section in a tidal channel depends on the freshwater discharge, tidal
range in the sea, the channel bed slope and frictional resistance at the bed and banks of the channel.
d) All the above aspects result in temporal and spatial variation in the sediment transport at all points in a tidal
channel.
e) The quantity and type of sediment which enters a tidal channel depends on the freshwater discharge, the wave
climate and tides in the sea. As a result, there can be a large variation in the amount of suspended load in tidal
channels.
f) The variation in the strength of the current from spring to neap or from neap to spring results in significant
changes in the bed configuration along the channel. Variation in the freshwater discharge also causes such
changes.
g) The directions of flood and ebb currents in a cross-section do not necessarily differ by 180°, (i.e. complete
reversal), as the flow is governed by the bed and bank configurations upstream of flow. Furthermore, the flood
flow may dominate one part of the cross-section whereas the ebb flow dominates the other part.
h) The time of reversal and the direction of transport are commonly different across the cross-section and at
different depths on a vertical.
i) In a wide channel near the mouth, the time of reversal from flood to ebb or from ebb to flood differs appreciably
from one part to another in the section, resulting in a large circulation.
j) The difference in densities of sea water and river water affects the mixing characteristics of tidal and freshwater
flows, depending on their relatives magnitudes. The flow in the channel can be well-mixed, partially mixed or
stratified.
k) Water level is affected by atmospheric pressure fluctuations and wind drag.
l) Biological effects can determine the erosivity within an estuary, which can affect the suspended sediment
concentrations in time and space.
m) Variations in temperature change water viscosity and also affect the settling velocity of different sediments,
thus affecting the suspended sediment load throughout the year.
n) Human activities, such as dredging, disposal and trawling, will also influence the amount of suspended
sediment within the water column.
5 Guidelines for measurement and estimation of suspended sediment transport
a) Long-term measurements of flow and simultaneous water sampling are required for estimating sediment
transport in tidal channels. For regular semidiurnal tides, data should be collected for a minimum of 13 h.
However, in case of diurnal tides or where there is a strong diurnal component (mixed tides), an observation
period of 25 h is recommended. The time interval between the observations shall also be kept as small as
possible (no more than 0,5 h) due to the unsteady nature of tidal flow.
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ISO 11329:1998(E)
b) The period of data collection may need to cover various ranges of tide, from neap to spring, to account for the
variation in velocity and suspended sediment concentration if morphological changes are to be estimated.
c) During the preliminary survey, the mixing characteristics of the tidal channel shall be identified by taking
simultaneous observations at surface and at bed. If flow is stratified, it may be necessary to extend the
observation period to cover a period from neap to spring tides.
d) As the presence of freshwater discharge affects the flow field and sediment transport, collection of data is
necessary to cover both dry and freshet seasons.
e) Items a) through d) emphasize the need for long-term observations. Depending on the hydraulic conditions, a
decision should be taken on the required period and time of observations to serve the purpose for which the
investigation is undertaken. It may also be possible to limit the field observations if suitable numerical models
are available to simulate the range of prevailing hydraulic condi
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