SIST-TS CEN/TS 18041:2024
(Main)Hydrometry - Sedimentation - Measurements required for effective sediment management and control at river structures
Hydrometry - Sedimentation - Measurements required for effective sediment management and control at river structures
This document provides guidance on the collation of the measurements required for the management of siltation at river structures. These include structures used by water supply utilities, other major water abstractors, HEP producers, and for flow measurement by environmental protection agencies.
The document is also intended for use when a redundant structure is being removed, or when modifications to a structure are being made to facilitate fish migration or for river restoration. This is to ensure that the impacts of these changes are adequately monitored and recorded.
The document covers the provision of routine measurements, and the checks and requirements that need to be made by the operator so that specific basic information is collated and made readily available. This information is used to inform decision-making by environment management agencies that authorise flushing, sediment clearance or sedimentation removal. This is to ensure minimal environmental impacts, and to compliance with existing environmental legislation.
Hydrometrie - Sedimentation - Erforderliche Messungen für effektives Sedimentmanagement und effektive Sedimentkontrollen an Flussstrukturen
Hidrometrija - Sedimentacija - Meritve, potrebne za učinkovito upravljanje in nadzor sedimentov na rečnih strukturah
Ta dokument podaja smernice za razvrščanje meritev, potrebnih za upravljanje zamuljevanja rečnih struktur. To vključuje strukture, ki jih uporabljajo vodovodna podjetja, drugi večji črpalci vode, proizvajalci električne energije iz vodnih virov in agencije za varstvo okolja za merjenje pretoka.
Dokument se uporablja tudi pri odstranjevanju odvečne strukture ali njenem spreminjanju za enostavnejšo migracijo rib ali za obnovo reke. S tem se zagotovita ustrezno spremljanje in beleženje vplivov teh sprememb.
Dokument zajema izvajanje rutinskih meritev ter preverjanja in zahteve, ki jih mora izpolnjevati upravljavec, da se omogoči zbiranje nekaterih osnovnih informacij in njihova dostopnost. Na podlagi teh informacij agencije za okolje sprejemajo odločitve v zvezi z izpiranjem, čiščenjem sedimentov in odstranjevanjem sedimentacije. To zagotavlja minimalne vplive na okolje in skladnost z obstoječo okoljsko zakonodajo.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2024
Hidrometrija - Sedimentacija - Meritve, potrebne za učinkovito upravljanje in
nadzor sedimentov na rečnih strukturah
Hydrometry - Sedimentation - Measurements required for effective sediment
management and control at river structures
Hydrometrie - Sedimentation - Erforderliche Messungen für effektives
Sedimentmanagement und effektive Sedimentkontrollen an Flussstrukturen
Ta slovenski standard je istoveten z: CEN/TS 18041:2024
ICS:
17.120.20 Pretok v odprtih kanalih Flow in open channels
93.140 Gradnja vodnih poti, Construction of waterways,
pristanišč in nasipov ports and dykes
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
CEN/TS 18041
TECHNICAL SPECIFICATION
SPÉCIFICATION TECHNIQUE
May 2024
TECHNISCHE SPEZIFIKATION
ICS 17.120.20; 93.140
English Version
Hydrometry - Sedimentation - Measurements required for
effective sediment management and control at river
structures
Hydrometrie - Sedimentation - Erforderliche
Messungen für effektives Sedimentmanagement und
effektive Sedimentkontrollen an Flussstrukturen
This Technical Specification (CEN/TS) was approved by CEN on 1 April 2024 for provisional application.
The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to
submit their comments, particularly on the question whether the CEN/TS can be converted into a European Standard.
CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS
available promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in
parallel to the CEN/TS) until the final decision about the possible conversion of the CEN/TS into an EN is reached.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 18041:2024 E
worldwide for CEN national Members.
Contents Page
European foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 Underpinning legislation and regulations . 5
5 Collection of data and information . 6
5.1 General. 6
5.2 Existing data and information . 6
5.3 Hydrometric data and other data requirements . 7
5.3.1 General. 7
5.3.2 Daily rainfall patterns across the catchment . 7
5.3.3 Channel cross-section and velocity profiles . 7
5.3.4 River level . 8
5.3.5 River discharge and water velocity . 8
5.3.6 Water quality . 8
5.3.7 Biodiversity . 8
5.4 Sediment characteristics . 8
5.5 Additional information for other structures on the watercourse . 8
6 Establishing the monitoring programme and related activities . 9
6.1 General. 9
6.2 Costing . 9
6.3 Frequency of the measurements . 9
6.4 Duration of the monitoring programme . 9
6.5 Monitoring techniques and methods to be used . 9
7 Impact on carbon emissions . 9
8 Allowing for uncertainty . 10
Annex A (informative) A case study - Weir removal considerations on the River Rother,
West Sussex, UK . 11
Annex B (informative) A decision tree for transverse weir removal, based on ecological
benefits and cost . 13
Bibliography . 15
European foreword
This document (CEN/TS 18041:2024) has been prepared by Technical Committee CEN/TC 318
“Hydrometry”, the secretariat of which is held by BSI.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN/CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Introduction
The need for this document stems from the lack of concise guidance that is available on sediment
management in watercourses. Previously, bespoke procedures for undertaking sediment management
activities at discrete locations have been developed to address a specific local problem. These
procedures usually required a data gathering exercise that delayed the implementation of the
management plan. These procedures and the data that supported them, only addressed the issues at the
individual local sites. There is, however, no generic or standardized approach to the routine collection
of data and information that can be undertaken in advance of an application to manage sedimentation.
This document will therefore help the user to build up a database of required measurements and other
related information to support the sediment management plan.
It is envisaged that the users of this document will include government agencies that have legislative
powers to manage the natural environment, individuals or organisations that wish to develop a river
site by the construction of structure that will interfere with the natural sediment process in the water
course, or owners of existing structures that wish to manage the sedimentation at the structure or
remove the structure from the channel.
To assist the user in understanding the full range of issues that may require addressing, an example of
the requirements of a sediment management plan is given in Annex A. This gives details of what issues
had to be considered when a weir removal plan was developed for the River Rother in West Sussex in
the UK.
To assist the user in devising the detail of a sediment management plan, Annex B is included, and shows
a decision tree that will help put into context the detailed decisions required in deploying a
management plan across a complex catchment with a number of sites where weirs could be removed.
1 Scope
This document provides guidance on the collation of the measurements required for the management of
sedimentation at river structures. These include structures used by water supply utilities, other major
water abstractors, HEP producers, bridges, and for flow measurement by environmental protection
agencies. It is intended to be used at sites where the sediment ranges in particle size from fine colloidal
material to coarse gravel, that is, sediment normally transported by flood flows. It is not intended for
use at sites where major channel bed regrading is to be undertaken requiring the major excavation of
solid bed material.
The document is also intended for use when a redundant structure is being removed, or when
modifications to a structure are being made to facilitate fish migration or for river restoration. This is to
ensure that the impacts of these changes are adequately monitored and recorded.
The document covers the provision of routine measurements, and the checks and requirements that are
to be made by the operator so that specific basic information is collated and made readily available. This
information is used to inform decision-making by environment management agencies that authorize
flushing, sediment clearance or sedimentation removal. This is to ensure minimal environmental
impacts, and to support compliance with existing environmental legislation.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
4 Underpinning legislation and regulations
When considering the requirements of sediment management, it is essential to understand what
relevant legislation and regulations are currently in force that impact on this activity. This will
determine the type of measurements that are taken and the duration of the monitoring programme.
Examples of such legislation and regulations include Environmental Bills and Acts of Parliament,
current Drought Orders, current Drought Permits, local by-laws, Strategic Environmental Assessments
relating to the watercourse and its catchment, and details of any environmentally sensitive sites within
the catchment of the watercourse, e.g. sites of specific scientific interest (SSSIs in the UK and sites
designated SAC, SPA and RAMSAR Worldwide. Some structures are subject to preservation orders and
planning restrictions, e.g. listed buildings in the UK.
5 Collection of data and information
5.1 General
The measurements required for the management of sedimentation at a river structure should be
determined by analysing data on:
— relevant legislation and regulations currently in force that impact the management of
sedimentation (Clause 4);
— hydrometric data (5.3) including:
— daily rainfall patterns across the catchment (5.3.2);
— channel cross-section and velocity profiles (5.3.3);
— river level (5.3.4);
— river discharge and water velocity (5.3.5);
— water quality (5.3.6);
— biodiversity (5.3.7);
— sediment characteristics (5.4);
— information on other structures on the watercourse (5.5.);
This data will influence the type of measurements that are taken and the duration of the monitoring
programme at the area of interest. Additionally, it is important to include any measurements required
at locations well downstream of the area of interest that will be affected by the proposed work. This will
impact on the costing of the proposed plan (6.2).
5.2 Existing data and information
The flow characteristics of the watercourse at the structure, and other impacted sites within the
catchment, should be defined. This, together with more general catchment-wide descriptors will help
the understanding of the nature of sediment movement within the catchment. To this end, a listing of all
existing flow statistics for the catchment should be provided and reviewed to help determine what
additional data are needed. This should include:
— any water velocity data if available, as this defines the power of the watercourse to create and
distribute sediment;
— where it is considered important for the long-term sustainable management of sediment it may be
appropriate to collect data relating to the supply of sediment, e.g. areas of unstable surface
deposits, active channel erosion;
— key characteristics of the hydrological regime, e.g. density of drainage network, response to rainfall
and flow range;
— stream power within the contributing reach and catchment physiographic characteristics such as
geology and land use that may control sediment supply.
It should be stated whether the existing data are based on actual measurements or derived from
surrogate measured catchments or catchment modelling. If simulated or modelled data are used, the
details of the methodology used in their derivation should be provided to help the better understanding
of the potential errors and uncertainties in the data.
5.3 Hydrometric data and other data requirements
5.3.1 General
If a significant period of existing data exists, i.e. greater than ten years, the data may be used to estimate
the frequency of a particular range of flows that impact on sediment movement [1]. In this case, the
continuation of the monitoring programme should reflect this and seek to increase the accuracy and
statistical significance of the frequency analysis.
If the existing data do not provide adequate details to formulate the sediment management plan,
additional hydrometric and other data will be required. The choice of data to be collected should reflect
the use to which they will be put.
For example, if hydrological and hydraulic modelling is to be undertaken using the data, then the spatial
and temporal distribution of the data has to be appropriate to the type of modelling to be undertaken.
5.3.2 Daily rainfall patterns across the catchment
Daily rainfall patterns across the catchment should include details of any rainfall intensity records from
significant rainfall and flood events. This will help determine the frequency and nature of storms and
flood events that impact on the sediment regime in the catchment. If long term rainfall records are
available, it is beneficial to establish if rainfall data exhibit stationarity or show changes in magnitude
and frequency reflecting climate change. This can give an indication of whether rates of sedimentation
are changing within the catchment.
5.3.3 Channel cross-section and velocity profiles
Channel cross-surveys, including bathymetric surveys, and velocity profiles should be taken at the point
of interest. These should extend both upstream and downstream for an appropriate distance. Advice on
the required extent of the survey upstream and downstream can be sought from the environmental
regulation authority and review of specific publications [2].
The velocity profiles should be established using multi-point flow measurement techniques, done in
such a way as to clearly show areas of rapid erosive flow, and areas of more steady flow where
deposition could be occurring. The channel cross-sections should show the accumulation of sediment as
distinct from the solid geology over which the watercourse flows. Discretion is needed when deciding
how far upstream and downstream the surveys should extend, and advice can be sought from the
appropriate regulatory body.
Whilst these measurements can be used to derive a stage-discharge relationship at the point of
measurement, the production of a channel rating is not the primary objective of the monitoring
programme.
An alternative approach is to build a 1D hydraulic model of the study reach, collect bed sediment
particle size distribution data (PSD data) and then combine the Shear Stress or Stream Power outputs
from the 1D model with the PSD data to estimate under what flow states size fractions may be
mobilised, and also estimate sediment transport rates. This alternative approach will involve modelling
expertise and may therefore prove unjustifiable in terms of costs.
5.3.4 River level
River level data at the site can be used to define how sediment transport is affected by the transition
from in-bank to out-of-bank flows. At sites where weir removal is the intention, detailed water level
measurements should be taken both upstream and downstream of the weir so that projections of the
change in water level after weir removal can be made. The extent of the measurement upstream and
downstream will depend on the size of the structure to be removed, and it may be necessary to
undertake simple backwater calculations to indicate the likely change in water level [3].
5.3.5 River discharge and water velocity
River discharge and water velocity data can be used to estimate the capacity of the river to entrain the
sediment and convey it away from the site.
5.3.6 Water quality
Water quality data should be obtained in order to define an
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