Water quality - Guidance on determining the degree of modification of the hydromorphological features of transitional and coastal waters

This European Standard provides guidance on characterizing the modifications of the hydromorphological features of TraC waters described in EN 16503, enabling consistent comparisons of hydromorphological modification between TraC waters within a country and between different countries in Europe. Its primary aim is to assess ‘departure from naturalness’ as a result of human pressures on TraC hydromorphology, and it suggests suitable sources of information that may contribute to describing the modification of hydromorphological features. The procedures set out in this standard will encourage the objective assessment and reporting of the variability in transitional and coastal waters, and contribute to the work needed to implement the WFD and the MSFD; however, it does not replace methods that have been developed for local assessment and reporting.

Wasserbeschaffenheit - Anleitung zur Bestimmung der Veränderung hydromorphologischer Merkmale von Übergangs- und Küstengewässern

Dieses Dokument enthält eine Anleitung zur Bestimmung der Ausprägung hydromorphologischer Merkmale von TraC Gewässern nach der Beschreibung in EN 16503 und ermöglicht konsistente Vergleiche hydro¬morphologischer Veränderungen zwischen TraC Gewässern innerhalb eines Staates und zwischen verschiedenen europäischen Staaten. Ihr vorrangiges Ziel ist die Klassifikation der „Abweichung von der Naturbelassenheit“ als Folge vom Menschen verursachter Belastungen der TraC Hydromorphologie, und sie empfiehlt geeignete Informationsquellen, die zur Darstellung der Veränderung hydromorphologischer Merkmale beitragen können. Die in dieser Norm aufgestellten Verfahren unterstützen die objektive Bewertung und Berichterstattung über die Veränderlichkeit in TraC Gewässern und leisten einen Beitrag zur Umsetzung der WRRL und der MSRL; es werden jedoch keine Verfahren ersetzt, die für lokale Klassifikation und Berichterstattung entwickelt wurden.

Qualité de l'eau - Guide pour la détermination du degré de modification des caractéristiques hydromorphologiques des eaux de transition et des eaux côtières

Le présent document fournit des orientations sur la caractérisation des modifications des caractéristiques hydromorphologiques des eaux de transition et des eaux côtières décrites dans l’EN 16503, permettant des comparaisons fiables de la modification hydromorphologique entre les eaux de transition et des eaux côtières au sein d’un même pays et entre différents pays d’Europe. Son principal objectif est d’évaluer l’écart par rapport au caractère naturel résultant des pressions anthropiques sur l’hydromorphologie des eaux de transition et des eaux côtières. Il suggère également des sources d’informations appropriées susceptibles de contribuer à la description de la modification des caractéristiques hydromorphologiques. Les modes opératoires décrits dans la présente norme favoriseront l’évaluation objective et le rapportage de la variabilité des eaux de transition et des eaux côtières, et contribueront au travail de mise en oeuvre des directives DCE et DCSMM ; cependant, ils ne remplacent pas les méthodes mises au point pour l’évaluation locale et le rapportage.

Kakovost vode - Navodilo za določevanje stopnje spremenjenosti hidromorfoloških značilnosti somornic in obalnih morij

Ta dokument podaja navodilo za določevanje stopnje spremenjenosti hidromorfoloških značilnosti somornic in obalnih morij.

General Information

Status
Published
Publication Date
11-Dec-2018
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
12-Dec-2018
Completion Date
12-Dec-2018

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SLOVENSKI STANDARD
SIST EN 17123:2019
01-maj-2019
.DNRYRVWYRGH1DYRGLOR]DGRORþHYDQMHVWRSQMHVSUHPHQMHQRVWL
KLGURPRUIRORãNLK]QDþLOQRVWLVRPRUQLFLQREDOQLKPRULM
Water quality - Guidance on determining the degree of modification of the
hydromorphological features of transitional and coastal waters
Wasserbeschaffenheit - Anleitung zur Bestimmung der Ausprägung
hydromorphologischer Merkmale der Übergangs- und Küstengewässer

Qualité de l'eau - Document d'orientation sur la détermination du degré d'altération des

caractéristiques hydromorphologiques des eaux de transition et des eaux côtières
Ta slovenski standard je istoveten z: EN 17123:2018
ICS:
07.060 Geologija. Meteorologija. Geology. Meteorology.
Hidrologija Hydrology
13.060.10 Voda iz naravnih virov Water of natural resources
SIST EN 17123:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 17123:2019
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SIST EN 17123:2019
EN 17123
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2018
EUROPÄISCHE NORM
ICS 07.060; 13.060.10
English Version
Water quality - Guidance on determining the degree of
modification of the hydromorphological features of
transitional and coastal waters

Qualité de l'eau - Guide pour la détermination du degré Wasserbeschaffenheit - Anleitung zur Bestimmung der

de modification des caractéristiques Ausprägung hydromorphologischer Merkmale der

hydromorphologiques des eaux de transition et des Übergangs- und Küstengewässer
eaux côtières
This European Standard was approved by CEN on 5 October 2018.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this

European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by

translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management

Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey 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

© 2018 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17123:2018 E

worldwide for CEN national Members.
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EN 17123:2018 (E)
Contents Page

European foreword ....................................................................................................................................................... 3

Introduction .................................................................................................................................................................... 4

1 Scope .................................................................................................................................................................... 5

2 Normative references .................................................................................................................................... 5

3 Terms and definitions ................................................................................................................................... 5

4 Principle .......................................................................................................................................................... 11

5 Determining the hydromorphological modifications of transitional and coastal

waters ............................................................................................................................................................... 11

5.1 Survey strategy ............................................................................................................................................. 11

5.2 Defining hydromorphological units ...................................................................................................... 13

5.3 Procedure for scoring ................................................................................................................................. 13

6 Interpreting and reporting hydromorphological modifications ................................................ 14

6.1 Minimum requirements for reporting ................................................................................................. 14

6.2 Assigning classification terms ................................................................................................................. 15

Annex A (normative) Protocol for scoring ......................................................................................................... 16

Annex B (normative) Formulae for use in quantitative scoring of selected features ........................ 37

Bibliography ................................................................................................................................................................. 39

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European foreword

This document (EN 17123:2018) has been prepared by Technical Committee CEN/TC 230 “Water

analysis”, the secretariat of which is held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by June 2019, and conflicting national standards shall be

withdrawn at the latest by June 2019.

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.

According to the CEN-CENELEC Internal Regulations, the national standards organisations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,

Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,

France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,

Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and the United Kingdom.
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Introduction

This document will enable broad assessments and comparisons to be made of the hydromorphological

modifications of Transitional (estuaries, lagoons, etc) and Coastal waters (TraC waters) throughout

Europe (e.g. for reporting by the European Environment Agency). These systems have been increasingly

influenced by human activities over many centuries and hence the modifications relate to historical and

recent developments that are superimposed over the natural and large-scale changes and variability

experienced by these systems.

This document attempts to acknowledge the particular spatial and temporal heterogeneity of coastal

and transitional systems. TraC systems are dominated by multi-directional processes (waves acting in

different directions, as well as bi-directional tidal flows operating at differing tidal levels, which can be

further complicated by variable wind orientation). As a result, the natural variability within coastal and

transitional water bodies can often be significant in spatial and temporal scales, which need to be

reflected during comparisons against natural baselines or reference conditions.

European Directives such as the Water Framework Directive (WFD)[ref 1] and the Marine Strategy

Framework Directive (MSFD) [ref 2] require Member States to determine that hydromorphological and

physico-chemical conditions should be suitable for supporting biological assemblages; the WFD and

MSFD in turn require Member States to indicate, respectively, that good ecological status and good

environmental status have been attained. The MSFD descriptors, criteria and indicators include

hydromorphological features.

EN 16503 (Water quality — Guidance standard on assessing the hydromorphological features of

transitional and coastal waters) describes a protocol for field survey and feature recording, whereas this

standard gives guidance on assessing the modification of TraC hydromorphological features. It focuses

especially on human pressures that affect TraC waters and thus will be valuable for implementing the

WFD by indicating the extent to which these pressures will cause a departure from hydromorphological

reference conditions.

Although the procedure described in this document enables the hydromorphological modification of

TraC waters to be determined and described, it does not attempt either to describe methods for

defining high status for hydromorphology under the WFD or to link broadscale hydromorphological

classification to assessments of ecological status. In addition to its relevance to the WFD and MSFD, this

standard has applications also for nature conservation, environmental impact assessment, river basin

management, flood and erosion risk assessment (e.g. the EC Floods Directive) [ref 3] and setting targets

for restoration. In addition, for the Habitats Directive [ref 4] there is a need to maintain certain

“features” in favourable condition, which has also given rise to a focus on hydromorphological

assessments.

(Note that in this standard, “assessment” is used as a broad term referring to the general description of

features and the pressures affecting them. It is not used to imply the judgement of particular levels of

“quality” or “value”, whether related to status under the WFD, MSFD or more generally.)

WARNING — Safety issues are paramount when surveying transitional and coastal waters. This

European Standard does not purport to address all of the safety problems, if any, associated with

its use. It is the responsibility of the user to establish appropriate health and safety practices

and to ensure compliance with any EU and national regulatory conditions or guidelines.

IMPORTANT — Persons using this document should be familiar with usual laboratory and

fieldwork practice. It is absolutely essential that tests conducted according to this document be

carried out by suitably trained staff.
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1 Scope

This document provides guidance on characterizing the modifications of the hydromorphological

features of TraC waters described in EN 16503, enabling consistent comparisons of

hydromorphological modification between TraC waters within a country and between different

countries in Europe. Its primary aim is to assess "departure from naturalness" as a result of human

pressures on TraC hydromorphology, and it suggests suitable sources of information that may

contribute to describing the modification of hydromorphological features. The procedures set out in

this standard will encourage the objective assessment and reporting of the variability in transitional

and coastal waters, and contribute to the work needed to implement the WFD and the MSFD; however,

it does not replace methods that have been developed for local assessment and reporting.

2 Normative references
There are no normative references in this document.
3 Terms and definitions

For the purposes of this document, the terms and definitions given and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at http://www.electropedia.org/
— ISO Online browsing platform: available at http://www.iso.org/obp
3.1
attribute
specific recorded element of a hydromorphological feature

EXAMPLE “Silt” and “boulders” are natural substrate attributes, “sheet piling” and “gabions” are attributes of

engineered banks.
[SOURCE: EN 16039:2011, definition 3.2]
3.2
bathymetry
shape of the sea-bed as measured by the distribution of depth
3.3
beach nourishment

artificial process of replenishing the beach using marine sediment (e.g. sand) to increase the

recreational value or to protect the beach against erosion
3.4
bedform pattern
morphology of the sea bed

Note 1 to entry: Refers to the morphology of soft bottoms. The bedform patterns may be simple or complex

depending on the size and shape of the system and the nature of the local sediment transport processes.

Deposition produces features such as sand and gravel bars, while erosion results in scour features.

[SOURCE: EN 16503:2014, definition 2.4]
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3.5
biogenic reef

mass consisting of the hard parts of organisms, or of a biogenically constructed frame enclosing detrital

particles, in a body of water
Note 1 to entry: Most biogenic reefs are made of corals or associated organisms.
[SOURCE: EN 16503:2014, definition 2.5]
3.6
biogenic structure

structure formed by organisms that when grouped together create physical habitats (e.g. reefs) or

stabilize sediments (e.g. seagrass beds, mussel beds)
3.7
breakwater
artificial structure used in coast protection to reduce wave energy
3.8
coastal cell

length of coastline confined by natural or artificial barriers across which little or no sediment is

transported
3.9
coastal water

surface water on the landward side of a line, every point of which is at a distance of one nautical mile on

the seaward side from the nearest point of the baseline from which the breadth of territorial waters is

measured, extending where appropriate up to the outer limit of transitional waters

Note 1 to entry: This definition from Article 2 of the EC Water Framework Directive (2000/60/EC) is one

example of a definition of “coastal water” used for legal purposes.
3.10
connectivity

linkage within and between water bodies and between water and land through exchange of water,

sediment and organisms
[SOURCE: EN 16503:2014, definition 2.9, modified]
3.11
delta

landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and

enters the sea
3.12
ecological status

expression of the quality of the structure and functioning of aquatic ecosystems, by comparing the

prevailing conditions with reference conditions

Note 1 to entry: As classified in accordance with Annex V of the EC Water Framework Directive (2000/60/EC).

[SOURCE: EN 16039:2011, definition 3.15]
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3.13
effective fetch

direct fetch, or distance in kilometres along which the wind blows from each direction, corrected by

fetches in directions of less than 45°
3.14
fetch
fetch length

distance of open water over which the wind can blow and generate wind-driven waves

[SOURCE: EN 16039:2011, definition 3.19, modified — “fetch length” was added as synonym]

3.15
fjord

long, narrow and glacially eroded inlet with steep sides, created in a valley often with a shallow

entrance at the mouth
[SOURCE: EN 16503:2014, definition 2.12]
3.16
groyne

coast protection structure built broadly perpendicular to the shoreline designed to reduce beach

erosion and trap sediment
3.17
highest astronomical tide
HAT

highest tide that can be expected to occur under average meteorological conditions and at the spring

and autumn equinox
[SOURCE: EN 16503:2014, definition 2.14]
3.18
hydromorphology

physical, hydrological and hydrodynamic characteristics of transitional and coastal waters including the

underlying processes from which they result
[SOURCE: EN 16039:2011, definition 3.22, modified]
3.19
intertidal area
foreshore
zone between high and low tide lines
[SOURCE: EN 16503:2014, definition 2.16]
3.20
lagoon

expanse of shallow coastal salt water, of varying salinity and water volume, wholly or partially

separated from the sea by sand banks or shingle, or, less frequently, by rocks
[SOURCE: EN 16503:2014, definition 2.17]
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3.21
land claim

conversion of submerged areas to increase the dry land available for agriculture or development

3.22
mixing

blending of waters of different characteristics (e.g. temperature, turbidity, salinity) by turbulence and

diffusion, caused by tides, winds, waves, currents and river runoff
[SOURCE: EN 16503:2014, definition 2.19]
3.23
normal tidal limit
NTL

point at which the level of a river or stream ceases to be affected by the tidal flow

[SOURCE: EN 16503:2014, definition 2.20]
3.24
openness
SEA
potential influence of the sea on the general hydrology of a lagoon
3.25
physiography
prominent coastal landform features
[SOURCE: EN 16503:2014, definition 2.21]
3.26
planform
view of transitional or coastal water body from above
EXAMPLE E.g. sinuous, straight.
[SOURCE: EN 16503:2014, definition 2.22]
3.27
reef
ridge of rock, or other material, lying seawards of the low water line
[SOURCE: EN 16503:2014, definition 2.23]
3.28
reference condition
condition which is totally or nearly totally undisturbed by human activity
[SOURCE: EN 16503:2014, definition 2.24]
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3.29
residence time
retention time
flushing rate

length of time it takes for a transitional water, sea loch, lagoon or fjord to exchange its water

Note 1 to entry: For enclosed bays “retention time” is the preferred term.
[SOURCE: EN 16503:2014, definition 2.25, modified]
3.30
ria
coastal inlet formed by partial submergence of a river valley
3.31
saltmarsh

area having characteristic vegetation adapted to saline soils and to periodic inundation by sea water

[SOURCE: EN 16503:2014, definition 2.26]
3.32
sandbank
low-energy feature created at the mouth of a river where it flows into the sea

Note 1 to entry: Sandbanks can also occur offshore, without the influence of rivers.

[SOURCE: EN 16503:2014, definition 2.27]
3.33
shore development
PSH
complexity of the perimeter of a lagoon
3.34
storm surge

change in water level as a result of meteorological forcing (wind, high or low barometric pressure)

additional to the astronomic tide; it may be positive or negative
[SOURCE: EN 16503:2014, definition 2.28]
3.35
stratification

layering of water column due to density differences resulting from changes in temperature, turbidity or

salinity with depth
[SOURCE: EN 16503:2014, definition 2.29]
3.36
substrate

rocky or sedimentary material making up the bed of a transitional or coastal water body

[SOURCE: EN 16503:2014, definition 2.30]
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3.37
subtidal area
zone seawards below the low tide line
[SOURCE: EN 16503:2014, definition 2.31]
3.38
tidal prism
volume of water that flows into a tidal channel on the flood tide
[SOURCE: EN ISO 772:2011, definition 2.49]
3.39
tidal range
difference in level between high water and low water of a tide
[SOURCE: EN ISO 772:2011, definition 2.50]
3.40
tidal regime

parameters characterising tides including levels, periods, frequencies, harmonics, phases and spectra

[SOURCE: EN 16503:2014, definition 2.34]
3.41
transitional water

body of surface water in the vicinity of river mouths which is partly saline in character as a result of its

proximity to coastal waters but which is substantially influenced by freshwater flows

Note 1 to entry: In accordance with Article 2 of the EC Water Framework Directive (2000/60/EC).

3.42
turbidity

reduction of transparency of a liquid caused by the presence of suspended particulate matter

[SOURCE: ISO 6107-2:2006, 145, modified]
3.43
wave exposure
wave energy environment of a shoreline

Note 1 to entry: An important variable, together with substrate composition and water depth, that influences

the habitat characteristics of the shoreline.
[SOURCE: EN 16503:2014, definition 2.39]
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4 Principle

A standard protocol is described for assessing the extent to which the hydromorphological features of

TraC waters are modified by human activities; transitional waters include estuaries, lagoons, deltas, rias

and fjords. These features have been divided into two groups — those that describe the static,

structural features, i.e. shape, underlying geology, sediment patterns, etc., and the dynamic, functional

processes, including water movements, sediment budgets and water characteristics. All of these are

given as generic types but can be adjusted in a site-specific context and are used to determine any

“departure from naturalness” as a result of human pressures on the hydromorphology of TraC waters.

Those structural and functional attributes then provide the fundamental niches that are colonized by

organisms and thus produce the biological assemblages characteristic of these areas.

The structural features often can be determined from easily available maps, charts, aerial photographs,

databases, or by remote sensing. The functional processes, on the other hand, need to be determined

within each water body and, given the high spatial and temporal variability in these features, usually

require an intensive sampling campaign or modelling procedure and also detailed and specialized

analysis and interpretation.

Given the difficulty in determining some functional attributes, both this European Standard and

EN 16503 gives more attention to TraC structural features which can be regarded as surrogates for

hydrodynamic processes. For example, the bed sediment grain size may reflect the hydrodynamic

regime.

The main output from this standard is a method for the assessment of the modification of

hydromorphological features of an entire estuary or other transitional water (TW), a part of it, or a

length of a coast. This includes parts of the TraC water bodies requiring restoration because of recent or

historical modification, or where near-natural conditions need to be protected.
5 Determining the hydromorphological modifications of transitional and
coastal waters
5.1 Survey strategy

The scale of survey is important in hydromorphological assessment of TraC waters, especially with

respect to resolution and connectivity, and in assessing the severity of impacts. Different survey

techniques are scale-dependent. Different applications require different levels of detail. In some

instances, survey may be extended beyond the hydromorphological units of interest to provide a

complete picture of the relevant physical processes involved. (For further details on survey strategy,

see EN 16503:2014, 4.2.)

Timing and frequency of survey will vary among the different TraC waters because of their individual

dynamic behaviour, and will depend upon the reason for assessment. Hydrodynamic attributes should

generally be recorded at a higher frequency than morphological attributes. The timing of survey will

depend upon the objectives of the work and the methods used. To measure certain conditions and

regimes in continuously changing dynamic systems, measurements should be continuous or periodic

according to the dominant daily, tidal, seasonal, lunar, annual or other cycles. The frequency of survey

should ideally be linked with the rate of hydromorphological change; this in turn is partly related to the

resistance to change and the resilience of the system to recover from a specific set of pressures. Other

survey frequencies may be dictated by specific monitoring requirements.

When comparing how a hydromorphological unit has changed, it is essential that these comparisons are

made under equivalent conditions, both spatially and temporally.

To ensure consistency in approach, the main feature categories are the same as those in EN 16503.

However, some minor adjustments have been made to the details to help facilitate scoring (Table 1).

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Table 1 — Hydromorphological characteristics of TraC waters
Assessment
Generic features Features assessed
Categories
MORPHOLOGY
1 Physiography
1a Planform (mouth width, coastal lagoon, estuary)
1b Artificial structures
1c Land claim
1d Beach nourishment
2 Connectivity
2a Seaward connectivity
2b Landward connectivity
2c Alongshore connectivity
3 Geology
3a Substrate
3b Bedform patterns
4 Biology
4a Disturbance to aquatic vegetation
4b Disturbance to natural biogenic reefs
4c Introduction of biota that form biogenic structures
HYDRODYNAMIC REGIME
5 Tidal regime
5a Tidal prism
6 Wave regime
6a Wave exposure
7 Water balance
7a Residence time/flushing rate
7b Freshwater discharge
8 Sediment dynamics
8a Sediment supply
Stratification or degree of
mixing
9a Salinity
9b Temperature
9c Stratification
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5.2 Defining hydromorphological units

Units for assessing TraC waters should be defined using morphological features, geographical units and

discontinuities in coastlines, water column characteristics, coastal cells, inputs of fresh water, and

dimensions. The aim should be to delimit manageable areas for hydromorphological assessment.

Coastal waters may be dynamic and long-shore boundaries should be identified. These can be defined at

various scales, depending on the purpose of the study. No one definition of the landward boundary of

coastal waters accurately fits all conditions. Highest Astronomical Tide limit provides a consistent and

definable landward boundary, although internationally recognized baselines are now used to delimit

the start of territorial waters. In non-tidal or micro-tidal systems, a locally agreed high water mark,

which allows for storm surges, will suffice.

The seaward boundary of coastal waters is usually defined geo-politically based on distance from the

accepted baselines — normally to the 12-mile limit although this has no scientific justification. For the

purpose of hydromorphological assessment, the seaward limit along active shorelines in coastal waters

is the boundary beyond which significant nearshore hydrodynamic changes (e.g. sediment transport)

cannot be detected. For rocky coasts, where such processes are less significant, a more pragmatic

seaward limit can be set, such as the 1 nautical mile boundary in the WFD.

For hydromorphological assessments of transitional waters, a “whole estuary approach” works well for

small and medium-sized estuaries. In large estuaries, geological constraints combined with greater

contrasts in wave energy dissipation can produce two or more distinctive “behavioural zones” within

the estuary. Transitional waters (except for non-tidal lagoons) where not constrained by artificial

structures, often do not have clear boundaries with surrounding habitats. However, their boundaries

need to be defined in a consistent way so that valid comparisons can be made. For the purpose of this

standard, the upstream limit of an estuary should be defined as the Normal Tidal Limit, but in non-tidal

estuaries the upstream limit should be the point beyond which there is no saline influence. The location

of a boundary at the seaward limit of transitional waters should take account of the particular

geography of each site. Often, geographical features such as deltaic sandbanks, narrow mouth entrances

(e.g. lagoons), or discontinuities (breaks) in the coastline create a locally agreed boundary, hence the

need for local expertise and agreement. In some areas and countries, consistency has been achieved

using a “bay closing line” across the mouth of an estuary although this is difficult to determine in wide-

mouthed, funnel-shaped, coastal plain estuaries.
5.3 Procedure for scoring

Annex A sets out guidance on how to allocate scores for each feature category. It contains two separate

procedures for scoring — using score band A with quantitative data, or score band B with qualitative

data. Score band A (which is used for some of the 23 features) is a 5-point scale (1 = lowest degree of

modification, 5 = highest degree of modification). Score band B is a 3-point scale (1, 3, 5; following the

same general approach as for score band A). Users should state which scores have been assigned based

on quantitative data and which on qualitative descriptions, as this determines the degree of confidence

in the assessment. This note should also be added to any maps produced that show the results of TraC

hydromorphological assessment. An attribute should be left unscored where the user is not confident in

allocating a score.

Where the majority of scores have been derived from 5-band scales users may wish to retain the

5 bands.
Where the majority have been derived from 3-band scales users may
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Questions, Comments and Discussion

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