Trinity Broads – Rollesby Broad: Rollesby Sailing Club water plant cutting notice
Record of Habitats Regulations Assessment for The Broads SAC under Regulation 23 of The
Conservation of Habitats and Species Regulations 2010
Record of judgement of consent under Section 28E(3)(a) Wildlife and Countryside Act 1981 (as amended
and inserted by section 75 and Schedule 9 of the Countryside and Rights of Way Act 2000)
1.
Site of Special Scientific Interest
Trinity Broads
2.
Special Area of Conservation (SAC)
The Broads
3.
Owner
Northumbrian Water Ltd.
Northumbria House
Abbey Road
Pity Me
Co Durham
DH1 5FJ
4.
Occupier
Rollesby Broad Sailing Club
Burghwood Road
Ormesby St. Michael
Norfolk
NR29 3LT
5.
Date of notice
original - January 6th 2011; amended to include monitoring – February 21st 2011
6.
Location of project
Part of Rollesby Broad, unit 24 within Trinity Broads SSSI.
7.
Grid reference
TG61149
8.
Brief description of project
To cut an area of Elodea canadensis and/ or Elodea nuttallii within Rollesby Broad to enable the
continuation of sailing through the summer and early autumn months to a specified depth.
9.
Detail of project
The operation set out in the notice of February 21st 2011 included:
Project
• to cut all tall-growing Elodea canadensis and/ or Elodea nuttallii in an area of c.9.3hectares
within Rollesby Broad (c. 35% of Rollesby Broad area);
• a variable non-intervention area between the cutting area and the broad shore, with a minimum
distance of 15 metres;
• a cutting depth up to a maximum of 1.3m from the water surface;
• a cutting period between mid July and the end of September; based on 2010 growth when Elodea
was a problem between mid July and the end of October, cutting would be anticipated in late July/
early August, and again in September, as required;
• plant material would be cut and removed using a water plant harvester;
• removed plant material would be put at the rear of the sailing club’s car-park (outside of the SSSI)
to dry out, and then removed or spread within the adjacent woodland area;
• using 2011 as a trial to determine effectiveness.
Triggers for cutting
• Elodea less than 1.30m below surface at 50% of the standard Trinity sample locations within the
proposed water plant cutting area, assessed in mid July, and subsequently as required;
• Water clarity: Secchi disk reading of at least 1.00m at 90% of sample locations; method of data
collection to be guided by Trinity Project Officer;
• Aquatic plant community extent, composition and structure should be consistent between cut and uncut
areas, as informed by the Trinity Broads Partnership water plant survey in June and August and
discussion based on observations at the time of proposed cutting.
Conditions for cutting
• The boundaries of the proposed water plant cutting area should be identifiable with GPS locations and
small marker buoys as required;
• Discrete areas within the proposed water plant cutting area with characteristic species as dominant
(Chara virgata, Chara globularis, Chara vulgaris, Lemna minor, Lemna trisulca, Potamogeton
berchtoldii, Potamogeton crispus, Potamogeton friesii, Potamogeton pusillus, and Ranunculus
circinatus recorded in 2009 and 2010) at or near the surface should be avoided, if possible, as agreed
between the partnership and the sailing club;
• If Najas marina or Potamogeton trichoides are found to occur within the proposed water plant cutting
area on Rollesby Broad they must be avoided;
• Cutting must only take place when lake surface conditions avoid any displacement of plants occurring
due to vertical movement of the water plant cutter;
• Cutting must be suspended if significant uprooting of plants and/ or significant sediment plumes occur
during cutting;
• Cut material must be removed from the water body.
Ongoing monitoring
Water plants
• Existing Trinity Broads Partnership water plant monitoring to continue during June and August,
recording the current range of parameters, using the existing sample points.
Otter
•
All observations of otter to be recorded.
Non-breeding wildfowl
• WeBS counts to continue monthly, using the existing count sections.
10. Operations likely to damage (OLDs)
The following ‘operations likely to damage’ are relevant to the proposal:
7
11
26
Dumping, spreading or discharge of any materials.
The destruction, displacement, removal or cutting of any plant or plant remains, including
tree, shrub, herb, hedge, dead or decaying wood, reed, sedge and turf.
Use of vehicles or craft likely to disturb features of interest.
11. Notified interest features
The table below shows all features for which Trinity Broads SSSI is notified, indicating those that are SSSI
features (nationally important) and those which are SAC features (internationally important). There is then
an assessment of whether the features need to be considered against this proposal, with three potential
outcomes:
•
•
•
The feature does not need to be considered;
The SAC feature needs to be assessed following the Habitats Regulations processes;
The SSSI feature needs to be assessed following CRoW Act 2000 processes.
Notified interest feature
Natural eutrophic lakes with Magnopotamion or
Hydrocharition-type vegetation
Hard oligo-mesotrophic waters with benthic
SSSI/ SAC
feature
SAC
Consider against
project
SAC
Comments
Potential
feature.
Potential
for
direct
impact
on
for
direct
impact
on
vegetation of Chara species
Vascular plant assemblage (standing waters)
Najas marina
Holly-leaved naiad
Potamogeton trichoides Hair-like pondweed
M22 Juncus subnodulosus/ Cirsium palustre fen
meadow
S2 Cladium mariscus swamp and sedge-beds
SSSI
SAC
SSSI
S24 Phragmites australis/ Peucedenum palustre
tall-herb fen
Vascular plant assemblage (fens)
Peucedenum palustre Milk parsley
Cicuta virosa
Cowbane
Aggregations of non-breeding birds – marsh
harrier
Aggregations of non-breeding birds – bittern
SSSI
SSSI
SSSI
SSSI
Vertigo moulinsiana – Desmoulin’s whorl-snail
SAC
Invertebrate assemblage – permanent wet mire
SSSI
W2 Salix cinerea/ Betula pubescens/ Phragmites
australis woodland
W5 Alnus glutinosa/ Carex paniculata woodland
SSSI
SAC
Lutra lutra Otter
SAC
Aggregations of breeding birds – pochard
SSSI
Aggregations of non-breeding birds – pochard
SSSI
Aggregations of breeding birds – shoveler
SSSI
Aggregations of non-breeding birds – shoveler
SSSI
Aggregations of breeding birds – tufted duck
SSSI
Aggregations of non-breeding birds – tufted duck
SSSI
Assemblages of breeding birds – lowland open
waters and their margins
SSSI
feature.
Potential
feature.
for
direct
impact
Terrestrial feature not directly
indirectly impacted by proposal.
Terrestrial feature not directly
indirectly impacted by proposal.
Terrestrial feature not directly
indirectly impacted by proposal.
Terrestrial feature not directly
indirectly impacted by proposal.
on
or
or
or
or
Marsh
harrier
use
terrestrial
components of the site.
Potential for indirect effects of
disturbance, but past data show that
bittern occurs primarily in the winter
months and mainly on the other
Trinity Broads.
A species of the littoral and
terrestrial swamp communities, not
directly or indirectly impacted by
proposal.
Species assemblage associated with
terrestrial fen communities not
directly or indirectly impacted by
proposal.
Terrestrial feature not directly or
indirectly impacted by proposal.
Terrestrial feature not directly or
indirectly impacted by proposal.
Potential for indirect effects of
disturbance, and alteration of fish
community.
Potential for indirect effects of
disturbance, but breeding will have
concluded by late July/ early August
when first water plant cut proposed.
Indirect effects of removal of food
source (plant material & associated
fauna) has potential for impact on
feature.
Potential for indirect effects of
disturbance, but breeding will have
concluded by late July/ early August
when first water plant cut proposed.
Indirect effects of removal of food
source (plant material & associated
fauna) has potential for impact on
feature.
Potential for indirect effects of
disturbance, but breeding will have
concluded by late July/ early August
when first water plant cut proposed.
Indirect effects of removal of food
source (plant material & associated
fauna) has potential for impact on
feature.
Potential for indirect effects of
disturbance, but breeding will have
concluded by late July/ early August
when first water plant cut proposed.
12. Assessment of SAC features
The following are the SAC features that need to be considered under Regulation 23 of The Conservation of
Habitats and Species Regulations 2010
Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation
Hard oligo-mesotrophic waters with benthic vegetation of Chara species
Lutra lutra Otter
Natural England’s view is that the project described above, under section 9, is likely to have a significant
effect on the features listed above. The likely significant effects are:
• Direct impact on the aquatic macrophyte communities that form a constituent part of the two
SAC lake features by removal of material, potentially leading to changes in extent, composition
and structure of the features;
• Indirect impacts on the SAC lake features through alteration of the ecosystem balance, potentially
leading to changes in extent, composition and structure of the features;
• Disturbance of otter.
Following this judgement about likely significant effects, it is Natural England’s view that the project is
not necessary for the conservation of the site features.
It is therefore necessary to carry out an Appropriate Assessment as required by Regulation 23. This
requires that the project causes ‘no adverse effect on the site integrity’.
Appropriate Assessment
Rollesby Broad was assessed using Common Standards Monitoring (CSM) as part of Natural England’s
ongoing programme of condition assessments on February 2nd 2009. It was judged as being ‘unfavourable
recovering’ with the following comment:
“The Trinity Broads have shown a continual improvement over a number of years. This in part may be due
to climatic conditions (two wet summers). All lake basins, except Filby are currently meeting all the
conservation objective attributes. Accordingly these have been recorded as unfavourable recovering.
However a number of factors mean that the site is not in a stable condition, and there is a high risk of
deterioration and failure of targets in future years. These risk factors involve the high, stable levels of
phosphorus within the system, the impact of a drought summer and the summer drawdown of water
levels.”
The CSM assessment is made against the conservation objectives for the relevant feature. The competent
authority (in this case Natural England) is required to make an appropriate assessment of the implications
for the site in view of that site’s conservation objectives. The appropriate assessment of the project against
the conservation objectives for the relevant features is shown below.
Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation
Hard oligo-mesotrophic waters with benthic vegetation of Chara species
Effect of project
Attribute & site-specific targets
Indicators of local distinctiveness
Maintain distinctive elements (e.g. rare
plant or invertebrate species, habitat
features) at current extent/levels within
Ormesby Broad.
Not applicable.
Restore distinctive elements (e.g. rare
plant or invertebrate species, habitat
features) at historic extent/levels within
the remaining four Broads.
Rollesby Broad has shown continued improvement in the extent, composition and
structure of the SAC lake features since the conservation objectives were written on
9/2/2009. No distinctive elements are identified that will not be addressed through
other attributes listed below.
Lake substrate
Maintain natural shoreline – no more than
5% of shoreline should be heavily
modified.
Maintain
substrate.
natural
and
characteristic
Sediment load
Maintain natural sediment load.
The project will have no effect on the shoreline.
Water plant cutting has the potential to disturb lake substrate if plants are uprooted.
The maximum proposed cutting depth of 1.3m. should avoid this from occurring. The
conditions for cutting outlined in the notice should avoid substrate being disturbed.
Cutting will be suspended if sediment disturbance occurs.
Water plant cutting has the potential to disturb lake substrate if plants are uprooted.
The maximum proposed cutting depth of 1.3m. should avoid this from occurring. The
conditions for cutting outlined in the notice should avoid substrate being disturbed.
Cutting will be suspended if sediment disturbance occurs.
Vegetation composition: macrophyte
community
Natural eutrophic lakes
i)
Presence of at least 6 of the
characteristic species listed for
this
feature,
and
one
Potamogeton species (except
where valid reasons suggest
otherwise).
In 2009, Rollesby Broad contained 8 characteristic species, namely Chara globularis,
Chara vulgaris, Lemna minor, Lemna trisulca, Potamogeton crispus, Potamogeton
friesii, Potamogeton pusillus, and Ranunculus circinatus.
In 2010, Rollesby Broad contained 9 characteristic species, namely Chara virgata,
Chara globularis, Chara vulgaris, Lemna trisulca, Potamogeton berchtoldii,
Potamogeton crispus, Potamogeton friesii, Potamogeton pusillus, and Ranunculus
circinatus. All except Chara vulgaris and Ranunculus circinatus were present in the
proposed cutting area.
None of these species are specific to the area where water plant cutting is proposed, so
their presence will be perpetuated within Rollesby Broad. There is no evidence to
suggest that their presence will be diminished by water plant cutting.
ii)
6 out of 10 sample spots (boat
or wader survey) should
include
at
least
one
characteristic species.
In 2009, 96% of sample points in Rollesby Broad included at least one characteristic
species present (see list above). In 2010 this rose to 100%. Early characteristic species
will persist in the cut area; it is unlikely that characteristic species would disappear
from sample sites due to the height of the cut, though relative composition and mean
weight may change; if all characteristic species disappeared from all sample points in
the cut area, 62% of samples across the Broad would still meet this attribute. At least
65% of the Broad will remain uncut. Sample points will continue to be monitored,
thereby providing data on any changes that occur. Only areas of the proposed cut area
where Elodea is within the top 1.3m of the water column, will be cut.
Based on the August data for 2009 and 2010, the following observations are made on
characteristic species:
Chara virgata – not noted in the 2009 survey; the mean weight of samples from the
proposed cut area in 2010 constituted 2.7% of the total of samples from Rollesby
Broad, regardless of whether there was significant growth of Elodea spp. or not; this
species seems to be better represented in the shallower areas of Rollesby Broad outside
the proposed cutting area.
Chara globularis – the mean weight of samples from the proposed cut area constituted
(2010 – 8.1%) (2009 - 16.0%) of the total of samples from Rollesby Broad; if this was
limited to only sites where there was significant growth of Elodea spp. this reduces to
(2010 – 7.5%) (2009 - 1.2%); this species seems to be better represented in the
shallower areas of Rollesby Broad outside the proposed cutting area.
Chara vulgaris - the mean weight of samples from the proposed cut area constituted
(2010 – 0%) (2009 - 45.7%)of the total of samples from Rollesby Broad; if this was
limited to only sites where there was significant growth of Elodea spp. this reduces to
(2009 - 0.1%); this species seems to be better represented in the shallower areas of
Rollesby Broad outside the proposed cutting area.
Lemna minor – not encountered in the proposed cut area in either year.
Lemna trisulca – a minor component throughout Rollesby Broad that due to its ecology
will be largely unaffected by cutting; more restricted to the shallower margins.
Potamogeton berchtoldii – not encountered in the 2009 survey; encountered in one
sample in the 2010 survey, outside the proposed cut area.
Potamogeton crispus – encountered in one sample within the proposed cut area in the
June survey, but no records in the August survey in both 2009 and 2010.
Potamogeton friesii – a reduction from a mean weight across the Broad of (2010 –
3707g) (2009 – 5754g) in the June survey to (2010 – 269g) (2009 – 757g) in the August
survey, indicating the decline that shows this species to be less of a problem for sailing;
the mean weight of samples from the proposed cut area constituted (2010 – 33.8%)
(2009 - 30.6%) of the total of samples from Rollesby Broad; if this was limited to only
sites where there was significant growth of Elodea spp. this reduces to (2010 – 33.8%)
(2009 - 4.5%).
Potamogeton pusillus – a reduction from a mean weight across the Broad of (2010 –
23812g) (2009 – 422g) in the June survey to (2010 – 2745g) (2009 – 47g) in the August
survey, indicating the decline that shows this species to be less of a problem for sailing;
the mean weight of samples from the proposed cut area constituted (2010 – 54.3%)
(2009 - 8.5%) of the total of samples from Rollesby Broad; if this was limited to only
sites where there was significant growth of Elodea spp. this reduces to (2010 – 17.7%)
(2009 - 2.1%).
Ranunculus circinatus – present, but no data from sample points in both years.
iii) There should be no loss of
characteristic species recorded
from the site.
None of the characteristic species are specific to the area where water plant cutting is
proposed, so their presence will be perpetuated within Rollesby Broad. There is no
evidence to suggest that their presence will be diminished by water plant cutting.
Hard oligo-mesotrophic waters
iv) Characteristic species should
be present.
In 2009, Rollesby Broad contained 1 characteristic species, namely Chara globularis; in
2010 both Chara virgata and Chara globularis were present; Chara vulgaris was
present in both years, but is not a characteristic species of this feature, but an associate.
Chara virgata and Chara globularis are not specific to the area where water plant
cutting is proposed, so their presence will be perpetuated within Rollesby Broad.
v)
7 out of 10 sample spots (boat
or wader survey) should
include
at
least
one
characteristic species.
Vegetation
composition:
negative
indicator species
Non-native species should be absent or
present at low frequency.
In 2009, 73% of sample points in Rollesby Broad included Chara globularis; in 2010,
88% of sample points in Rollesby Broad included Chara virgata and Chara globularis.
It is unlikely that this species would disappear from sample sites due to the height of the
cut, though relative composition and mean weight may change; (see species description
above)
Non-native invasive alien species of particular concern are not present in the Trinity
Broads. The water plant cutting proposal will not alter this situation.
This attribute states that occurrence of Elodea nuttallii or Elodea canadensis at >40%
frequency in unproductive waters, and >50% frequency in more productive waters, is
indicative of unfavourable condition. In 2010 frequency in the August survey was
100%. Therefore, the proposed water plant cutting may contribute to improved delivery
of this attribute.
Cover of benthic and epiphytic
filamentous algae should be less than
10%.
Filamentous algae were not present in the proposed cut area in 2009. Water plant
cutting should not increase the cover of algae.
Cutting may encourage a switch to algal dominance – something which this site is at
risk of, being a eutrophic shallow lake which has only recently been recolonised by
macrophytes. If the macrophytes take too great a hit, then algae can become dominant
and eventually exclude the remaining macrophytes though light competition. Once this
happens it is hard to get the macrophytes back as both algal-dominated and plantdominated states are perpetuated by a host of positive feedback mechanisms (e.g.
macrophytes provide refugia for zooplankton which feed on the algae to keep algae
down and allow light to penetrate and allow submerged macrophyte growth). The
monitoring in place will identify whether there is a shift in this balance, and time limit
will allow action to be taken.
Vegetation composition: macrophyte
community structure
Characteristic zones of vegetation should
be present.
Maximum depth distribution should be
maintained.
At least the present structure should be
maintained.
Water quality
Stable nutrient levels appropriate to lake
type.
Mean
annual
total
phosphorus
concentration less than target for
appropriate lake type (see Table 1 below).
The proposed cut area will potentially reduce aquatic macrophyte growth to 1.3m
below surface over a maximum of 35% of Rollesby Broad. Based on hydroacoustic
observations in 2010, this would have resulted in 51.4% of the potential cutting volume
being cleared of plants, though this does not indicate species and therefore the volume
of Elodea may have been less, and also the area where plants were causing an issue at
the surface would have been less (Williams, 2011). The two proposed cuts would affect
the structure temporarily across the cut area. This attribute focuses on characteristic
species – the fine-leaved Potamogeton spp. tend to die back later in the season and will
therefore be largely unaffected by the proposal; charophytes have largely been located
in the shallower areas of the site, and do not currently occupy the upper area of the
water column in the deeper parts of the broad. More permanent structural changes may
occur due to the cutting.
Nutrient levels should not be altered by water plant cutting, unless sediment is disturbed
through cutting operations (see sediment above).
Stable pH/ANC values appropriate to lake
type.
pH/ANC levels should not be altered by water plant cutting.
Adequate dissolved oxygen levels for
health of characteristic fauna.
Dissolved oxygen levels should not be altered by water plant cutting.
No excessive growth of cyanobacterial or
green algae.
Hydrology
There should be a natural hydrological
regime.
Cyanobacterial or green algae should not be altered by water plant cutting.
No loss of marginal vegetation
Water plant cutting will not impact on marginal vegetation; there will be a minimum
non-intervention zone of 15m between the swamp fringe and the proposed cut area.
Water plant cutting will not impact upon the natural hydrological regime.
Lutra lutra Otter
There have been regular sightings of otter on Rollesby, Lily and Ormesby Little Broads, with young
observed in 2009. A lot of the activity is near the channels between Rollesby and Lily and Rollesby and
Ormesby Little towards the southern end of Rollesby Broad. Spraints have been found in a number of
locations, including Rollesby sailing club and under Rollesby bridge.
The proposed water plant cutting could only cause minor disturbance to the otter population due to:
• the main area of otter activity at Rollesby Broad being observed away from the proposed cutting
area;
• the proposed water plant cutting occuring during the daytime;
• the length of cutting period being short;
• alternative low disturbance areas for otters to use.
The proposed water plant cutting would not adversely affect the food supply of the otter population due to:
• the 65% of the broad that would remain uncut;
• the relative health of the fish population prior to significant growth of aquatic macrophytes and
particularly Elodea;
• the health of otter populations in other broads where aquatic macrophyte growth is poor.
Ongoing monitoring will allow significant changes in fish populations and otter populations to be assessed.
Levels of activity (e.g. sightings, holts, spraints, footprints) will be noted and taken account of prior to the
proposed water plant cutting operations.
Conclusion for SAC features
The analysis against the conservation objectives above indicates that the proposed water plant cutting will
not lead to a loss of characteristic species across Rollesby Broad based on the data from 2010, or an ability
to meet the cover requirements of the objectives. The maximum area where cutting would occur
constitutes 35% of Rollesby Broad. Of this area, the 2010 data suggests that about 51.4% of the potential
cutting volume would involve the cutting of aquatic plants. This could be further reduced, by focusing on
areas where Elodea is the problem and where it is impeding sailing use.
The identification of triggers for cutting and the ongoing monitoring will allow Natural England to judge
the effects of the project on the SAC lake features. The limit of the cutting to a single year will allow
Natural England to review the data and judge against any future proposals.
Natural England concludes that there is no evidence to suggest that the conservation objectives will not
continue to be met for the SAC features. The triggers for action, conditions for cutting, ongoing
monitoring, and time limit for the project allow Natural England to conclude that there will be no adverse
effect on site integrity.
13. Assessment of SSSI features
The following are the SSSI features that need to be considered under Section 28E(3)(a) Wildlife and
Countryside Act 1981 (as amended and inserted by section 75 and Schedule 9 of the Countryside and
Rights of Way Act 2000).
Vascular plant assemblage (standing waters) - Najas marina (Holly-leaved naiad), Potamogeton trichoides (Hair-like pondweed)
Aggregations of non-breeding birds – pochard
Aggregations of non-breeding birds – shoveler
Aggregations of non-breeding birds – tufted duck
For SSSI features, Natural England needs to determine whether the proposal is compatible with furthering
the conservation and enhancement of the special interest of the site.
Vascular plant assemblage (standing waters)
Najas marina (Holly-leaved naiad)
Potamogeton trichoides (Hair-like pondweed)
Najas marina has only been recorded on Ormesby Broad during 2009 and 2010. It has not been recorded
from Rollesby Broad. If this species was encountered during survey work, its location could be avoided.
Potamogeton trichoides has only been recorded in the Trinity Broads once in 2002 on Ormesby Broad. If
this species was encountered during survey work, its location could be avoided.
Aggregations of non-breeding birds
Bird count data has been assessed for the whole of the Trinity Broads, and compared with the totals for
Rollesby Broad, and the two count sections that largely coincide with the proposed water plant cutting area
(R2/ R3). Wintering bird numbers are usually assessed on 5 year peak means; however, 2005 and 2006
data are incomplete and therefore the analysis has been limited to the four years 2007 – 2010. November
and December counts for 2006 are used to calculate the average winter numbers for 2006/07.
Pochard
Month
November 2006
December 2006
January
February
March
April
May
June
July
August
September
October
November
December
TBs
24
44
49
107
42
43
34
21
70
47
5
31
27
8
Avg. (Nov – Feb)
56.0
4 year winter avg.
% of Trinities
4 year peak mean
% of Trinities
2006/ 2007
RB
R2/3
0
0
0
0
2
2
10
0
1
0
0
0
1
0
0
0
0
0
38
38
0
0
14
10
0
0
0
0
3.0
0.5
TBs
66.4
2006 - 2010
RB
R2/3
13.9
7.6
20.9
11.4
TBs
159
2007 - 2010
RB
R2/3
58
55
36.5
34.6
2008
RB
R2/3
30
81
33
13
0
3
10
5
11
49
37
29
5
1
0
2
0
0
6
1
4
0
3
3
5
0
0
0
0
0
0
1
0
0
0
3
36.5
1.5
1.3
TBs
2009
RB
R2/3
71
35
25
23
10
21
6
1
92
14
48
0
12
9
2
10
4
2
1
0
85
2
0
0
0
1
0
0
2
0
0
0
65
2
0
0
43.0
6.8
1.0
TBs
2010
RB
R2/3
357
116
117
13
1
5
14
7
42
20
47
164
110
67
26
1
0
0
3
1
0
4
4
23
110
0
1
0
0
0
3
1
0
0
2
0
130.2
44.3
27.5
TBs
n.b. TBs = Trinity Broads (whole site); RB = Rollesby Broad only; R2/3 = two count sections on Rollesby
Broad that largely coincide with proposed cut area; counts shaded green indicate the peak count for each
counting area during the year; counts scored out indicate incomplete counts.
GB threshold
International threshold
595
3500
5 year peak mean 1987 – 1992
119
(complete 5 years of data prior to notification)
Peak count 1996
Peak count in preceding 10 years 1996
149
281
(basis for notification)
(basis for notification)
The following observations can be drawn from the recent data for pochard:
• The peak mean count has increased slightly since pre-notification; peak numbers are reasonably
consistent other than in the first winter period of 2010 when severe weather persisted;
• Rollesby Broad can provide an important contribution to the Trinity Broads population, such as in
2009 and 2010;
• When reasonable numbers occur in Rollesby Broad, R2/R3 usually play an important role;
• Numbers have not changed significantly since the period before there was significant macrophyte
growth;
• The pochard is generally sensitive to disturbance and prefers to stay a good distance away from
the water margins; they mainly feed in freshwater by diving, although they will occasionally
dabble in shallower water; they generally feed between 1 and 3 metres in depth; they mainly feed
on aquatic plants, with some molluscs, insects and small fish also taken; they often feed at night;
•
•
A proportion of the food source will still be available to pochard following water plant cutting; a
cutting height of 1.3m. below the water surface will allow some of the accessible feeding area to
remain intact; water plant cutting may lead to changes of composition, structure and extent of
macrophyte communities that may impact on wildfowl populations;
Continued monitoring will identify any significant changes in numbers and/or distribution that
could be attributed to water plant cutting.
Tufted duck
Month
November 2006
December 2006
January
February
March
April
May
June
July
August
September
October
November
December
TBs
285
286
187
211
37
178
91
21
128
97
194
506
152
474
Avg. (Nov – Feb)
242
4 year winter avg.
% of Trinities
4 year peak mean
% of Trinities
2006/ 2007
RB
R2/3
44
29
23
10
53
13
24
10
4
0
25
16
1
0
0
0
15
0
3
3
59
53
100
64
67
2
157
32
36
16
TBs
416
2006 - 2010
RB
R2/3
65
25
15.6
6.0
TBs
586
2007 - 2010
RB
R2/3
151
74
25.8
12.6
2008
RB
R2/3
418
424
275
300
16
35
149
151
179
399
689
778
91
91
27
34
0
15
44
0
68
57
10
36
34
28
9
14
0
0
3
0
20
42
0
29
439
113
31
TBs
2009
RB
R2/3
450
557
528
359
40
32
219
81
365
241
585
0
61
26
153
36
2
2
14
0
195
25
152
0
11
8
41
0
2
0
6
0
105
6
123
0
619
33
12
TBs
2010
RB
R2/3
309
191
459
423
56
75
319
185
258
325
381
476
29
54
162
10
0
5
15
0
68
124
58
25
0
0
60
0
0
0
3
0
68
35
28
0
362
78
41
TBs
n.b. TBs = Trinity Broads (whole site); RB = Rollesby Broad only; R2/3 = two count sections on Rollesby
Broad that largely coincide with proposed cut area; counts shaded green indicate the peak count for each
counting area during the year; counts scored out indicate incomplete counts.
GB threshold
International threshold
901
1200
5 year peak mean 1987 – 1992
171
(complete 5 years of data prior to notification)
Peak count 1996
Peak count in preceding 10 years 1996
158
209
(basis for notification)
(basis for notification)
The following observations can be drawn from the recent data for tufted duck:
• The peak mean count has increased significantly since pre-notification, from a 5-year peak mean
(1987-92) of 171 to a 4-year peak mean of 586 (2007-10);
• The peak contribution of Rollesby Broad is reasonably consistent, with the highest count of 195
recorded in September 2009;
• Tufted duck clearly utilise the whole system, leading to variability in the numbers recorded on
Rollesby Broad in the context of the site; during the highest count of 778 in December 2008, only
36 were recorded on Rollesby;
• Notification numbers of tufted duck would be maintained in the Trinities even without the
contribution of Rollesby Broad;
• When reasonable numbers occur in Rollesby Broad, the contribution of R2/R3 is variable;
• Numbers appear to have responded to significant macrophyte growth; whilst the plant material
does not constitute the main food source, there would appear to be a correlation with the
invertebrate prey of the tufted duck and macrophyte growth;
•
•
•
The tufted duck takes much more animal matter consisting of molluscs, insect larvae and
crustaceans than pochard, with relatively small amounts of vegetable matter and seeds being
eaten; the food is usually gleaned from the benthic layer of lakes at a depth of 1-3 metres;
A proportion of the food source will still be available to tufted duck following water plant cutting;
a cutting height of 1.3m. below the water surface will allow some of the accessible feeding area to
remain intact; water plant cutting may lead to changes of composition, structure and extent of
macrophyte communities that may impact on wildfowl populations;
Continued monitoring will identify any significant changes in numbers and/or distribution that
could be attributed to water plant cutting.
Shoveler
Month
November 2006
December 2006
January
February
March
April
May
June
July
August
September
October
November
December
TBs
9
26
0
27
8
5
0
0
0
0
0
4
0
100
Avg. (Nov – Feb)
15.5
4 year winter avg.
% of Trinities
4 year peak mean
% of Trinities
2006/ 2007
RB
R2/3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3
0
0
0
0
0
0
0
TBs
47.8
2006 - 2010
RB
R2/3
0.5
0.2
1.0
0.4
TBs
205.0
2007 - 2010
RB
R2/3
59.0
57.0
28.8
27.8
2008
RB
R2/3
51
29
338
87
0
0
0
25
71
0
17
159
51
0
226
76
0
0
0
0
0
0
0
4
0
0
220
3
0
0
0
0
0
0
0
0
60.0
17.0
0
TBs
2009
RB
R2/3
162
25
0
4
0
0
0
0
5
4
0
0
1
0
0
0
0
0
0
0
5
0
0
0
0
0
0
0
0
0
0
0
5
0
0
0
90.8
1.3
0
TBs
2010
RB
R2/3
12
63
4
4
0
0
0
2
1
11
0
220
2
0
0
0
0
0
0
0
1
0
0
0
2
0
0
0
0
0
0
0
1
0
0
0
25.0
0.7
0.7
TBs
n.b. TBs = Trinity Broads (whole site); RB = Rollesby Broad only; R2/3 = two count sections on Rollesby
Broad that largely coincide with proposed cut area; counts shaded green indicate the peak count for each
counting area during the year; counts scored out indicate incomplete counts.
GB threshold
International threshold
5 year peak mean 1987 – 1992
Peak count 1996
Peak count in preceding 10 years 1996
148
400
65
92
192
(complete 5 years of data prior to notification)
(basis for notification)
(basis for notification)
The following observations can be drawn from the recent data for shoveler:
• The peak mean count has increased significantly since pre-notification, from a 5-year peak mean
(1987-92) of 65 to a 4-year peak mean of 205 (2007-10);
• The peak contribution of Rollesby Broad is reasonably consistent, at a very low level of 2-5; the
clear exception was the count of 226 in March 2008 – as this is so different to the normal
contribution of Rollesby during peak counts, it suggests a significant displacement from the part
of the system that usually holds the highest numbers;
• The contribution of R2/R3 is usually tiny, aside from the exception noted above;
• Notification numbers of shoveler would be maintained in the Trinities even without the
contribution of Rollesby Broad;
• Numbers appear to have responded to significant macrophyte growth; the nature of shoveler
ecology means that they will tend to spend most of their time feeding in the shallower margins;
•
•
•
Shovelers feed by dabbling for plant food, often by swinging their bills from side to side and
using the bill to strain food from the water; they also eat molluscs and insects, particularly during
the breeding season; large groups often feed together and it is believed that their actions stir the
water and disturb more food;
The food source will still be available to shoveler following water plant cutting; shoveler numbers
in the Trinities will be maintained if water plant cutting takes place, due to their preference for
feeding in the shallower margins; water plant cutting may lead to changes of composition,
structure and extent of macrophyte communities that may impact on wildfowl populations;
Continued monitoring will identify any significant changes in numbers and/or distribution that
could be attributed to water plant cutting.
Conclusion for SSSI features
The aquatic species of the vascular plant assemblage will be conserved.
Non-breeding populations of pochard, tufted duck and shoveler will be conserved if water plant cutting
were to take place.
The identification of triggers for cutting and the ongoing monitoring will allow Natural England to judge
the effects of the project on the SSSI features. The limit of the cutting to a single year will allow Natural
England to review the data and judge against any future proposals.
Natural England concludes that there is no evidence to suggest that the conservation objectives will not
continue to be met for the SSSI features, particularly given the fact that wintering pochard, tufted duck and
shoveler numbers have increased significantly since notification.
14. Overall conclusion
Natural England concludes that there will be no adverse effect on the SAC features, and that the SSSI
features will be conserved.
The triggers for action, conditions for cutting, monitoring, and time limit for the project provide Natural
England with the safeguards to ensure that features are protected and allows ongoing monitoring of any
effects.
In the light of the above, Natural England gives consent to the notice of February 21st 2011.