River Derwent Restoration

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River Derwent Restoration
Concepts

Name Liz Chalk (Environment Agency) & Simon Christian (Natural
England)

Date October 2010

River Derwent SSSI

River Derwent SSSI

Designated for:

Lowland river profile

Floral interest

Fish communities

Invertebrates

Breeding birds

Otters


River Derwent SSSI

Management and
modification has led to
current unfavourable
condition

Restoration planning linking physical
processes to ecology of SSSI

Walkover survey

Desk
-
based
assessment

Identify key
issues


Workshops on reach
-
based
solutions

Potential reach restoration measures

Investigate the feasibility of
removing or modifying
Kirkham Weir, modifying
the operation of the sluice,
or replacing the fish pass

Manage sediment input
from field drains and
erodible soils

Undertake selective
vegetation management to
prevent overshading

Sedimentation

What is the issue?

The inwash of fine
sediments from the wider
catchment along SSSI

Sedimentation

What are the potential
solutions?

Adjust land management
& ditch maintenance
regime

Introduce buffer strips

Restrict stock access to
banks

Environmental
Stewardship

Control invasive plants



Giant hogweed

Distribution widespread
out
-
competing native flora

On die back can cause soil
erosion and entry into river

Control using glyphosate

Issue of overshading & lack of bank top
and channel shelter & shading

Overshading in some places & lack of
bank top and channel shelter and shading

What are the potential
solutions?

Sympathetic tree &
shrub management

Non
-
native plant
management

Bank re
-
profiling

Creation of aquatic
ledges

Weirs & barrage in the river channel

What are the issues?

Series of physical
barriers

Effect river levels &
velocities


Cause sediment build
up upstream

Restrict fish movement


Weirs & barrage in the river channel

What are the potential
solutions?

Remove

Modify e.g. lamprey ramp

Alter operation e.g.
sluices, navigation lock
operation, lamprey ramp

Fish pass

Staged approach taking
account of constraints,
evidence & scope for
multiple benefits


Channelisation and floodplain
disconnection

What are the issues?

Straightened, uniform
channel, over
-
wide and
over
-
deep with steep banks

Embankments separate river
from its floodplain

Causes reduced storage of
water and sediment in
floodplain and increased
flows and higher sediment
load in river.

River deposits sediment to
try to regain its natural
profile.

Restoration principles

Integrated approach setting
out the direction for
involvement of local people
in its realisation

Recognise constraints and
balances, particularly in
current economic climate

Short, medium & long term
timescales

Looking for multiple benefits
e.g. SSSI, flood risk, land
management, tourist
economy and cost effective
ways of working together to
make savings

Looking to link initiatives, at
catchment and landscape
scale to reduce diffuse
pollution and encourage
water storage upstream