physical science research: geomorphological impact and fluvial system response to the cumbria floods...
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Physical Science Research:Geomorphological impact and fluvial system response
to the Cumbria floods November 2009
Jeff Warburton, Danny Donoghue (Durham University)
Andy Large, Andy Russell (Newcastle University)
Stuart Dunning (Northumbria University)
Structure:
•Background•Current Research•Upland impacts•Lowland impacts•Mapping Change•Challenges
Background: Recent upland flood events
Shetland, Scotland September 2003
North York Moors, England June 2005
Northern England January 2005
Northern England October 2008
Valley erosion and deposits
Flood extent image, 23 June 2005
Rollei ARSF NERC digital camera
From: Watkins and Whyte (2008) – ‘updated’
Cumbria floods – ‘flood rich’ periods
Ouse Bridge - Largest flood on ‘record’
Dissection & Gullying
Mass Movements & debris flows
Sheet & Wash Erosion
Suspended Load
Wind Erosion
Slope Deposits
Stream Course & Bank Erosion
Pipe erosion
Scar & Peat Margin Erosion
Bedload
Channel Sediments
Lakes & Reservoirs
HIL
LS
LO
PE
CH
AN
NE
L
Streambank
Solute & Flotation Load
storage
process
Background – contemporary sediment budgets
UPLAND
LOWLAND
Objectives:
1.Structured field inventory of the geomorphic impact on the River Derwent river corridor
2.Provide a rapid geomorphic assessment of the role of scour and sedimentation in the river
3.Identify areas of risk for remobilisation of flood-deposited sediments; delivery of hillslope sediments and hotspots of erosion
4.Compare post-flood field-derived data with pre-existing surveys to quantify/ areas of greatest geomorphic change
5.Work with stakeholders in designating catchment zones that are ‘at risk’ from erosion and sedimentation
Aim: to examine flood impacts the whole river corridor of the river Derwent from the headwaters, through Bassenthwaite Lake to the Lowland agricultural/urban catchment
Scale of river and catchment management
(Newson, 1992)
1.Survey headwater impacts - Coledale, Newlands and Borrowdale areas
2.Bassenthwaite Lake - collect a series of short cores and grab samples from the Lake and compared with a survey undertaken in 2008.
3.Lowland channel change in the floodplain downstream of Bassenthwaite Lake - focussing on ‘typical’ reaches e.g. Isel and Camerton.
4.Support field survey with low-level high-resolution aerial surveys carried out using a UAV (Unmanned Aerial Vehicle) - provide rapid repeat, high resolution aerial imagery and Digital Elevation models of key sites (cf. larger scale ARSF and EA remote sensing data).
Plan of Research:
Upland Impacts
Seathwaite, Borrowdale 2009
Coledale, 2009
Goldscope Valley, Northern Lake District 2009
Mapping elements
Source area 1
Runout
Source area 2
Runout
Debris fan
Map and sediment budget
Landslide erosion
518 m3
Deposition
400 m3
Sediment loss
118 m3
Completed inventory of erosion / deposition Coledale flood 2008
Shallow landslide
Landslide deposition
Surface wash
Sediment deposition
Stream erosion
Stream deposition
Dam pond deposition
Debris flow
Slope undercutting
Fan deposition
Torrent erosion
Channel erosion
Debris flows
Landslides
Slope undercutting
Footpath wash
Delivery to main fluvial system
Channel deposition
Debris flow fans
Landslide deposits
Slope wash deposit
Summary sediment budget (Coledale, 2008)
Values in t
817
183
195
102
7
189
933
92
97
7
14 %
Bassenthwaite Lake Coring and Sampling
Ouse Bridge & Herdwick Croft
Lowland Impacts
Ouse Bridge Gauging Station
Ouse Bridge
Isel Church
Sediment supply: landslides
Sediment supply: erosion of coarse gravel sediment
‘Hidden’ scour of river bed
New gravel bar: Downstream of Isel Hall
Downstream of A595 Bridge below Cockermouth
Flood debris
Sediment supply: localised scour around trees
Camerton
Sediment supply: erosion of river deposits
Sediment supply: localised bridge pier scour
Localised gouging and scour of cohesive flood plain sediment
Localised gouging and scour of cohesive flood plain sediment
Localised gouging and scour of cohesive flood plain sediment
Ground survey: ‘Reach-based’ assessments
Mapping flood limits
Mapping change – Airborne Remote Sensing
Downstream impacts - Workington
Papcastle
Future challenges / research problems?
1. Assembling an evidence base
a) Determining the sources of catchment sediment and linkages
b) Assessing the role of lakes in flood routing and timing
c) Investigate the impact of gravel management on flood impact
2. Determining whether current problems are ‘natural’ or human-driven
3. Recognising flood impacts are space and time specific
4. Establishing the ‘whole catchment’ context
5. Turning case studies into policy - impact