physical science research: geomorphological impact and fluvial system response to the cumbria floods...

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