Presentation on theme: "Modelling catchment sediment transfer: future sediment delivery to the Carlisle urban area Tom Coulthard Jorge A. Ramirez Paul Bates Jeff Neal."— Presentation transcript:
Modelling catchment sediment transfer: future sediment delivery to the Carlisle urban area Tom Coulthard Jorge A. Ramirez Paul Bates Jeff Neal
Blue, flood outline before, Red flood outline after....
Project Aims/Summary To model sediment delivery from the Eden catchment and how this can affect flooding in Carlisle Using CAESAR, to model morphological change in the Eden river catchment and Carlisle reach Use different climate & discharge records to simulate impact of climate and land cover change Transfer updated DTM to Bristol for hydraulic modelling
What is CAESAR? Catchment or Reach based cellular model Models Morphological Change Hydrological model – Adaptation of TOPMODEL Hydraulic model – Simple 2d steady state flow model Sediment transport – Bedload, 9 fractions using Wilcock & Crowe eqtn. – Suspended sediment, multiple fractions Slope Processes – Slope failure (landslips) – Soil Creep
Main Tasks Two modelling tasks: – 1. Model sediment and water from catchments draining into Carlisle – 2. Model morphological changes in Carlisle reach
1. CAESAR catchment scale tasks Produce sediment output for the Eden river at Carlisle – Existing climate – Climate scenarios – Land cover change
Eden river sub-catchments 50m spatial resolution 6 sub-catchments Divisions coincide with flow gauges Km 25 Upper Eden Lower Eden Eamont Irthing Caldew Petteril Carlisle
Climate change: What we wanted to do... Use UKCP09 weather generator to predict future rainfall Use rainfall predictions as divers for the CAESAR morphological model Generate sediment yields (and updated DEMs) for futures.
Upper Eden Climate Eamont Lower Eden Irthing Petteril Caldew 0 200,000 400,000 600,000 0 200,000 400,000 600,000 0 200,000 400,000 600,000 Time, hours Cumulative rainfall, mm 0 100000 200000 0 100000 200000
75 year simulation 13 years of hourly rainfall repeated and amplified by climate factor – 13 years chosen as only continuous period across all catchments/raingauges – Climate factor increased by 10, 20 and 30% Record DEM’s and sediment outputs Catchment simulations
Petteril Caldew Lower Eden Irthing Eamont Upper Eden Catchment Sediment output 0 200,000 400,000 600,000 0 200,000 400,000 600,000 0 200,000 400,000 600,000 Time, hours 0 Cumulative sediment, m 3 0 1000000
2. CAESAR reach scale tasks Produce future bed elevations for the Eden reach at Carlisle: Determine how this affects flood inundation
Water inputs Cumulative Discharge ( m 3 /sec) Eden Caldew Petteril Time, hours 0 200,000 400,000 600,000 0 20000000 30000000 10000000 Eden 84% Caldew 11% Petteril 5% Hourly Discharge
Sediment inputs Cumulative sediment, m 3 0 1000000 0 200,000 400,000 600,000 0 200,000 400,000 600,000 0 200,000 400,000 600,000 Time, hours Petteril Caldew Lower Eden 83% 12% 5% Eden Caldew Petteril Hourly lumped sediment
Changes in bed elevation -6m(Deposition) 6m(Erosion) +30% +10% Baseline +20%
LISFLOOD-FP 0 11 Depth, m reference DTM +30% Model formulation with inertia (Bates et al., 2010) 2D channel and floodplain. Normal depth at boundary with slope 0.0006 mm -1 (Horritt et al., 2010)
Bed elevations affect on flood levels 3 (more flooding) - 2 Difference in maximum water elevation (new – original) Baseline +20% +30% ∆ max water depth, m +10% (less flooding)
Conclusions Morphological changes in the channel can have profound influences on inundation levels – relative to changes in flooding caused by climate change? Changes in flood level directly linked to erosion/deposition – Incision/aggradation alters conveyance Changes in channel pattern (cutoff) have a fairly profound affect on inundation patterns Relationship between discharge increase and changes in sediment yield is very site specific.. – Hard to apply a generic rule to all reaches
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