SWOT ST MODEL INTER-COMPARISON
LISFLOOD-FP: Preliminary Results

Kostas Andreadis

Study area

arkansas.png Arkansas River basin

Model description

  • LISFLOOD-FP, a raster-based hydrodynamic model
  • Adaptive time stepping to improve stability
  • Implemented over numerous rivers at various spatial resolutions

\[\frac{\Delta h}{\Delta t} = \frac{\Delta Q}{\Delta x \Delta y}\] \[\underbrace{\frac{\partial Q}{\partial t}}_{acceleration} + \underbrace{\frac{\partial}{\partial x} \frac{Q^{2}}{A}}_{advection} + \underbrace{\frac{g A \partial (h +z)}{\partial x}}_{water~slope} + \underbrace{\frac{g n^{2} Q^{2}}{R^{4/3}A}}_{friction~slope} = 0\]

Sub-grid channel formulation

lisflood_subgrid.png

Model configuration

  • Inputs required
    • Floodplain topography
    • River channel widths and bank heights
    • Model parameters
    • Boundary conditions
  • Spatial resolution of 1 km
  • Model initialized at 80% of bankfull depth
  • No calibration performed, default parameters used
    • Rectangular channel
    • Roughness coefficient = 0.035

Pre-processing steps

  1. Resample DEM to 1-km resolution
  2. Generate the river network and chainage
  3. Estimate and smooth river bank heights
  4. Identify upstream and lateral boundary locations
  5. Generate boundary inflows
  6. Derive river channel cross-sections

River network and DEM

arkansas_dem_river.png

River bank heights, widths and depths

  • Channel widths and depths are prescribed from HydroSHEDS database
  • Bank heights needed for sub-grid model
  • Assumption that HydroSHEDS DEM is bankfull elevation
  • Locally weighted smoothing applied to avoid numerical instabilities

lowess.png

Boundary inflows

jan_1_2014_vic_hourly_0-100cm_soil_moisture.gif NLDAS-2 surface runoff & baseflow

VIC_routing_model_schematic.png VIC routing model

arkansas_bdy.png Boundary inflows

Simple Unit Hydrograph routing

arkansas_vic.png

Simulation period: 1/1/2000 - 12/31/2010 

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LISFLOOD-FP version 6.1.2 (double)
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Starting time steps: acceleration mode

SGC mode
Using sub-grid channels and acceleration formulation

OMP thread count: 16

  Total computation time: 1847.93 mins

Maximum water depth

arkansas_wdmax.png

Comparison with streamflow measurements

arkansas_q.png

Next steps

  • Model pre-processing has been automated
  • Extend simulation to entire Mississipi basin
  • Use 95th percentile widths and depths
  • Evaluate different channel shapes (e.g. parabolic)
  • Data assimilation algorithms for generating Level-4 products being developed