The FEWS Flood Risk Monitoring Model From Rain to Rivers

1
The FEWS Flood Risk Monitoring ModelFrom Rain to
Rivers

• Tanya Hoogerwerf
• Thursday, February 22, 2001

2
FEWS Model

• Provides a continuous simulation of stream flow,
  on a daily time step, for nearly 3,000 basins on
  the African continent.
• Rainfall/runoff simulation model containing
• a soil water accounting module that produces
  surface and sub-surface runoff for each sub-basin
• an upland headwater basins routing module
• and a major river routing module.

3
Runoff Producing Mechanisms

• Surface runoff due to precipitation excess
  (including direct runoff from impermeable areas
  of the basin)
• Rapid Subsurface Flow (interflow), and
• Base Flow

4
Soil Water Accounting Module (SAC-SMA) Revisited
FEWS Active Zone (2 layers) Groundwater Zone
(1 layer)
Active Layer
Baseflow
5
Runoff Calculations

• The HYDRO1K data provide basin boundaries and
  stream networks that form the spatial framework
  of the model.
• The FAO soil map provides characterization of the
  hydraulic properties of the earth's surface that
  are required to compute the water balance within
  a basin.
• The NOAA RFE provide the estimates of gross
  precipitation input to each basin.

6
Total Channel Inflow (SAC-SMA)

• uT Channel Inflow from SWC Surface Runoff
  Base Flow Runoff
• Surface Runoff f(Precipitation, Soil Water
  Content, SR Gen.)
• Base Flow Runoff f(BF Recession Rate, SWC, BF
  Lost to Aquifers)
• Water Balance Relationship for Each Reach
• dSidt Ui-1 piuT Ui
• SWater Volume
• Pi Fraction of Total Water Inflow Corresponding
  to Reach i
• Ui Reach i
• Ui-1 Upstream Inflow from Reach i-1

7
Time of Concentration Grid

• Slope, flow direction, and flow accumulation
  grids of the HYDRO1K
• Manning equation for flow in an open channel
• Units 1/10 day

8
Rainfall

• NOAA has produced RFE images (Herman et al.,
  1997) on a dekadal (10-day) time step
• Basin Excess Rainfall Maps (BERM) Produced

9
Output

• Mozambique Flood Information Stream Flow Model
  Flood Risk Map Page (select Pfafstetter Basin)

10
References

• USGS/EROS Data Center http//edcsnw3.cr.usgs.gov/i
  p/gflood/
• Riverside Technology
• Real-Time Prediction for Flood Warning and
  Management- Georgakakos 1995

• Coupled Rainfall-Flow Forecasting Models-
  Georgakakos