Flood Forecasting and Emergency Response
Dr. David R. Maidment
Center for Research in Water Resources University of Texas at Austin
TxDOT Transportation Short Course, Texas A&M University, 12 October 2016
Acknowledgements: City of Austin, National Weather Service, Texas Division of Emergency Management, National Science Foundation, Colleagues and students at UT Austin An Opportunity
New National Water Center established on the Tuscaloosa campus of University of Alabama by the National Weather Service and federal agency partners Has a mission to assess hydrology in a new way at the continental scale for the United States 3DO11/3/2016 NOT DISTRIBUTE
Inaugural Meeting – May, 2014 National Flood Interoperability Experiment
• Partnership between NWS and the academic community
• Included Summer Institutes for graduate students at National Water Center in 2015 and 2016 Stampede
1.2 million gallon cooling tank
500,000 processors operating in parallel
5 NHDPlus Version 2.1
Foundation for a Geospatial Hydrologic Framework for the United States
NHDPlus
2.7 million reach catchments in US average area 3 km2 reach length 2 km Uniquely labelled
National Elevation Dataset Watershed Boundary Dataset
National Hydrography Dataset National Land Cover Dataset
Forecasts
Now
Analysis Best estimate of current conditions
Short Range Hourly for 15 hours ahead (15 time steps)
Medium Range 3 Hourly for 10 days ahead (80 time steps)
Long Range Daily for 30 days ahead (30 time steps) Ensemble of 4 forecasts each 6 hours (24 forecasts total) Operational with publicly accessible forecasts as of 16 August 2016
ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/nwm/prod/ FEMA National Flood Hazard Layer in Texas (~ 120 counties)
Large areas of Texas lack flood information
Blanco County
Hidalgo County, Population 774,000 Cameron County Population 420,000 Flow Continuum Model – a national stream network, atmosphere to oceans, coast to coast
Blanco River at Wimberley Current: 6600 basins and 3600 forecast points Two basins and one forecast point
Basin ~ 400 Sq Mile
becomes NFIE: 2.7 million stream reaches and catchments
Reach Catchment ~ 1 Sq Mile
130 Catchments and Flowlines uniquely labelled A national flow network Flow Continuum Model – a national stream network, atmosphere to oceans, coast to coast
Blanco River at Wimberley Current: 6600 basins and 3600 forecast points Two basins and one forecast point
Watershed Hydrology – basinsBasin ~ 400 and Sq Mile outlet points
becomes NFIE: 2.7 million stream reaches and catchments
Continental Hydrology – network flow continuum
Reach Catchment ~ 1 Sq Mile
130 Catchments and Flowlines uniquely labelled A national flow network Experiment for 2016: Combine hydrography and elevation to define river channel geometry and flood inundation extent for 5 million km of stream reaches over continental US
National Hydrography Dataset National Elevation Dataset
Use the CyberGIS computing facility at the University of Illinois at Urbana-Champaign NWS Flood Inundation Maps for the US (130 in total) Real-Time Flood Inundation Mapping
Black Warrior River at Oliver Lock and Dam
Flooding Real-Time Flood Inundation Mapping
Black Warrior River at Oliver Lock and Dam
Flooding
Minor Real-Time Flood Inundation Mapping
Black Warrior River at Oliver Lock and Dam
Flooding
Moderate
Minor Real-Time Flood Inundation Mapping
Black Warrior River at Oliver Lock and Dam
Flooding
Major
Moderate
Minor Method for Determining Flood Risk: Height Above Nearest Drainage (HAND)
Flooding occurs when Water Depth is greater than HAND
Height Above Flood Depth Nearest Drainage (HAND) Normal Depth
Stream Bed Flood Inundation Mapping – NHDPlus-HAND Method
Water surface elevation y h = z + y NHDPlus h z Geodetic datum
Catchments and Flowlines
Height Above Nearest Inundation map Drainage (HAND) Height above (relative elevation of land drainage < 15 ft) Digital Elevation Model surface cell above cell in NHDPlus stream to which it flows) Continental-Scale Flood Inundation Mapping
Catchments and Flowlines
Height Above Nearest Drainage (HAND) (relative elevation of land surface cell above cell in Digital Elevation Model stream to which it flows) Height Above Nearest Drainage for the Continental United States
A continuous foundation for flood inundation mapping Reach Hydraulic Parameters
Comid y A R P T V Ab As
5781175 3
5781175 4
As Surface Area
Wetted Bed Area Ab L V Volume T 푉 퐴 = Cross Section Area A 퐿 Depth y 퐴 P P= 푏 Wetted Perimeter 퐿 퐴 T= 푠 Top Width 퐿 퐴 R= Hydraulic Radius 푃 Reach Catchment 5781289
Eanes Creek, Rollingwood, Texas
Drainage area = 3.13 mi2
Reach Length = 4.3 miles Discharge Computation
Hydraulic Radius, R Flood Discharge, Q (cfs) 1.49 푄 = 퐴푅2/3푆1/2 푛 표
Flood Depth, h (ft)
Cross section Area, A n = 0.035 Manning roughness of channel
So = 0.0163 Bed slope Rating Curve for Eanes Creek
Rating Curve for Eanes Creek, ComID = 5781289 12
10
8 Flood Depth, y (ft) 6 1.49 푄 = 퐴푅2/3푆1/2 푛 표
Stage Height (ft) Height Stage 4 Forecast Discharge, Q, from National Water Model 2
0 0 5000 10000 15000 20000 25000 Discharge (cfs) Continental-Scale Flood Inundation Mapping
1. Forecast discharge with National Water Model 1 2. Convert discharge to depth using rating curve 3. Convert depth to inundation using HAND
2
3 HAND-based Mapping for Tuscaloosa County
Normal Conditions HAND-based Mapping for Tuscaloosa County
Normal Conditions
Start to Rise HAND-based Mapping for Tuscaloosa County
Normal Conditions
Start to Rise
Main Flooding HAND-based Mapping for Tuscaloosa County
Normal Conditions
Start to Rise
Main Flooding
Start to Recede HAND-based Mapping for Tuscaloosa County
Normal Conditions
Start to Rise
Main Flooding
Start to Recede
Returning to Normal Area of Concern in Moundville
Red dots are Address Points People trapped by floodwaters
Remarkable that a continental-scale flood inundation map can correctly identify this issue Flood Emergency Response Exercise for Tuscaloosa County Texas Division of Emergency Management (TDEM) Flood Response Project Stakeholders
County Partners State Partners • Travis County Commissioners • Texas Division of Emergency • Capital Area Fire Chief Management (TDEM) • Association (CAFCA) • Texas Natural Resource • Travis County Emergency Management Information Systems (TNRIS) • Travis County Sheriff's Office • Texas Water Development • Williamson County Emergency Management Board (TWDB) • Williamson County Sheriff’s Office • Texas Commission on • Williamson County Fire Chiefs Environmental Quality (TCEQ) • Upper Brushy Creek Water Control District • Texas Department of • San Marcos Emergency Management Transportation (TxDOT) • Hays County Emergency Management • Texas Floodplain Managers
City Partners Federal Partners • City of Austin • National Weather Service (NWS) • Austin Fire Department • National Oceanic Atmospheric • Austin Flood Early Warning Administration (NOAA) System (FEWS) • Federal Emergency Management • Austin Homeland Security Agency (FEMA) Emergency Management (HSEM) • US Geological Survey (USGS) • Houston Office of Emergency • US Army Corps of Engineers (USACE) Management Rating Curves computed for 98,000 reaches on 190,000 miles of rivers and streams in Texas
Real-time flood inundation mapping is possible for all of Texas Connect the stream network and road network?
Forecast flood impact on roads and bridges statewide Radar Measurement Technologies
Measures surface velocity ($12,000)
Measures water level ($5000)
Densified forecasting requires densified measurement Stream Measurement in Texas
550 USGS Gages 54,000 TxDOT Bridges
Gold Standard Potential Sensor Platforms Streamflow Observation and Modeling in Texas
1: USGS Stream gage sites (~ 550) (Level and Flow) Gold standard
Water Level and Surface Velocity
Water Level
:185 National Water Model Computation (102,000 in Texas) Iowa Flood Center STREAM SENSORS Stream Measurement in Iowa 237 USGS Stream Gages Stream Measurement in Iowa 237 USGS Stream Gages
224 Iowa Flood Center Stream Sensors
2 support staff Stream Measurement in Texas
54,000 TxDOT Bridges 550 USGS Gages Stream Measurement in Texas
54,000 TxDOT Bridges 550 USGS Gages
Instrument 1 bridge in 100 – 550 sensors
Instrument 2 bridges in 100 – 1100 sensors
Double or triple the number of measured stream locations Conclusions and Next Steps…
• Water is now forecast like weather – 98,000 reaches of 190,000 miles of rivers and streams in Texas This is transformative for our state!
• Could TxDOT adopt a policy of putting a water level sensor on a bridge as a standard piece of equipment?
• Can flood impact on roads and bridges be forecast state-wide?
• Can we collaborate with TxDOT to improve Texas flood resilience?