Hydrology in the National Weather Service

Mark FuchsService Hydrologist

National Weather ServiceSt. Louis, MO

Presentation to local Media PartnersNovember 16, 2013

• Define flooding and hydrology• Describe factors that contribute to flooding and define flooding categories• Describe the CHPS and the hydrologic forecast process at the RFCs• Provide an overview of the Advanced Hydrological Prediction Service (AHPS) resources and 90-day streamflow outlook tools• Provide additional NWS resource locations

Objectives

Growing Demand for Water Information

• Flash Flood – a rapid and extreme flow of high water into a normally dry area, or a rapid water level rise in a stream or creek above a predetermined flood level, beginning within six hours of the causative event (e.g., intense rainfall, dam failure, ice jam).

• Flood – high flow, overflow, or inundation by water which causes or threatens damage.

Flood vs. Flash Flood

• Pre-season water levels• Received precipitation/snowfall• Air/ground temperature• Soil moisture• Ice Jams• Snowpack/snow melt

Factors Contributing to a Flood

• Action Stage: Water is near or over the top of its banks in spots, but no structures are flooded; any flooding is typically limited to parkland and marshland.

• Minor Flood Stage: Few buildings are expected to be inundated, roads, parklands and yards may be covered with water and water may go under buildings on stilts or higher elevations.

• Moderate Flood Stage: Inundation of buildings, roads closed and/or cut off. Some evacuations may be necessary.

• Major Flood Stage: Significant to catastrophic, life-threatening flooding is expected. Extensive flooding with some low-lying areas completely inundated. Structures may be completely submerged. Large-scale evacuations may be necessary.

Flood Categories

NWS USACE USGS

• NWS – Forecasts• USACE – Engineering and Reservoirs• USGS – River observations and measurements

USGS and USACE river gauges

USACE water control

NWS OperationsAverage Person Only Sees Tip of Iceberg

Private Weather Companies

InternetRadioTV

NWR

122 Weather Forecast Offices

9 National Centers for

Environmental Prediction

13 RiverForecastCenters

Radar Network

SatellitesWeather Balloons

Ground-LevelObservations

Data Buoys

Climate andSeasonalOutlooks

VolunteerNetwork

ModelSimulations

Aviation & Ocean Forecasts

Severe Thunderstormand Tornado Prediction

Space WeatherForecasts

HurricaneForecasts

Government

StreamGauge

Network

River Forecasts

90-day outlooks

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NWS OperationsPresence at National, Regional and Local Levels

NWS River Forecasts

NWS River Forecast Centers

www.water.weather.gov/ahps/rfc/rfc.php

Three River Forecast Centers serve the St. Louis Service Area

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MBRFC

NCRFC

LMRFC

FCFEWS

National Weather Service Northeast River Forecast Center 15

CHPS: Community Hydrologic Prediction System

FEWS Models

NWS Models

HEC Models

Other Models

CHPS

CHPS NERFC – Alternative data views

CHPS: Providing the forecaster an interface to data

• Intuitive graphical interfaces• Lots of map support• Highly configurable views

CHPS NCRFC – flood status in several catchments

CHPS: Data visualization and editing – Graphical data

• Powerful graphical tools for viewing time series data

• Point time series Longitudinal profiles (animated)

• Editing capabilities – copy to-from e.g. Excel

Historical event: River Rouge, Detroit

Longitudinal Display

CHPS: Using and displaying probabilistic data

• Import ensemble data (e.g. ECMWF, GFS, NAM)• Run models for ensemble members• Results

– Statistical Summary– Verification

The CHPS database model is inherently ensemble-aware

Model #2 for 31-05-2007 00:00 UTC

Model #1 for 31-05-2007 00:00 UTC

Hydrologic Forecast Process

Modeling how much rain gets into the river (Rainfall to Runoff)

Modeling snowmelt runoff (Snow model) Modeling how fast water gets to the river

gage (Unit Hydrograph) Modeling how fast upstream water arrives

at the gage (Routing) Translating water volume into water height

(Rating)

Soil Moisture Conditions

Accumulated snow and ice pack

Observed Precipitation

Forecast Precipitation

Rainfall to Runoff Modeling

6 12 18 24 30 36 42 48 54 60 66 72 78 84 90 96 102 108 114 120 126 132 138 144 150 156

0

2000

4000

6000

8000

10000

12000

14000

Series1

Time (hours)

Unit HydrographMeramec River near Steelville, Missouri

Flow

(cfs

)

Routing

Time

Gage

Heig

ht

River Forecasts – How are they created?River Forecasts – How are they created?

Observed PrecipitationObserved

PrecipitationFuture

PrecipitationFuture

Precipitation

Soil ModelRainfall to Runoff

Soil ModelRainfall to Runoff

Local Basin

Rating CurveFlow to StageRating CurveFlow to Stage

Unit HydrographRunoff to Flow

Unit HydrographRunoff to Flow

Upstream FlowUpstream FlowUpstream River Gage

Basin Local FlowBasin Local Flow Total Flow(cfs)

Total Flow(cfs)

ForecasterModificationForecaster

ModificationForecastTo PublicForecastTo Public

Forecast River Gage

Forecast Considerations

Ground State (How dry is it?) Past Model Performances Rainfall (Gage-based or Radar-based?) Rainfall Variability

• Space• Time

Rainfall Variability

Rainfall Variability

Rainfall Variability

Rainfall Variability

Rainfall Variability

RFC Products and Services

WFO Products and Services

• These graphical products are useful planning tools.

• Enable users to make more informed decision about policies and actions to mitigate the dangers posed by floods and droughts.

• New feature demo

AHPS

River Forecasts

ImpactsWhat constitutes impacts?– Flooded cropland and parks– Flooded roadways– Damaged storage buildings and garages– Businesses and residences– Levee breaches vs. overtopping– Navigational issues– Water intake problems

Defined as any water level disrupting human activity.

Impacts

Low Flow and Impacts

Experimental Long-Range River Flood Risk

Probability Outlooks

Probability Outlooks

Spring Outlooks

December 2013 – February 2014

December 2013 – February 2014

Resources

• www.water.weather.gov• www.weather.gov• www.cpc.ncep.noaa.gov• www.wpc.ncep.noaa.gov• www.nohrsc.nws.gov

Questions