Flash Flood Prediction

7/27/2019 Flash Flood Prediction

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Flash Flood Prediction

Working GroupQ2 Workshop

June 28-30, 2005


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Provide river and flood forecasts andwarnings for the protection of lives andproperty.

Provide basic hydrologic forecastinformation for the nations environmentaland economic well being.

Mission of NWS

Hydrologic Services Program


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Current Flash Flood Services

Primary WFO Products and Information

Flash Flood Watch

Flash Flood Warning

NATIONAL WEATHER SERVICE INSTRUCTION 10-922

WEATHER FORECAST OFFICE HYDROLOGIC PRODUCTS SPECIFICATION

http://www.nws.noaa.gov/directives/010/010.htm

BULLETIN - IMMEDIATE BROADCAST REQUESTED

FLOOD WATCHNATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA

930 AM PST WED FEB 18 2004

...A FLASH FLOOD WATCH CONTINUES UNTIL 1100 PM FOR THE BURN AREAS OF

VENTURA AND LOS ANGELES COUNTIES...

A FLASH FLOOD WATCH MEANS THAT FLASH FLOODING IS POSSIBLE...

BUT NOT IMMINENT...IN THE WATCH AREA. PEOPLE IN THESE AREAS

SHOULD STAY ABREAST OF THE LATEST DEVELOPMENTS AND BE PREPARED

TO TAKE IMMEDIATE ACTION IF A WARNING IS ISSUED OR FLOODING

IS ENCOUNTERED.


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Current Flash Flood Services

Product Dissemination Internet (http://weather.gov/)

NOAA Weather Radio

Emergency Managers Weather InformationNetwork

NOAA Weather Wire Service

Family of Services

NOAAPORT

EAS


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Verification

Flash Flood Warning verification statistics

are based on product issuance information

and confirmation of actual flash floods by

the local WFOs. Flash Flood Warning Lead Time

Flash Flood Warning Accuracy

FY03Actual

FY04Actual

FY05

Actual

(OctMar)

FY05Goal

FY2012

Goal

(FY08 PBA)

Lead Time

(minutes)41 47 64 48* 51

Accuracy

(%) 89 89 89 89 91


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Impact of Technology, Training, Expanding Outreach and

Dissemination on Flash Flood Services

National Average Annual Flash Flood Warning Lead Time

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LeadTim

einMinute

NEXRAD

Implementation

Where will the next improvement come from?

FFMP

Implementation


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Data and Decision Assistance Tools

Forecasters integrate observed and forecastinformation to assess the threat of flash

flooding

Data sources include radar data and in-situ

precipitation gages and FFG (e.g., ASOS andALERT)

Decision assistance tools facilitate analysis of

large and diverse data sets to identify

conditions conducive to flash flooding


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Current Operational Practices for

Predicting Flash Flood

FFMP

The Flash Flood Monitoring and Prediction (FFMP)

Application is a new NWS radar-based Advanced

Hydrologic Prediction Service (AHPS) decisionassistance application

Site Specific

DamCREST

Traditional Methods


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FFMPAvailable Data and Algorithms


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Outstanding Science and Research to

Operations Issues

Radar data availability is limited especially in the Western UnitedStates

WFOs served by more than one radar must run an instance ofFFMP for each radar

Limitations of radar Uses raw radar data precipitation estimates no bias adjusting

Radar bins increase in size and altitude with distance from the radar

Brightband contamination

Hail contamination

Inaccurate Z/R relationships

Limitations of FFG

FFG is developed from hydrologic models calibrated for riverforecasting of larger basins. The calibrations are not necessarilyscalable for the basins associated with flash floods.

Discrepancies across RFC boundaries

Not appropriate for regions where the dominant flash flood factorsare rainfall intensity and terrain


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Emerging Scientific Solutions for

Predicting Flash Flood

Improved radar estimates of precipitation Probabilistic QPE from Radar

Dual polarization radar precipitation estimates

Precipitation estimation from TDWR Improved Multi-sensor Precipitation estimates

Improved Short Range QPF

FFMP improvements

Flash Flood Potential Index Statistical Distributed Modeling

Distributed Modeling


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Emerging Scientific SolutionsFFMP Improvements

Current research to operation efforts

Generate regionally-mosaicked, multi-

sensor precipitation estimates every volume

scan displayed on a 1 km grid for the timescales used in FFMP (0.5 hour, 1 hour, 2

hour and 3 hour)

Ingest gridded precipitation estimates(NMQ, MPE, Q2, QPF) into FFMP

Toggle between multiple QPE inputs


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Emerging Scientific SolutionsFFMP Improvements

Enhanced QPE/QPF Capabilities (NWS OperationalRequirements Document - Flash Flood Monitoring and PredictionFall 2003)

If scientific investigation shows that the increased spatial resolution isbeneficial to precipitation estimates, then increase the spatialresolution of the multi-sensor precipitation estimates to 0.5 km by 0.5

km. Increase frequency of integration of satellite QPE into multi-sensor

precipitation estimates from every 60 minutes to every 15 minutes

Generate DHR-based rainfall products with a resolution of 0.5 by0.25 km (ORDA FY08)

Provide capability to display and monitor QPF

Enhance the rain gauge network data flow from all sources anddeliver to AWIPS for use in multi-sensor precipitation estimates andFFMP at 5 minute resolution.

Other requirements identified in the ORD include GISimprovements, improvements in FFMP Display methods, andimprovements in FFG estimates


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obtain raster (gridded) datasets representing the features of interest

Utilize GIS tools/methods to develop a single index that represents the a

potential for flash flooding (on a relative scale)

Emerging Scientific SolutionsFlash Flood Potential Index


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Gridded

Relative

Flash Flood Potential



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STATSGO Dominant Soil TextureMLRC Land Use / Land Cover

NOAA AVHRR Forest Density Grid

USGS DEM (derived % slope Grid Terrain)

Fire Burn Areas / Severity coverage

Relative Flash Flood Potential

An indication of rapid hydrologic response

Low High

Summarize Grids to Geographic Layer (Basin)

FFMP Basins



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Currently researching methods to add a

soil moisture layer to FFPI to support

national implementation.

Will need to integrate gridded 1-hour multi-

sensor precipitation estimates to estimate

soil moisture.


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Peak Flow Climatology for Flint Creek at Springtown, AR (10 peaks

per year were extracted from WY 1997 - 2002)

1

10

100

0.01 0.1 1

Prob of exceeding bankfull

Flow

(cms)

Observed

Simulated

(2)

(1)0.82 0.63

Regional flood threshold

estimate

(3) Forecasted peak flow

Methodology1. Using observed data

for a region, derive a

probability distribution

describing the chance of

exceeding a flood

threshold given a

computed flow frequency

2. Derive a simulated

climatology for each

model grid cell

Shaded area is probability ofexceeding bankfull flow.

3. Given a forecasted

flow, derive the probability

of exceeding simulated

climatology for each

model grid cell

Emerging Scientific SolutionsStatistical Distributed Model


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Emerging Scientific SolutionsStatistical Distributed Model

Precipitation Estimation requirements

Initial Proof of Concept with Hourly Stage III

products on an HRAP grid.

Model framework can be used to test

precipitation estimates at higher spatial and

temporal resolutions

Plan to expand approach to ingest 1-hourforecast precipitation grids.


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Arkansas R.

Red R.

Blue R.

Emerging Scientific SolutionsDistributed Modeling

Distributed Model Intercomparison Project

E i S i tifi S l ti


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Hydrologic Response at Different Points in the

Blue River Basin

Hydrograph at Location A

Hydrograph at Location B

Hydrographs at Basin Outlet

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Flow(

CMS)

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Flow(

CMS)

B

A Distributed

Lumped

Observed

Flow

(CMS)


Emer

ging Scientific Solutions


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Application of HL Distributed Model



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Precipitation Estimation requirements

Hourly Stage III products on an HRAP grid.


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Precipitation Requirements for

Flash Flood Prediction Improved quality of precipitation estimates

Accurate highresolution seamless multi-sensor griddedprecipitation estimates

Timely estimates every five minutes as close to real-time(minimize processing, latency, without degradingquality)

Ingest short-term (0-1 hour) high quality seamless QPF

Carry forward human quality control knowledgeinteraction to real-time QPE estimates

Improve gauge quality and network Gap filling mechanisms

Satellite estimates

Hourly updates for soil moisture components


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Other Priorities for

Flash Flood Prediction

Improved FFG

Societal Impacts and Public Perception

Verification

Ground Truth

Flash Flood Climatology

Training

GIS Solutions - Fire scars Uncertainty

Visualization

Flash Flood Prediction

Documents

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