Improving Flash Flood Prediction in Application of a Distributed Model in

Areas of Complex Terrain

Michael Schaffner, NOAA/NWSPatrick Broxton, UA

Peter Troch, UADavid Goodrich, USDA-ARS

Hoshin Gupta, UACarl Unkrich, USDA-ARS

Thorsten Wagener, Penn State

UCAR Award No.: S09-75794

Flash Flood Prediction in Small Fast Responding Basins

• Generally involves mapping radar rainfall to small basins using the Flash Flood Monitoring and Prediction Program (FFMP).

• Running a “site specific” lumped model (utilizing hourly rainfall input and hourly time steps) for gaged basins. API model and SAC-SMA model. KINEROS model at Weather Forecast Office (WFO) Binghamton.

For heavy rains, KINEROS is used to predict flow hydrograph

In model scheme, will run at high spatial and temporal resolution during events

KINEROS Overview 3

- Event based, distributed

- High temporal and spatial resolution

- Kinematic wave equations to route channel flow

- Consists of a series of overland flow planes and channel elements

- Dynamic Infiltration

KINEROS Current Usage 4

- Used operationally at NWS Binghamton on 9 basins.

- Being tested nationally under the NWS HOSIP process at a total of 4 WFOs in Eastern, Central, and Western Region:

-Pittsburgh, PA-La Crosse, WI-Kansas City, MO-Portland, OR

Motivation: To Improve Upon Existing Flash Flood Forecasting Methodologies of the KINEROS Model

• Initial Soil Moisture Conditions

5

- What is the catchment’s ability to absorb incoming precipitation during a given storm event?

• Precipitation Uncertainty and Precipitation Type- What is the “true” precipitation input that results in a flood?

• Catchment Response in Humid Regions- How does runoff get generated during storm events?

- Model Improvement: Because the flash flood model (KINEROS) in this study is an event-based model, we use a continuous model (SM-hsB) to keep track of the hydrologic state with which to initialize KINEROS

- Model Improvement: In addition to gridded and point precipitation measurements, we add support for snow so that flood events involving snowmelt can be modeled

- Model Improvement: Adding a subsurface flow component will improve KINEROS’s ability to reproduce observed hydrographs in humid catchments

- Modules to handle:

Water and energy balance at land surface while incorporating snow

Root zone water balance and lateral subsurface transport of soil water

Keep track of the hydrologic state between KINEROS runs

In model scheme, will run at lower spatial and temporal resolution between events

Transmission Zone

Root Zone

hsB Aquifer

Deep Aquifer

Infiltration

ET

SM-hsB Overview 6

- Continuous, semi-distributed Model

- Five Watersheds in New York’s Catskill Mountains:- Humid catchments that are focus of current efforts

1) W Branch Delaware River at Walton, NY (332 sq mi)

2) W Branch Delaware River near Delhi, NY (134 sq mi)

3) East Brook near Walton, NY (25 sq mi)

4) Platte Kill near Dunraven, NY (35 sq mi)

5) Town Brook near Hobart, NY (14 sq mi)

Study Sites – New York Watersheds 7

- Three watersheds in Arizona:- Semi-Arid catchments to compliment humid catchments

1) Sabino Canyon at Tucson, AZ (332 sq mi)

2) Rincon Creek near Tucson, AZ (134 sq mi)

3) Walnut Gulch near Tombstone, AZ (25 sq mi)

Study Sites – Arizona Watersheds 8

Study Sites – Comparison 9

Average Temperatures: -20 – 20°C

- New York Watersheds:

- Arizona Watersheds:

Average Annual Precipitation: ~1000-1300 mm

Average Temperatures: -5 – 40 °CAverage Annual Precipitation: ~300-800 mm

Few orographic effects, less than 1/3 of precip falls as snow, floods can occur at any time of year

Strong orographic effects, flash flood events are typically caused by summer rains

Annually, ~70% of precipitation is translated into streamflow

Annually, ~15% of precipitation is translated into streamflow

Data Sources 10

- Calibration Data

- North American Land Data Assimilation System (NLDAS)Historical gridded reanalysis of hydrometeorologic variables

- Historical Gauge Data

- Snow Data Assimilation System (SNODAS)

Historical Snow Information used to calibrate snow model

- Historical distributed hydrometerologic data

MPE

SNODAS

Reanalysis of historical temperature, pressure, humidity, wind speed, downward shortwave radiation, downward longwave radiation, precipitation

Can be used to validate gridded products

- Multisensor Precipitation Estimator (MPE)Gridded Precipitation Estimates based on radar and gauges

Data Sources 11

- Real Time Data

- National Digital Forecast Database (NDFD)

- Multisensor Precipitation Estimator (MPE)

NWS Gridded forecasts

Gridded Precipitation Estimates based on radar and gauges (used as input to hsB modeling)

- DHR, Q2, HPE/HPN

High resolution precipitation estimates and precipitation nowcasts (used as input to KINEROS modeling)

- Distributed data that is disseminated in near-real time

MPE

NDFD

Q2

Current and future projections of temperature, humidity, wind, and cloud cover (to be used with hsB modeling)

Future projections of rain and snow amounts

KINEROS Calibration 12

- Typical hydrographs for Platte Kill Watershed in the New York (absence of subsurface flow)

- Designed for semiarid environments where overland flow dominates.

-Calibration of global multipliers of saturated hydrologic conductivity and channel length.

-Events are calibrated using a Z-R Relationship that matches ground truth

- This project seeks to extend it to work well in humid catchments

SM-hsB Calibration 13

- Subsurface flow component calibration procedure is fully automatic and based on matching the baseflow characteristics of the stream hydrograph

- Energy Balance/snow component calibrated based on visual inspection using all available data

- Each Component must be calibrated separatelyMarch 1, 2010February 27,2010January 23,2010

200 mm

0

100 mm

Coupling KINEROS and SM-hsB to run in Real Time 14

- This part of the system will run with a coarser temporal time step (~1 hour) and with fewer spatial discritizations than the high resolution portion

- Ongoing work includes:

- Keep track of catchment wetness so KINEROS can be initialized with the correct initial conditions

- Also provide simple flood risk assessment taking into account potential snow melt

- Implement continuous SM-hsB model in Real-Time to keep track of hydrologic state during interstorm periods

- Keep track of snowmelt and initial snowmelt

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- Initialize KINEROS with correct initial conditions during flooding, combine subsurface flow dynamics so it better matches observed flow hydrographs

- Ongoing work includes:

- Subsurface dynamics of SM-hsB model will have same temporal and spatial frequency as KINEROS using infiltrated water from KINEROS planes

- Distributed and run at a very small temporal timestep (5 min)

- Initial states, projected snowmelt called from the continuous model component

Coupling KINEROS and SM-hsB to run in Real Time

hsB Hillslopes KINEROS Hillslopes

16Summary

- Use SM-hsB to keep track of hydrologic state between events, initialize KINEROS using those states

- Add support for snow; forecast flooding that involves rapid snowmelt and rain-on-snow

- Improve KINEROS’s ability to reproduce hydrographs in humid catchments by adding a subsurface flow module

• Coupling of models has three primary objectives:

• Models have been calibrated and tested in humid New York basins as well as semi-arid Arizona basins

• Final model system will consist of two parts:- Lower resolution continuous model to keep track of hydrologic state and to do simple flood risk assessment-Higher resolution event-based model to simulate the flood hydrograph given current and forecast rainfall

17Questions?

Contact info:Michael SchaffnerSenior Service HydrologistMike.Schaffner@noaa.gov607-770-9531, ex. 234

Reference: S. Yatheendradas, T. Wagener, H. Gupta, C. Unkrich, M. Schaffner, D. Goodrich, A distributed, real-time semiarid flash-flood model utilizing radar data, Regional Hydrologic Impacts of Climate Change, IAHS Publ. 296, 2005.