Difference between revisions of "Flood Forecasting"

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== Flood Forecasting ==
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==Flood Forecasting==
  
 
Our current plans for flood forecasting involve three phases:
 
Our current plans for flood forecasting involve three phases:
  
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# Short-term prediction
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#Short-term trend extrapolation
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# Crest prediction
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#Crest prediction
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# Flood forecasting
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#Short-term forecasting
  
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=== Short-term Prediction ===
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===Short-term Prediction===
  
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By "short-term prediction", we mean extrapolating from current water levels in order
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By "short-term prediction", we mean extrapolating from current water levels in order to predict when near-term critical events like road-crossings will happen.
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to predict when near-term critical events like road-crossings will happen.
 
  
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=== Crest Prediction ===
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=====Linear Trend Extrapolation=====
  
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We want to be able to predict crest timing at a particular gage or area based on the
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*On the gage details page
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timing of crests at upstream gages.
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**Create extrapolated readings every 15 minutes from the last reading until last reading + 6 hrs.
 +
**Show extrapolated readings on chart with a different color.
 +
**If extrapolated readings cross a road (rising or falling) display a notice:
 +
***"Based on current trend, the flood water will be [higher / lower] than the road after HH:MM pm/am"
  
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=== Flood Forecasting ===
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*
  
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Long-term, we want to build a model using all of the possible inputs that might
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===Crest Prediction===
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have an effect on water level.  Examples:
 
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* Weather forecasts
 
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** Rainfall
 
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** Temperature
 
  
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Using this model, we want to be able to try to predict water levels well in advance of flood events.
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We want to be able to predict crest timing at a particular gage or area based on the timing of crests at upstream gages.
 +
 
 +
*For each gage build a model for each upstream gage that predicts the timing of the gage's crest based on the timing and height of the upstream gage
 +
**For example, if gage C has two upstream gages, A and B. Build two models. One that predicts the timing of the crest of C based on A and one based on B.
 +
*Only consider gages from USGS at the falls to USGS at Duvall
 +
*Formalize the definition of a crest
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**Something like: crest is confirmed after three down readings with no up readings.
 +
**How do we handle a turbulent gage?
 +
**How do we calculate the time of the crest? First highest point?
 +
*Phase I: Height independent. Calculate median time based on past data.
 +
*Phase II: Try to model hight. Maybe start with simple linear fit.
 +
*Gage Details page:
 +
**Show prediction based on nearest upstream gage that has crested
 +
**Show confidence interval with prediction
 +
**Example:
 +
***Estimated crest at Gage C based on observed crest at Gage A: 5:10 pm (+/- 90 minutes)
 +
 
 +
===Flood Forecasting===
 +
 
 +
===== Model Based Short-term Prediction =====
 +
Predict the next 4-12 hours at each gage. Most short term (4-12 hrs) flooding impacts in the lower valley will be the result of rain that has already fallen.  
 +
 
 +
We should consider using the following inputs to build a model:
 +
 
 +
*Gage trend
 +
*Upstream readings and trends
 +
*Upstream major tributary readings and trends (Tolt, Raging, 3 forks)
 +
*Meteorological readings from various stations in the watershed:
 +
**Temperature
 +
**Snowpack
 +
**Rainfall
 +
 
 +
Predict the following for each gage:
 +
 
 +
*Road crossing time
 +
*Yellow / Red status change time
 +
*Crest time
 +
*Crest height

Latest revision as of 16:07, 18 May 2020

Flood Forecasting

Our current plans for flood forecasting involve three phases:

  1. Short-term trend extrapolation
  2. Crest prediction
  3. Short-term forecasting

Short-term Prediction

By "short-term prediction", we mean extrapolating from current water levels in order to predict when near-term critical events like road-crossings will happen.

Linear Trend Extrapolation
  • On the gage details page
    • Create extrapolated readings every 15 minutes from the last reading until last reading + 6 hrs.
    • Show extrapolated readings on chart with a different color.
    • If extrapolated readings cross a road (rising or falling) display a notice:
      • "Based on current trend, the flood water will be [higher / lower] than the road after HH:MM pm/am"

Crest Prediction

We want to be able to predict crest timing at a particular gage or area based on the timing of crests at upstream gages.

  • For each gage build a model for each upstream gage that predicts the timing of the gage's crest based on the timing and height of the upstream gage
    • For example, if gage C has two upstream gages, A and B. Build two models. One that predicts the timing of the crest of C based on A and one based on B.
  • Only consider gages from USGS at the falls to USGS at Duvall
  • Formalize the definition of a crest
    • Something like: crest is confirmed after three down readings with no up readings.
    • How do we handle a turbulent gage?
    • How do we calculate the time of the crest? First highest point?
  • Phase I: Height independent. Calculate median time based on past data.
  • Phase II: Try to model hight. Maybe start with simple linear fit.
  • Gage Details page:
    • Show prediction based on nearest upstream gage that has crested
    • Show confidence interval with prediction
    • Example:
      • Estimated crest at Gage C based on observed crest at Gage A: 5:10 pm (+/- 90 minutes)

Flood Forecasting

Model Based Short-term Prediction

Predict the next 4-12 hours at each gage. Most short term (4-12 hrs) flooding impacts in the lower valley will be the result of rain that has already fallen.

We should consider using the following inputs to build a model:

  • Gage trend
  • Upstream readings and trends
  • Upstream major tributary readings and trends (Tolt, Raging, 3 forks)
  • Meteorological readings from various stations in the watershed:
    • Temperature
    • Snowpack
    • Rainfall

Predict the following for each gage:

  • Road crossing time
  • Yellow / Red status change time
  • Crest time
  • Crest height
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