Difference between revisions of "Flood Forecasting"

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Our current plans for flood forecasting involve three phases:
 
Our current plans for flood forecasting involve three phases:
  
−
#Short-term prediction
+
#Short-term trend extrapolation
 
#Crest prediction
 
#Crest prediction
−
#Flood forecasting
+
#Short-term forecasting
  
 
===Short-term Prediction===
 
===Short-term Prediction===
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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.
 
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 =====
+
=====Linear Trend Extrapolation=====
  
−
* On the gage details page
+
*On the gage details page
−
** Create extrapolated readings every 15 minutes from the last reading until last reading + 6 hrs.
+
**Create extrapolated readings every 15 minutes from the last reading until last reading + 6 hrs.
−
** Show extrapolated readings on chart with a different color.  
+
**Show extrapolated readings on chart with a different color.
−
** If extrapolated readings cross a road (rising or falling) display a notice:
+
**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"
+
***"Based on current trend, the flood water will be [higher / lower] than the road after HH:MM pm/am"
 +
 
 +
*
  
 
===Crest Prediction===
 
===Crest Prediction===
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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.
 
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 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
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** 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.  
+
**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
+
*Only consider gages from USGS at the falls to USGS at Duvall
−
* Formalize the definition of a crest
+
*Formalize the definition of a crest
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** Something like: crest is confirmed after three down readings with no up readings.
+
**Something like: crest is confirmed after three down readings with no up readings.
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** How do we handle a turbulent gage?
+
**How do we handle a turbulent gage?
−
** How do we calculate the time of the crest? First highest point?  
+
**How do we calculate the time of the crest? First highest point?
−
* Phase I: Height independent. Calculate median time based on past data.
+
*Phase I: Height independent. Calculate median time based on past data.
−
* Phase II: Try to model hight. Maybe start with simple linear fit.  
+
*Phase II: Try to model hight. Maybe start with simple linear fit.
−
* Gage Details page:
+
*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)
  
−
<br />
+
===Flood Forecasting===
  
−
===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.
  
−
Long-term, we want to build a model using all of the possible inputs that might have an effect on water level.  Examples:
+
We should consider using the following inputs to build a model:
  
−
*Weather forecasts
+
*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
 
**Rainfall
−
**Temperature
 
  
−
Using this model, we want to be able to try to predict water levels well in advance of flood events.
+
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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