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Project Plan:

Start Date: September 18, 2001

Status: All values calculated for 705 sites of August 8, 2002

Projected End Date: Pending implementation of calculated values into Informix database and preparation of completion report, also it is planned that values will be submitted to Service Hydrologist and Hydro Focal Points for review.

Abstract:

Phase I of this project consisted of calculating Flood Stages/Flows, Moderate Stages/Flows, and Major Stages/Flows for all sites without these values reported in an E19. Phase II of this project consisted of calculating Bankfull Stages/Flows, Screen Stages/Flows, Screen Rates (Stages/Flows), and Significant Rates (Stages/Flows) for all sites. Phase III consisted of calculating "Ultimate" Screen Stages/Flows, "lower" Screen Rate Flows, and "higher" Screen Rate Flows for all sites. Throughout this process I have tried to be conservative and internally consistent. The process has been reiterative in that if one value was changed, then all other values for that site were rechecked. For the 587 natural sites (no E19 values), the flows are more accurate than stages. The biggest uncertainties were drainage areas for non USGS sites, and the rating curves. At 106 sites I found the rating curves to be questionable. At 102 additional sites I found "GUIRT" (a local rating table application) was not useful above the rating. However, I found extending the rating curves through flow of record useful at 28 sites and I developed synthetic rating curves for 83 sites. At 17 sites I used Flood Control District of Maricopa County calculated return intervals and their rating tables. Elsewhere, I used my best judgment to deal with these uncertainties. In some cases I assumed that two or more sites were the same, or had like characteristic. I have tried to document the changes in JMP using the "rating curves" or "value quality" column.

For Phase I: The first step was to calculate return intervals using the methods described in USGS Water-Supply Paper 2433, much of this work had been previously done. The second step was to develop a river continuum for each value of interest and to adjust the values for basin consistency. Using the return intervals, a correlation between interval and selected event was established. It should be noted here that the derived values were for "natural conditions." Once a stage or flow was derived, the counter part was determined from a rating table or a synthetic rating table was created (see individual explanations below for more details). Phase II was an easy extension of the process used in Phase I to calculating Bankfull Stages/Flows and then calculating additional values using equations (see individual explanations below). Phase III used the concept of maximum floodflows described in USGS Water-Supply Paper 1887 to help define site specific Stages/Flows that could not occur.

Individual explanations for all values:

* 705 sites -- Flood Stages complete (118 from E19s or Emails, 587 calculated from rating tables or estimated using median flood stage for similar size basins within return interval region)

* 705 sites -- Flood Flows complete (118 calculated from rating tables, 587 estimated using return interval or river continuum methods)

* 705 sites -- Moderate Flood Stages complete (10 from E19s, 695 calculated from rating tables or estimated using incremental stage increase method)

* 705 sites -- Moderate Flood Flows complete (10 from rating tables, 695 calculated from rating tables or estimated using return interval or river continuum methods)

* 705 sites -- Major Flood Stages complete (10 from E19s, 695 calculated from rating tables or estimated using incremental stage increase method)

* 705 sites -- Major Flood Flows complete (10 from rating tables, 695 calculated from rating tables or estimated using return interval or river continuum methods)

* 705 sites -- Bankfull Stages complete (60 from E19s, 20 from Flood Control District of Maricopa County, 625 calculated from rating tables or estimated using median bankfull stage for similar size basins within return interval region or estimated using variations of incremental stage decrease method)

* 705 sites -- Bankfull Flows complete (80 calculated from rating tables, 625 calculated from rating tables or estimated using return interval or river continuum methods)

* 705 sites -- Screen Stages complete (all calculated by using variations of incremental stage increase method, checked against the flood of record stage if reported, and the 100 year flood stage)

* 705 sites -- Screen Flows complete (all calculated from rating tables, checked against flood of record flow if reported, and the 100 year flood flow) * 705 sites -- Screen Rate Flows complete [ calculated for 1 hour time period using the formula: screen_rate_q = (screen_q)/3 ]

* 705 sites -- "Lower" Screen Rate Flows complete [ calculated for 15 minutes time period using the formula: lower screen_rate_q0 = [(sig_rate_q)+(screen_rate_q)]/2 ]

* 705 sites -- "Higher" Screen Rate Flows complete [ calculated for 6 hours time period using the formula: higher screen_rate_q2 = (screen_q)/2 ]

* 705 sites -- Screen Rate Stages complete [ calculated using the formula: screen_rate_hg = (screen_hg)/2 ] formula preferred to using rating tables

* 705 sites -- Significant Rate Stages complete [ calculated using the formula: sig_rate_hg = (screen_rate_hg)/2 ] formula preferred to using rating tables

* 705 sites -- Significant Rate Flows complete [ calculated using the formula: sig_rate_q = (bank_q )/2 ]

* 705 sites -- Ultimate Screen Stages complete [ calculated from rating tables ]

* 705 sites -- Ultimate Screen Flows complete [ Twice the Screen Flow used for sites with drainage areas less than or equal to 10 square miles; the formula, ultimate = 8700 times ln(drainage area) + 15000, was used for sites with drainage areas between 10 square miles and 50 square miles; and the formula, ultimate = 64000 times ln(drainage area) - 200000, was used for sites with drainages areas greater than or equal to 50 square miles. For urban basins between 10 square miles and 70 square miles the formula, 12400 times ln(drainage area) + 18000 was sometimes used. ]

* 28 sites -- Rating Curves extended through flow of records or adjusted above rating and saved in Excel

* 83 sites -- Synthetic Rating Curves developed and saved in Excel

* 102 sites -- Rating Curves modified but not saved

* 328 sites -- return interval recalculated or adjusted using river continuum method