Ryer Island
Index   Historic maps    Wrong_Ryer_maps
Very important governmental reports regarding Delta islands, most notably, the Delta Risk Management Strategy, Phase 1 report, or DRMS, currently provides incorrect data regarding Ryer Island flood history, flood risk and seismic risk.   Here's a table comparing historic Delta Island flood data.  Notice DWR keeps quoting 160 or more floods, but USACE says its more like 37 floods in the Delta since the levees were improved 1917 to 1940's.

So what does this have to do with Ryer Island, just one of the Delta islands affected by DRMS data?  DWR representatives did acknowledge the incorrect data use regarding Ryer Island, and agreed to contact their consultants who did the report, to get it corrected.
Soils and Seismic data reports that confuse the Ryer Islands Ryer Island in the California Delta SHR
We've found at least 17 mistakes in DRMS related to Ryer Island alone!  DRMS was published in "final" form by California's Department of Water Resources (DWR) to validate decisions regarding the future of the Delta, but the underlying Ryer Island historical data is wrong  (see also  DRMSf1_wrong_on_Ryer.pdf) as to inundation history.  For that matter, inaccurate records were found for several other islands in the North Delta Region, but we will leave that issue to another day and forum.  (You can click on the map to the right to see an enlarged version of the a wrong DRMS-URS map completed for DWR for their risk analysis of Sacramento Delta islands.) 

By March 2010, after repeated requests for review and correction,  the new Delta Council is making decisions regarding Delta Islands, based on FALSE information, including the DWR data about Ryer Island.

   Note that on 11-18-09 DWR responded by email, indicating there isn't sufficient funding to correct DRMS Phase 1, so a request was  made to remove the entire DRMS Phase 1 report from any new DWR reports, such as the California Water Plan Update 2009.  See Request  DWR then confirmed again they are having the consultant correct DRMS Phase 1 as to Ryer Island data, and will post the corrections so that other persons or agencies will not continue to utilize incorrect Ryer Island data.  See latest email confirmation.   Examples of other Delta-related agencies or groups currently utilizing wrong Ryer Island data in Delta presentations or reports include Delta Vision, PPIC, UC Davis professors.

 The "Ryer Island mistake" is very important to farmers, residents and businesses of Ryer-now and in the future- because DRMS has been used for the decision process leading up to and including the Bay Delta Conservation Plan (BDCP).   The BDCP is an important legal document currently being utilized to validate substantial proposed changes to use of Delta islands and flow of Delta fresh water.  Take a look at this table comparing the different agencies and organizations who published reports of Delta Island floods over the years.  It appears the USACE (to the far right of the table)  is closest to correct, based on local historical knowledge.  One might assume if DRMS is wrong regarding one large Delta island, that it may also be wrong for other Delta islands.  One might also assume responsible scientists and agencies that want to base decisions on facts would FIRST correct the DRMS before moving forward with modification to the Delta.
 
DRMS Phase 1 Report "Final", which was a collaborative report published by DWR, contains many instances of incorrect raw data used regarding Ryer Island.  Since the raw data is wrong, the resulting calculations for flood history, and flood and seismic risk are also incorrect.  This table provides a partial list of data regarding Ryer Island that needs to be corrected and/or reviewed if more data is required to verify the final numbers.  DWR representatives did acknowledge a recognition of the use of incorrect Ryer Island data, and indicated corrections would be made to DRMS and notices sent out.  See emails. DWR confirms corrections being made  See wrong DRMS maps.

 

 

DRMS Phase 1 Final Corrections Needed-Tables and Figures, by chapter (easy fixes highlighted in yellow)

 

 

DRMS Section

Page or Table

description

Correction 1

Correction 2

 

2

2-2

Towards bottom right, should read "levee failures have flooded Delta islands and tracts 165 or 164 times  (says 166 times)  Fig 2-5

165

163*

 

2

Figure 2-3

Long Point or "the other Ryer Island" is not labeled in the Suisun Marsh area

 

 

 

2

Figure 2-4

Map showing islands reclaimed years.  Ryer island records do not match other historical data on same island reclamation.  Shows as yellow

Dark Green

Light Green

 

4

4-9, 4-10, 4-16

V=frequency of occurrence confirms island inundation data used for calculations

 

 

 

5

Figure 5-1

Map incorrect.  Shows Grand Island southern tip as developed.

Color correction

 

5

 

Figure 5-9

Map of Delta businesses.  Snug Harbor not included, mission

Correction to include

 

5

 

Figure 5-14

Map of Delta Island elevations.  Does not appear to match previous Ryer Island data.  Need verification before challenge

 

 

6

6-23

Formula for seismic probability refers to soil type.  Verify soil type against 1935 soils map for Ryer Island

 

 

6

6-37c

Review data for Ryer Island to verify correct soil type 1935 soils map used for calculations.  Need verification before challenge

 

 

6.

6-36

Ryer Island sandy material reference-compare to 1935 soil type 1935 soils map and other Ryer Island records of levee construction.  Note Dr. Ryer levee footing article.  Map appears wrong

needed

 

7

7-8

Top of page  "since 1900 158 islands have flooded" does not match with section 2-2 nor historical data

 

 

7

7-9

"in 1986 9 islands flooded" should read "8" since reference table lists Ryer Island, which did NOT flood in 1986.

To "8"

 

7

Table 7-9a

Towards bottom:  Lists Ryer Island as flooding in 1986.  This is wrong.  Lists 1904 and 1907 as Ryer flood incidents, but these dates are before current levee was built.  Should say "2, 1 or 0"  (see 7-9b)

2

0

7

Table 7-9a, page 2

Total # of Delta Flooded Islands/Tracts says 158.  Should be 157, 156 or 155

157

155

7

Table 7-9b

Lists Ryer as flooding in 1907 and 1986 "since 1900", which verifies the use of "1" instead of "3" for Ryer Island flood history

1

 

7

Figure 7-19

Map showing  Ryer Island as having 3 historic inundations, when number should be 1 or 0

Color correction to white or light blue

 

7

Figure 7-20

Map listing years and locations of levee failures.  Lists 1986 Ryer Island failure location, even though Ryer Island did not flood and did not experience levee failure

Remove Ryer data from map

 

7

Figure 7-21

Cumulative Number of Levee Failures 1900 to 2006 needs to be corrected to reflect Ryer island data

Correction needed

 

7

Figure
7-22 a&b

Cumulative number of levee failures 1950 to 2006 needs to be corrected to reflect Ryer Island data

Correction needed

 

7

Figure 7-27

Under seepage Vulnerability Classes-challenge map findings if soils types or sandy soil finding is verified as incorrect per 1935 soils map

 

 

7

Figure 7-50

Map of Thickness of organic materials near levee toe.  Verify data prior to challenge.

 

 

7

Figure 7-71

Probability of failure versus vertical exit gradient for under seepage.  Verify data prior to challenge.

 

 

9

Figure 9-2

Locations of Levee Failures.  Lists 1986 Ryer Island as flooded-incorrect.

Correction needed

 

Appendix 12c

Page 11 and 23 of 24

Appears to list Ryer Island as having no risk of life loss even though US Census from 2000 indicates approximately 300 residents of Ryer Island

Verification needed

 

Appendix 12B

Page 36 of 38

This table indicates Ryer Island has a day or night time population of between 1 and 16 persons, contrary to local knowledge and 2000 US Census that shows approximately 300 residents for Ryer Island

Verification needed

 

13

Table 13-3

Challenge Ryer Island  mean rate of failures, etc, due to incorrect underlying data use regarding flood history

Correction needed

 

13

Table 13-6

Challenge Ryer Island failures calculations due to incorrect underlying data use regarding flood history

Correction needed

 

13

Table 13-8

Challenge Ryer Island calculations due to incorrect underlying data use regarding flood history

Correction needed

 

13

Figure 13-5

Table needs correction to summarize change due to Ryer Island data correction

Correction needed

 

13

Figure 13-7

Map of mean Annual Frequency of Failure.  Appears wrong as to Ryer Island, which should be light green, not dark green.  The other Ryer Island is missing*

Correction needed to lt. green

 

13

Figure 13a

Map of Mean Annual Frequency of Failure.  Appears wrong for Ryer Island.  Should be light green instead of Dark green

Correction to Ryer to lt. green

 

13

Figure 13-16

Map of Mean Annual Frequency of Failure.  Ryer Showing as 3-5% in yellow and should be in light green at <1% or Dark green if 1-3%

Correct Ryer to lt. green

 

DRMS

Figure 5

Map labeled DRMS Geomorphic Review "Map of the Modern Delta"  labels Steamboat Slough as the "Sacramento River"

Correct river names needed

 
DRMS Geomorphology Page 33 http://www.water.ca.gov/floodmgmt/dsmo/sab/drmsp/docs/Geomorphology_TM.pdf
labels Steamboat Slough as "Sacramento River"		 correct river names  

DRMS

Executive Summary

Phase 1 Executive Summary repeats totals from sections as noted above, so where those totals have changed to reflect Ryer Island data correction, the Executive Summary should also be corrected.

*