.22 2:1: sit" FRI 12:25: p,e OF FORT PEND Engineering Department 1124 Blame Road R0. Box 1?49 Texas 77471-1449 Phonc: (71313424039 July 6, 1992 The Honorable Roy L. Cordon, Jr. 9 Fort Bend County Judge 309 South 4th Street 7th Floor Richmond, Texas 77469 Re: Barker Dam - Possible Flooding o1 Non?Government Owned Land kw ?Au- ulna-.45..- Dear Judge Cordes: While in a meeting last week with Mr. Richard Long, Barker/Addicks Reservoir Manager with the Galveston District, U.S.Army Corps of Engineers concerning the Fort Bend County Cinco Ranch Park and the YMCA Day Camp Facility, the issue or intermittent inundation or flooding within the Corps? Barker Reservoir was discussed and I was made aware of some recent statistics which could have a: major impact on the County. The attached data sheet, labelled "Noteworthy Pools - Addicks Barker Dams", is a listing of water surface elevations behind the dams. Please direct your attention to the second grouping for "Barker Dam". The earliest date listed is for the May 15, l968 reading which has a footnote delineating that the original water surface elevation of 94.60 MSL was changed to 92.69 to reflect the 1973 v.5. Coastal Geodetic Survey (USCGS) adjustment. Basically, this means that the elevation of the USCGS Survey Marker that was used for this area i had subsided 1.71 feet resulting in the adjusted elevation of 92.89 man. This follows true with the subsidence data that eventually in. 3 led to the creation of the Fort Bend Subsidence District. Watershed area could possibly be a contributing factor to the portion of the data that concerns me the most. The last 2 lines of the Barker data are labelled GOL 97.30 (maximum possible pool elevation contained within Government?Owned Land) and MAX POOL 106.00 (maximum possible pool elevation before water is spilled around the ends of the dam}. Comparing these two elevations it becomes evident that the Barker Dam was designed and/or modified to This 8.7 feet of water translates into the flooding of approximatelg 4,679 acres of land, not under jurisdiction of the Corps of Eng nears. From the Corps data, it appears that when the Government owned land is completely oovared with water, the Reservoir has only reached 39.9% of its designed capacity. These 4,679 acres or privately held land are located in one of the fastest growing areas shared by Fort Bend and Harris Counties, the Cinco Ranch and Kelliwood Developments. 30 '92 NDTEUURTHY POOLS 1. 000105 a 130pr0 00119 00011310; 0011 SURPRISE 012150 0013mm :0 2: 2: 1301301211? 0015 11-1 001225 ems-Farm) 110x FOCUS-D 01-" 001-114) 9 0012 '92 100.58 0,446 57,955 23.9 49-8 15 my '00 90-20 (5) - .. .. 4 .31 6.33? 34.349 12.1 29-5 .20 01:12 '91 96.?8 5,9?1 30.?15 15.3 25-4 106- 10 12.450 110.253 9 100. 0 1 00x 112.00 16,423 200,040 100.0 000K150 0911 511121301: HPEH 0013001111 111 120900er 2: mpacrw 001E 03101101111) 01 01312155 110x 11001.13) 001-(41 5 11012 '92 95.89 11.330 66,910 32.0 00-2 20 01312 '91 93.63 10.1?9 42.4?0 20.3 50-9 15 1101' '53 92.09 (5) .- .- 4 SEP '31 92.3? 8.653 30.413 14.6 36.5 a 1301-01 9?-30 12.050 03.410 39-9 100-0 .1 110x PDUUBJ 16,739 209.000 100.0 a: non-:5: 1L (1) 050011005 CF UHTER sum-'01: HRE IN 11973 00015011311111- 121 ONE DF 00032 IS ONE HERE 01: um, ONE FUUT DEEP- 13) PERCENT OF 120130811? 0F 11010111111 POSSIBLE P001. BEFORE 1.1mm IS SPILLED 0900110 ENDS CF 0011. 1; 14) PERCENT OF 00mm? 0F 1101011011 POSSIBLE P001- 1201101111an 01011111 1-0110- (51 001011101. RBIHTIDN 01-- 100.03 1151. 00mm 10 REFLEIZT 1973 003050100. 1 15) 001011101. 151-5007113111 0F 94-50 1151. 00.105050 REFLECT 1973 00.1051112111- 11011111011 POSSIBLE P001. 0011101qu 011111111 swmmem?umen 1.0110- 3 .. (8) 0011mm POSSIBLE PUDL BEFORE UHTER 15 SPILLED THE ENDS OF THE 00115. 0. . . xi: r-?Rz 12:54 The unofficial report from the Corps in that if 4" of additional rainfall had hit the watershed on the March 6, 1992 (elev. 95.89) event, there would have been floodwatera inside of reeidencee located in development: adjacent to the Reservoir. with the rim or one of. the Barker Dem (constructed early 19409) bei? tempt-Etna central Houston from flooding eituatione, it seems unlikely that the Corps would consider loWering the Dam, on eciall after recently epending approximately $15 ndllion to raEae an strengthen the main ortione of the Dam. A more realiatic alternative would be a uy-out' of additional privately- held land subject to possible inundation due to the Dam. MW been generated released to the public without drawing too "111' uc? .18 true that e? Wem?servoir were on one under extreme criteria. and hypothetical ecenarioe, recent rainfall events and weather- conditiona have shown that many areas previously considered relatively safe from rising Waters have been flooded. Certainly additional data and studies will be required to determine the actual existence of/or extent of any problem with encroachment on privately held land. It is my personal opinion that Fort Bend County and the development community be involved the Corps on this situation. During our meeting I got the fee ing that this attitude was also reflected by Mr. Long and the Corps. Should you have any questions about this information, please call me. Copies of the data sheet have also been given to Dan Gerken and Ron Drachenberg. .Sincerely, WJAM Charles Glen Crocker Assistant County Engineer . encloeure cc: Commissioner Bud O'Shielee Commissioner Grady Frontage Commissioner Alton Preaaley Commissioner Bob butts Hr. Den Gerken, Drainage District Mngr. Mr. Ron Drachenberg, County Engineer Mr. Sid Shaver, Floodplain Administrator Hr. Mel Speed, Emergency Management Coords b, PO. Box 130089 TurnerCollieCd Braden lnc. 7t] 780-4l00 Fax Pl} Pall-0838 Engineers Planners 0 Project Managers November 20. 1992 Board of Directors Willow Fork Drainage District Clo Vinson 6: Elkins 3300 First City Tower 1001 Fannin Houston, Texas 77002?6760 Attention: Mr. Joe B. Allen Re: Letter of July 6, 1992 relating to Barker Dam - Possibility of ?ooding non government land Gentlemen: We have been provided a copy of the referenced letter wherein the several statements made concerning the construction and operation of the reservoir, the recent rains experienced in the ff Buffalo Bayou watershed, and subsidence collectively infer properties upstream of Barker {it Reservoir may be subject to ?ooding. Concern has been expressed that the facts presented in the letter could unnecessarily adversely impact sales of land in the high quality residential neighborhoods currently being developed in Fort Bend County. In response we wish to offer the following comments that should be considered as further defining the actual situation in the watershed. Flood Protection above Barker Reservoir compared to other areas The developing neighborhoods upstream of Barker Reservoir have been designed to exist as high quality developments with a level of ?ood protection that meets or exceeds the requirements of the Federal Flood Insurance program. The residential and commercial properties in Cinco Ranch have all been ?lled to an elevation at or above the 100-year flood pool elevation of Barker Reservoir as established by the Federal Emergency Management Agency (FEW) and the U.S. Army Corps of Engineers. Structural slabs have typically been set 12 to 18 inches above ground level, thus providing even additional protection against ?ooding. The Fort Bend Drainage District now requires that slab elevations be set to a minimum of 100.4, or 2.6 feet above the loo-year pool level of Barker Reservoir. To our knowledge this level of flood protection is equal to or better than the level of protection provided by a series of channels and levees that protect the majority of recent development throughout Fort Bend County. It should also be stressed that the 100-year ?ood elevation is a national standard for flood protection by FEMA. FEMA established this standard as a reasonable balance of economics and safety. The areas upstream of Barker reservoir are at least as much or more protected [rorn flooding as other areas. A parallel to expressing concern for ?ooding levels in Barker Reservoir of more than loo-year frequency is to express concern for ?ood levels along the Brazos River of more severe than IUD-year frequency overtopping the levees that protect many developed areas of the county. TEXAS nus I i DALLAS I FORT WORTH HOUSTON COLORADO DENVER Turner Collie?? Braden Inc. November 20, 1992 Board of Directors Willow Fork Drainage District Page 2 Barker Reservoir was constructed in the 1940?s. The level of flooding of government property that occurred in March 1992 was the highest recorded in the 50 year histOry of the dam. In spite of this long history, ?ood levels in Barker Reservoir have never exceeded beyond the limits of Government Owned Land (COL). This history includes the intense rains of 1957 and 1979 that resulted in extensive flooding along the Brazos River and the greater Houston area. The ?ood levels in March 1992, despite being the highest of record, still left 20 percent of additional capacity in the reservoir within the COL. Subsidence and Storage in Barker Reseroeir The letter states that 1.71 feet of subsidence has occurred in the area of Barker Reservoir. The letter does not state that this subsidence increases as one moves further to the east.ln 1986 a study was performed jointly for Fort Bend County, Harris County, the Harris Galveston Coastal Subsidence District, and the City of Houston to eXamine the relationship between subsidence and flooding. One section of the study dealt speci?cally with Barker Reservoir. The study evaluated the impact that existing subsidence has had on the design storage-capacity of the reservoir. It showed that, at the 100-year pool level of 97.8 feet, National Geodetic Vertical Datum (NGVD) the capacity of the reservoir has actually been increased. That study also concluded that conditions of subsidence that tilt from west to east (as has actually occurred), has the impact of storing more water within the GOL. The limit of COL is roughly along the line of 97.3 feet (ngvd, 1973 adjustment) meaning that some land outside the COL will be inundated when the IOU-year pool elevation in Barker reservoir is realized. However, this factor has been considered in the planning and design of the neighborhoods, particularly Cinco Ranch, so that it does not impact develOped preperties. gestation of the Dam and Elevation of the IOO-yeer ?ood pool The letter states that the elevation of COL is roughly 97.3 and the max pool elevation is 106.0, concluding that the Reservoir is actually designed to contain water to the 106.0 elevation. The max pool elevation is not the design capacity of the reservoir. Reservoirs are constructed according to standard factors of safety. These factors included constructing the dam height to an elevation above the design pool elevation. The purpose of this practice is to provide safety factor against life threatening events caused by a dam failure. These standards were adopted in part as a result of the Johnstown ?oods that killed several hundred people when dams were over topped and breached causing a wall of water to accelerate The height of the darn above the design pool elevation varies depending on the potential damages that would be caused in the event of a dam breach. Obviously that condition is very severe in the case of Barker Reservoir and the dams are raised signi?cantly above the design pool elevation. November 20, 1992 Board of Directors Willow Fork Drainage District Page 3 Qgsign gnagg'w of the Hegemon- The letter states that the total volume of water that can be stored on government owned land is only 39.9% of the design capacity of the reservoir and that 4,679 acres of property in Fort Bend County will flood before the dam is overtopped. The two elevations referenced are 97.30 feet (as ?ooding capacity of COL) and 106.00 feet as the maximum flood pool. As previously stated the maximum ?ood pool of a reservoir is not its design capacity. It is instead a requirement to maintain safety of the darn structure. Rainfall and Volume of Rung?f The letter states that an unofficial report states that if an additional 4 inches of rainfall had occurred on March 6, 1992, the ponding level in Barker Reservoir would have extended to private properties and flooded houses. Despite discussions with the Corps of Engineers, Galveston District we have been unable to obtain a copy of any report that references this statement and do not know the basis for such a calculation. As stated previously, the structures in Cinco Ranch are all elevated above the level of the IOU-year pool in Barker Reservoir. Censequently they are also elevated above the limit of ?ooding of GOL. Additional ?ooding beyond the COL does not necessarily mean that flooding of houses in Cinco Ranch would occur. The level of pending in the reservoir is a function of rainfall and operating procedures of the reservoir. Since typically the opera ting procedures cause the reservoir to take longer to drain than it does to fill, the design usually considers the probability of long term combinations of rainfall events. The 100-year regulatory floodplain elevation established by the FEMA supposedly considers the combination of rainfall probabilities and operating procedures. This elevation, published in 1985, established this elevation as 97.8 feet (ngvd) A large amount of rainfall occurred in the Houston area in the ?rst three or ?ve) months of 1992. Without statistical analysis we are unable to say what the frequency of such a volume of rainfall over that time period was. We also can not say what the frequency of likelihood of receiving an additional 4 inches of rainfall would have been on March 6. If that probability is one percent or less, then the design pool level of the reservoir is appropriate as was the regulatory ?oodplain elevation established by FEMA. -.-- n- . Turner Collie?j Braden Inc. November 20, 1992 Board of Directors Willow Fork Drainage District Page 4 Purchasing Property in Fort Bend Camry At issue may be the changes in operating procedures to Barker Reservoir dam since the Reservoir was constructed in the 1940?s. We wholeheartedly support a reevaluation of these operating criteria to ascertain protection of all properties that the darn influences. However, to assume that the US. Army Corps of Engineers would purchase private property in Fort Bend County seems to be premature without supporting documentation from their office. To determine what if any modi?cations to the reservoirs and/or operating procedures are appropriate will require extensive engineering and economic studies. Representatives from the the Corps of Engineers stated they have requested funding from Congress to perform the appropriate analysis. We have interpreted the tone of the July 6, 1992 letter authored by Fort Bend County to infer that the properties immediately upstream of Barker Reservoir are in imminent danger of being ?ooded and that the level of protection from ?ooding is not as secure as anticipated. It is our opinion, based on review of related documents prepared by FEMA, the Corps of Engineers, and our own investigations, that the properties within the Willow Fork Drainage District are well protected from individual storm events and/or pending levels in Barker Reservoir that have a 1 percent or greater chance of occurring. To the best of our knowledge, this level of protection meets the requirements of all permitting agencies and mortgage lending institutions. Very truly yours, Michael B. Hunn, P.E. Division Director, Land Development FORK DRAINAGE DISTRICT December 29, 1992 The Honorable Roy L. Cordes, Jr. Fort Bend County Judge Fort Bend County Courthouse 309 South Fourth, Suite 719 Richmond, Texas 77469 Re: Letter of Glen Crocker, Assistant Fort Bend County Engineer, dated July 6, 1992 Dear Honorable Judge Cordes: We have been provided a copy of a letter from Glen Crocker, Assistant Fort Bend County Engineer, dated July 6, 1992, which discusses the potential ?ooding of property upstream of the Barker Reservoir. Willow Fork Drainage District (the ?District") was shocked by the conclusions and assertions made by Mr. Crocker. Because of the extremely serious nature of his allegations, and the potential liability of Fort Bend County, Fort Bend County Drainage District and the District to homeowners in this area, we requested the District?s engineer, Turner, Collie Braden, to investigate Mr. Crocker?s claims. A copy of their response is attached. Based on Turner, Collie Braden's analysis and further investigations by the District, we have reached the following conclusions: 1. Mr. Crocker?s conclusions were made without the bene?t of adequate research, independent veri?cation or proper scienti?c methodology; 2. We are surprised that Fort Bend County would allow someone who is not a registered professional engineer (as verified on December 17, 1992 with the State Board of Registration for Professional Engineers) to use Fort Bend County letterhead to make such baseless, unfounded . and potentially damaging assertions without the bene?t of research and consultation with others who perhaps are more familiar with this extremely complex drainage system. As you know, this correspondence is a public record, and could place Fort Bend County or Fort Bend County Drainage District at signi?cant risk of liability should the obvious fallacies of this letter not be revealed; and viDecember 29, 1992 Page 2 3. We are unable to locate anyone with the Corps of Engineers, the operator of the reservoir, who will con?rm the allegations in Mr. Crocker?s letter that 4" of additional rainfall would have resulted in "?oodwater inside of residences located in development adjacent to the Reservoir." If a report con?rming such analysis or a competent professional reached such a conclusion, we request that the report or person be made known to the District. Otherwise, the District can only assume this assertion was more speculation and not based upon adequate investigation. An analysis of the ?ood potential behind Barker Dam is an extremely complex matter. m. you know, Fort Bend County Drainage District and the District have given approval to build based upon FEMA ?oodplain maps. We assume that Fort Bend County believes that the FEMA 100 year floodplain maps are presently correct. If not, we assume that you have advised FEMA and the District of that conclusion. The District respectfully requests Fort Bend County to make a thorough investigation of Mr. Crocker?s letter and advise the District of your ?ndings. Please provide the District with copies of any future correspondence regarding this matter. Thank you for your attention to this matter. Very truly yours, George E. ilsson President Willow Fork Drainage District 105 9:2?35 cc: Honorable Alton Pressley Honorable R. L. O?Shieles Honorable Grady Prestage Honorable Bob Lutts Mr. Charlie Leyendecker Mr. Jim Box Mr. Larry Lippincott Board of Directors of illow Fork Drainage District Mr. lkins . Qlive [Turner, llie Braden] (I. (keg/Jr TurnerCollieCd Braden lnc. art's-litters HOUSTON, TEXAS F7219 5?5? WWDWAY i?lJ ?80~il00 November 20, 1992 mix F74183TCBHUL- FAX 713 TED-0530 Willow Fork Drainage District c/o Vinson 6r Elkins 3300 First City Tower 1001 Fannin Houston, Texas 77002-6760 Attn: Mr. Joe B. Allen Re: Willow Fork Drainage District Letter from Fort Bend County Drainage District dated September 2, 1992 Regarding Willow Fork Dear Mr. Allen: We are in receipt of the attached letter from Fort Bend County Drainage District dated September 2, 1992 regarding drainage capacity in Willow Fork of Buffalo Bayou within Cinco Ran ch. In response, we wish to offer the following comments. Channel improvements were constructed and completed on Willow Fork of Buffalo Bayou within Cinco Ranch in 1986-1987. The improvements were designed in accordance with a Master Drainage Plan for Willow Fork Drainage District which was approved by Fort Bend County. The channel improvements were designed to provide adequate drainage capacity to serve all proposed development within Willow Fork Drainage District and the Via Ranch No. and also the upstream watershed in the state of development existing at that time. The construction work was completed in general conformance with the approved Plans and Specifications. Record drawings based on as-built information provided by the construction contractors were transmitted to Fort Bend County at the same time they were submitted to FEMA after construction was completed. The total acreage within Willow Fork Drainage District is about 5700 acres, of which only approximately 600 acres have been developed. The majority of this developed acreage (about 500 acres) outfalls into Willow Fork of the area addressed in the letter. The total acreage within the Via Ranch WCID No. 1 is about 1700 acres. It is our understanding that none of this District has been developed. The County's concern for drainage capacity is based on 2 field cross?sections taken within 500 feet of each other. Willow Fork channel extends for more than 3 miles through the Willow Fork Drainage District. Because the two cross sections were taken so close together, they likely do not reflect the condition of the channel along the entire reach. TEXAS AUSTIN AS 1' HOUSTON COLORADO Turner Collietfb?Braden lnc. November 20, 1992 Willow Fork Drainage District Attn: Mr. Joe B. Allen Page Two 5. The location of the 2 cross-sections addressed in the letter is immediately of the Grand Parkway crossing of Willow Fork, Based on our discussions with the Cinco Ranch Field Personnel, the contractor for the Grand Parkway constructed several low water crossings across Willow Fork in this area during the course of his construction which is still ongoing. 6. In the attached letter agreement executed by Fort Bend County Drainage District on October 10, 1988, Fort Bend County Drainage District accepted Willow Fork for permanent operation and maintenance. On the basis of this information, we recommend that Willow Fork Drainage District request that Fort Bend County Drainage District provide the required maintenance on any silted or eroded areas on Willow Fork so that drainage capacity is maintained for development within Willow Fork Drainage District and the Via Ranch WCID No. i. If you have any questions or need any additional information, please call. Very truly yours, ?Esp,th L63 Rebecca (3. Olive, P.E. Project Manager Attachment c: Board of Directors, Willow Fork Drainage District Via Ranch WCID No. 1, do Mr. Ralph Wissel, Costello Inc. 1? ,i i? it". of r. 0. Box in 'd 10015 E. 5m 972mm Mme. rm: mo 4 Can!) [My mum: Mow/um os- FORT Ben October 10. 1988 Willow Fork Drainage District c/o Vinson and Elkins 2800 First City Tower Houston. Texas ?7003-6780 Re: Willow Fork of Buffalo Bayou VA I Gentlemen: Fort Bend County Drainage District (the "Drainage District?) recognizes that Willow Fork Drainage District (With contributions from Via Water Control and Improvement District, Cinco Ranch Venture and Cinco Ltd.) have constructed major improvements to the Willow Fork of Buffalo Bayou VA, Station 3+84.61 to 305+73 in accordance with plans and specifications approved by the Drainage District. These improvements are now complete and meet Drainage District standards for acceptance by the Drainage District for permanent operation and maintenance, except for certain deficiencies, primarily willow trees within the channel. Subject to your payment of $20,000 to the Drainage District to remedy these deficiencies, the Drainage District 34 hereby accepts all improvements. channels, facilities and rights-of?way of the Willow Fork of Buffalo Bayou Station 3+84.61 to Station 305+73 for permanent operation and maintenance and assumes all responsibility for correcting the deficiencies and Willow Fork Drainage District (and Via Water Control and Improvement District, Cinco Ranch Venture and Cinco Ltd.) shall have no further responsibility for the deficiencies or future operation and maintenance. Please indicate your acceptance by executing below and remitting Payment. This agreement was approved by the Drainage District Board at its Willow Fork Drainage District October 10. 1988 Page 2 meeting on October 10. 1988. . 4d?; Jo 19 E. Stavinoha. County Judge Dianne Wilson County Clerk and Ex-Officio Clerk of the Commissicners Court of Fort Bend County. Texas (SEAL) Accepted this 43 day of October, 1988 Willow Drai ?e Dist ict By- Presxdent, rd of Blrectors Attesp: Secretary. Ban5 of Diregtors WILLOW FORK DRAINAGE DISTRICT December 29, 1992 Mr. Mark Vogler Assistant Engineer Fort Bend County Drainage District PO. Box 1028 Rosenberg, Texas 77471 Re: Capacity of Willow Fork of Buffalo Bayou at Cinco Ranch Dear Mr. Vogler: By letter dated September 2, 1992, you expressed concerns about the drainage capacity which currently exists in Willow Fork of Buffalo Bayou. We have requested that the District?s engineers, Turner, Collie Braden, review your letter. Their response is attached. Based on the information provided by our engineers and the agreement between the Fort Bend County Drainage District and Willow Fork Drainage District, we request that Fort Bend County Drainage District immediately provide the required maintenance to this channel to ensure that development may continue in this District without the necessity of detention or maintenance work by Willow Fork Drainage District. Very truly yours, George Nilsson President, Willow Fork Drainage District i656? Inlmgi 3.02 cc: Honorable Alton Pressley Mr. Charlie Leyendecker Mr. Jim Box Mr. Larry Lippincott Board of Directors of Willow Fork Drainage District Mr. Joe B. Allen [Vinson Elkins Ms. Rebecca G. Olive [Turner, Collie Braden, Ina]