WAY Svat te fot Or tf} Coast & ng Ke Pt oe eae MP 1 -70 EXPERIMENTAL DUNES | OF THE TEXAS COAST by Bard O. Gage MISCELLANEOUS PAPER NO. 1 - 70 JANUARY 1970 Wie aine & Lor | APR 141970 i f NOS ; toy | U. S. ARMY, CORPS OF ENGINEERS — + COASTAL ENGINEERING Yso RESEARCH CENTER US ve. \-70 This document has been approved for public release and sale; its distribution is unlimited . Reprint or republication of any of this material shall give appropriate credit to the U. S. Army Coastal Engineering Research Center. Limited free distribution within the United States of single copies of this publication is made by: Coastal Engineering Research Center 5201 Little Falls Road, N.W. Washington, D. C. 20016 The findings in this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents. MIN il vi 0 MN EXPERIMENTAL DUNES OF THE TEXAS COAST by Bard O. Gage MISCELLANEOUS PAPER NO. 1 - 70 JANUARY 1970 U. S. ARMY, CORPS OF ENGINEERS COASTAL ENGINEERING RESEARCH CENTER This document has been approved for public release and sale; its distribution is unlimited . ABSTRACT Storms and increased habitation on barrier islands have reduced the height and width of dunes on the Texas Coast, thereby exposing it to the surges and waves produced by tropical storms in the Gulf of Mexico. This publication reports on experimental means of creating and sta- bilizing sand dunes to protect the coast. Four locations were selected; the SW end of Galveston Island, Packery Channel, Newport Pass on North Padre Island and Corpus Christi Pass. Low areas of the barrier islands were planted in various types of vegetative cover in an attempt to establish dunes without the aid of sand fences. Snow fencing was used to accumulate windblown sand and vegeta- tive planting made to stabilize dunes. Junk car bodies were placed in line parallel to beaches and used instead of more conventional means to establish and stabilize dunes by trapping sand. Since snow fences are more effective and much cheaper, junk cars are not recommended for building dunes. FOREWORD CERC has a program to collect data to enable coastal engineers to stabilize existing dunes and to build artificial ones as protective structures. This paper is published to give wider dissemination to significant information on dune ''growing'". The sand dune experiments and data collections were conducted by the author, Bard O. Gage, a planning engineering in the Coastal Studies Section of the Galveston District, Corps of Engineers. At the time of publication, Lieutenant Colonel Edward M. Willis was Director of the Center; Joseph M. Caldwell was Technical Director. NOTE: Comments on this publication are invited. Discussion will be published in the next issue of the CERC Bulletin. This report is published under authority of Public Law 166, 79th Congress, approved July 31, 1945, as supplemented by Public Law 172, 88th Congress, approved November 7, 1963. CONTENTS INTRODUCTION EXPERIMENTAL SITES STUDY DESCRIPTION VEGETATION SUSPENSION AND RESUMPTION OF EXPERIMENTS CONCLUSIONS ILLUSTRATIONS Figure I Ze Aerial Photograph of San Luis Pass Aerial Photograph of noc: Channel, Newport Pass, and Corpus Christi Pass ai eps Pe CHO Wind rose showing sand-moving winds in the four study areas Sand-fence installations and resulting dunes, San Luis Pass Sand accumulation at San Luis Pass Sand-fence installations and resulting dunes at Packery Channel Sand accumulation at Station 7+00 at Packery Channel Sand accumulation at Station 13+00 at Packery Channel Sand-fence installations and resulting dunes at Newport Pass Sand accumulation at Station 8+00 at Newport Pass. Sand accumulation at Station 14+00 at Newport Pass Car-body and sand-fence installation at Corpus Christi Pass Sand accumulation at Station 3+60 at Corpus Christi Pass Sand-fence installation at Corpus Christi Pass iti Page 15 18 20 Figure V5). 16. Wn 18. OR 20. Zale Die OSG 24. 25k 26. Zi 28. 29. San San San San San NE, Luis Luis Luis Luis Pass - Pass - Pass - Pass - ILLU April May 19 Septem Octobe Luis Pass - August showing sand fence San Luis Pass - August Packery Packery Packery Packery Packery Station Newport Channel Channel Channel Channel Channel ZOO! - July - July - July - Octo - Apri STRATIONS (continued) 1965 - From Station 1500 . 65 - from Station 500 ber 1965 - from Gulf side r 1965 ~ from about Station 750 1966 - from about Station 800, looking ae CumuUlia tal On wail eha hice ree tnicer ne neenes 1966 - looking SW . 1965 - looking NE. . 1966 - from about Station 470 . 1966 - from Station 1800 ber 1966 - same as Figure 23 . 1 1967 - looking SW from about Pass - March 1966 - Plot of American beachgrass just after planting SP ti lictiheh i: Newport Pass - July 1966 - Same as Figure 16, showing survival of American beachgrass after 4 months Newport Pass - Newport Pass - Corpus Christi Corpus Christi Corpus Christi Corpus Christi 6 months later. July 19 April 1 Pass - Pass - Pass - 66 - looking SW:-from about Station 1300 967 - looking SW from Station 1600 July 1965 - looking NE across Pass September 9 6 Siem ei sematts September 1965 - looking northwest . Pass - March 1966 - same as Figure 32 TYPICAL SAND ACCUMULATIONS Page 21 21 22 22 DiS 23 24 24 25 25 26 26 1. INTRODUCTION During April 1965 the Galveston District, Corps of Engineers, began experiments to determine the practicability of creating and stablizing sand dunes on low areas of the barrier islands of the Texas coast. The work was in connection with preliminary studies to provide hurricane flood protection to long reaches of the Texas coast. House Document 693, 66th Congress, 2nd Session, and many historical records indicate that before the 19th century the coastal barrier islands had higher and wider dunes than now exist. In recent years, increased habitation of the barrier islands has destroyed much of the vegetation, resulting in erosion and weakening of the dunes. Larger, more stable dunes parallel to the shoreline would provide greater protection from surges and waves produced by tropical storms in the Gulf of Mexico. The experiments involved placing sections of flexible snow fencing to accumulate windblown sand behind the fences, and vegetative planting to stabilize the dunes. A few small low areas of the barrier islands were planted in grass by seeding and sprigging in an effort to establish vege- tative cover and create dunes without the aid of sand fences. Abnormally high tides during October 1965 and May and October 1966 washed channels through some fence-created dunes. The 1966 high tides also seriously damaged most of the planted plots. Hurricane Beulah struck the lower Texas coast on 20 September 1967 and destroyed all the experimental dunes and planting plots near Corpus Christi. 2. EXPERIMENTAL SITES Four locations were selected to conduct the sand dune experiments. They were the southwest end of Galveston Island near San Luis Pass, Packery Channel and Newport Pass on North Padre Island, and Corpus Christi Pass, the intermittent channel generally regarded as the divide between Padre and Mustang Islands. The first site, a small area on the southeast end of Galveston Island near San Luis Pass, was chosen mainly because of its convenience to the Galveston District office. The creation of a practical protective barrier was not considered since neither end of the short test section merged into high ground or existing dunes. Northeast of the San Luis site there are some natural nonuniform dunes. These irregular dunes are relatively low, rising slightly more than 5 feet above natural ground. The test locations on Padre Island were selected to investigate the feasibility of restoring dunes at points where water often passes between the Gulf and the back bay or Laguna Madre during abnormally high tides. Compared to those to the northeast, the dunes on Padre Island are wide and fairly well stabilized, but they are not connected. Padre Island dunes range from 10 to 30 feet in height, and form a substantial bulwark against hurricane surges, except for those low passes where the dunes are disconnected. All of the four test sites are barren portions of the islands where the land slopes gently from the Gulf shoreline to low crests and then down to the bays. The experiments were all made on land ranging from 2 1/2 to 4 1/2 feet above mean sea level. The diurnal range of tide is 1.2 feet at San Luis Pass and 1.7 feet at Aransas Pass near the Padre Island sites. The maximum tidal range is about 2.2 feet at San Luis Pass and about 2.5 feet at Aransas Pass. The four study areas, designated San Luis Pass, Packery Channel, Newport Pass, and Corpus Christi pass, are shown on Figures 1 and 2. Wind diagrams for the Galveston and Corpus Christi areas are shown in Figure 3. Analyses of nine random samples taken at various times from the four study areas showed little or no differences in sand size. Ninety percent of the sampled sand ranged from 0.08 to 0.2 mm in diameter. Small sea shells and shell fragments are mixed with the sand. The fine to very fine sand found on the Texas coast is readily transported by normal winds. During periods of light rain and average wind velocities, sand movement has been observed in the study areas. The diagrams show that the prevail- ing winds are from directions roughly perpendicular to the coastline, which results in movement of the beach sand inland toward the bays. 3. STUDY DESCRIPTION Creating dunes by the use of junk car bodies instead of conventional wood slat fencing was attempted during the earlier stages of the experi- ments. It was reasoned that if the car bodies would trap sand, they might also act as reinforcement to stabilize the newly formed dunes. The car bodies were placed in line parallel to the beaches and for a few weeks appeared to be trapping sand in amounts about equal to that trapped by wood slat fencing. However, after an initial accumulation, the rate of entrapment by the car bodies appeared results were obviously less effective fencing. The ground elevations where were generally lower than those where to diminish rapidly, and the total than those produced by the wooden car bodies were placed originally sand fences were placed. Abnormally high tides caused greater damage to sand accumulations in those lower areas. seemed to be generally greater in the bodies. During normal tide periods, natural deposition of beach materials lower areas occupied by the car Because of this natural accreting action, it is probable that sand accumulated in areas up to 50 feet on either side of the car bodies may not be entirely attributable to those barriers. and 14.) (See Fagunes eS) ls. Car bodies in place are more costly than conventional wood- picket or fabric fencing and apparently trap less sand. Consequently, experiments to build dunes with car bodies have been discontinued by the Galveston District. Wood picket "snow" fencing was used in most of the sand dune experi- ments. 3/8 inch thick, 2 inches wide, 4 feet The fencing consisted of rough cut, square top, yellow pine pickets long and woven with five 2-strand ; i u AMARILLO + \ H = newie|i7ae oe, \ — MEXICO ny { \ — hd ze = See | oaLLas FT tormnes BS ~ j SSE CUB AS ce SAN ANTONIO \ VICTORIA PROJECT IGHRISTL LOCATION VICINITY MAP Bophea ae STALE DF MES PORT .SABEL MEXICO 3000 150 eons BROWNSVILLE ie Approx. Scale: |" Figure 1. Aerial photograph of San Luis Pass, one of four study areas selected to determine the practicability of creating and stabilizing sand dunes. a om ; Z alse ce OXIMATE SCALE 1" Figure 2. Aerial photograph of Packery Channel, Newport Pass, and Corpus Christi Pass, three of the selected study .areas. BEACH ALIGNMENT SAN LUIS PASS AREA GALVESTON, TEXAS BEACH ALIGNMENT PACKERY CHANNEL NEWPORT PASS & CORPUS CHRISTI PASS AREAS 20% CORPUS CHRISTI, TEXAS WIND DIAGRAMS CHARTS SHOW PERCENT OF TIME FROM EACH DIRECTION COMPILED FROM U.S. WEATHER BUREAU RECORDS OF HOURLY PREVAILING VINDSWAT) GALVESTIONG (TEXAS) FOReMHE PERIOD M205) 0 1955 INCLUSIVE AND AT CORPUS CHRISTI. TEXAS FOR THE PERIOD 1905 TO 1948 INCLUSIVE. WIND DIAGRAM LEGEND yO) 1S Rb Pais. < Saesmeam 6a Oe.3 lee Pe Hie) sc) era VRJNL a! SAND MOVING WINDS IN THE STUDY AREAS Figure 3. Wind rose showing sand-moving winds in the four study areas. cables of 13-gage galvanized wire with 1 1/2-inch spaces. All of the picket fencing was erected on nominal 2 by 4-inch wood posts placed 10 feet on center. For the first sections at San Luis Pass, posts 6 feet long were set 2 1/2 feet deep with the remaining 3 1/2 feet above ground and faced so that the 2-inch side would be parallel to the line of fencing for nailing. Subsequent sections in the Corpus Christi area were erected on posts 5 feet long, set 2 feet in the ground, with the 4-inch width faced to receive the fencing. These post settings were more economical and provided a wider, more rigid nailing surface. Extension of the slat fencing 1 foot above the top of the posts had no adverse effect on the stability of the fence. A second tier of fencing was placed on top of the original wood picket fence in the Packery Channel area about 4 months after installa- tion of the initial fence and after the dunes had formed to about 3 1/2 feet above natural ground. The second tier fencing was comprised of about 150 feet of polyethylene plastic material with 5/8-inch mesh and a porosity of 82 percent, about 150 feet of 1/4-inch mesh plastic material with a porosity of 68 percent, and about 100 feet of wooden picket fence for comparison purposes. Soon after installation, portions of the three added sections were blown down or destroyed by vandalism, and no surveys were made to deter- mine comparative sand volume accumulations. Observations did indicate that fabric fence with the lower porosity trapped more sand than fabric with high porosity, and that the wood picket fence trapped more than either of the fabric types. Additional information of the fabric type fencing may be found in a paper by Savage and Woodhouse. (Savage, R. P. and Woodhouse, W. W. Jr., 1968, "Creation and Stabilization of Coastal Barrier Dunes'', a paper published in Proceedings of the llth Conference on Coastal Engineering, ASCE, held in London in 1968.) Table I shows average volumes of sand accumulated by the various fences at the four experimental areas. Locations of the typical sections correspond with the lengths in feet on plans shown on Figures 4 through 14. Although the table reflects average volumes for fence sections of several hundred feet, some smaller sections of about 100 feet in length accumulated up to 16.1 cubic feet of sand per linear foot of fence. 4. VEGETATION Efforts were made to establish grass to accelerate sand accumulation and stabilize parts of new dunes in the San Luis Pass, Packery Channel, and Newport Pass areas. Five 30- by 100-foot and six 40- x 50-foot plots were sprigged or seeded in the San Luis Pass area and seventeen 40- by 100- foot plots were sprigged or seeded in the two areas near Corpus Christi. The planting was done during December 1965 at San Luis Pass and during March 1966 at Packery Channel and Newport Pass. Some plots were sprigged Ss°9 6°Y lot 1S 9°¢ Cae GEG Ors On 9°6 Gals Cal 9°2I Leo) 6°T Lae Geil Gre S‘OT SOG) 0°2 One OS Qual Cecil 0°9 eal S*OT Geo Oak L9 AeW 99 290 99 1eW 9°¢ Oa L°0 LOS ei Pole v'L Sag eal LS 9°¢ Son 99 290 S9 99d s9 das Jo se *yoeoq FO OOF ACOUTT tod paye[nunsoy pues spre, dtqn9 $9 S9 $9 s9 S9 S©) S9 S9 $9 S9 s9 $9 $9 s9 a3eq uoTy adXj, oouad -PT Te ysul Tetztul das das das AON AON AON AON AON AON AON ady ady ady Ae ‘9Q0u9T JO pues Q WOLF YOoF ut 9dueqSTd xx “yoroq JO 100F IeouTT tad spzxek dtqno ut x SeTpog re) SaTpog Ie) sotpog re) aoue4 aoue4 aoued 90ud 4 90ue4 90ud4 a0uaj aouej aud J 90ud 4 JoyoTd 2949Td yoyoTd JOT d JoYOTd JoyYOTd JoYOTd Ja4OTd yeyxOTd yoY9Td SoTpog re) £96 Oss OSS Od Ove 0 0002 OOZLT OOLT 00cT 00cT 008 008 0 008T OO