U eee, ee es. MP 6-75 (AD-AOI2 B32) Establishment of Vegetation for Shoreline Stabilization in Galveston Bay by J. D. Dodd and J. W. Webb MISCELLANEOUS PAPER NO. 6-75 APRIL 1975 Prepared for ; U. S. ARMY, CORPS OF ENGINEERS - ¢8 COASTAL ENGINEERING a RESEARCH CENTER no .6-75 Kingman Building Fort Belvoir, Va. 22060 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 has been made by this Center. Additional copies are available from: National Technical Information Service ATTN: Operations Division 5285 Port Royal Road Springfield, Virginia 22151 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. IMO MBL/WHOI ANE vn UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) z READ INSTRUCTIONS REPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM T. REPORT NUMBER 2. GOVT ACCESSION NO 3. RECIPIENT'S CATALOG NUMBER MP 6-75 4. TITLE (and Subtitle) 5. TYPE OF REPORT & PERIOD COVERED Miscellaneous Paper ESTABLISHMENT OF VEGETATION FOR SHORELINE STABILIZATION IN GALVESTON BAY 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(s) 8. CONTRACT OR GRANT NUMBER(e@ J.D. Dodd J.W. Webb 9. PERFORMING ORGANIZATION NAME AND ADDRESS Texas A&M University Department of Range Science Texas Agricultural esa one Station College Park, Texas 7843 11. CONTROLLING OFFICE NAME AND ADDRESS Department of the Army Coastal Engineering Research Center (CERRE-EC) Kingman Building, Fort Belvoir, Virginia 22060 14. MONITORING AGENCY NAME & ADDRESS(if different from Controlling Office) DACW72-74-C-0002 10. PROGRAM ELEMENT, PROJECT, TASK AREA & WORK UNIT NUMBERS V04230 12. REPORT DATE April 1975 13. NUMBER OF PAGES 67 15. SECURITY CLASS. (of thia report) Unclassified DECL ASSIFICATION/ DOWNGRADING SCHEDULE 15a, 16. DISTRIBUTION STATEMENT (of this Report) Approved for public release, distribution unlimited - DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from Report) - SUPPLEMENTARY NOTES - KEY WORDS (Continue on reverse side if necessary and identify by block number) Marsh Plants Soil Characteristics Shore Stabilization Upper Texas Coast Water Salinity Shore Protection Galveston Bay Transplanting Vegetation Erosion Wave Stilling - ABSTRACT (Continue on reverse side if necesaary and identify by block number) The objective of this study was to determine which resident species of plants adapted to saline conditions can be used to control shore erosion in bays or estuaries. Water salinity and soil physical and chemical characteristics were deter- mined at the experimental planting sites at East Bay near Galveston, Texas. The soil was loam or clay-loam texture and was structurally unstable and subject to _ wave erosion. Soil salinity varied from 2,500 to more than 12,000 parts FORM DD . an 73 1473 EDrtion oF 1 Nov 65 Is OBSOLETE TNCLASSKRIED SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered) 20. Abstract (Continued) | per million and water salinity from below 2,500 to 18,000 parts per million. Twelve plant species were selected for evaluation of their ability to stabilize the shoreline. Giant reed (Arundo donax) is effective in the upper zone (above MHW). Black mangrove (Avicennia germinans) can establish in the middle zone (MLW to MHW) and lower zone (below MLW). Saltgrass (Disttchlis spicata) may be used in the middle zone if wave action is low at planting time. Gulf cordgrass (Spartina spartinae) is adapted for use in the upper zone and smooth cordgrass (Spartina alterniflora) is well adapted for use in the middle and lower zones. Several combinations of species are suggested for different zones. An inexpensive wave-stilling device to protect plantings from wave action is described. 2 UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered) PREFACE This report is published to assist coastal engineers in shoreline stabilization through the establishment and maintenance of vegetation. The techniques for shoreline stabilization with vegetation discussed in this report are applicable to other low-energy estuarine areas. The work was carried out under the coastal ecology research program of the U.S. Army Coastal Engineering Research Center (CERC). The report was prepared by J.D. Dodd, Professor of Range Science, and J.W. Webb, Research Assistant in Range Science, Texas A&M University, under CERC Contract No. DACW72-74-C-0002. Support was also received from the Texas Agricultural Experiment Station, Texas A&M University, College Station, Texas 77843. The authors express appreciation to personnel of the Anahuac National Wildlife Refuge, particularly Mr. Russel Clapper, Manager, for their cooperation; and to W.G. McCully for his advice and encouragement in the initiation of these studies. Special thanks are due A.T. Weichert and B.H. Koerth for their assistance in the field work; and to D.W. Woodard, CERC, for his advice and encouragement throughout the course of this study. Comments on this publication are invited. Approved for publication in accordance with Public Law 166, 79th Congress, approved 31 July 1945, as supplemented by Public Law 172, 88th Congress, approved 7 November 1963. JAMES L. TRAYERS Colonel, Corps of Engineers Commander and Director CONTENTS Page T . ENTRODUGTION sires enuyvcers sree claico\e ok ioi) 6). seal yiyases cen snot lk VSM VE GVOSE Os? Geueby 6 oo ow bbls oc SNS Bs 6 6 o el elo oY 2. PREVIOUS BWOTK isl ge ghel. a lOaairvns: Coy ens co wiper ine AG Cuets avin een, el DESCREPTIONBORMARE AG -wirciarsii-te reminisce ols UnnComne anoun rod em) TITy, PROCEDURES | cia ermuet etme ome ect cits, cals bec viclaitey is Oke) eae Bic an eee Rem Ve, WATER) SATIN 08 Byrceurre lente a lee Sar ai Sich Neiman Oni a, alle geen POI V. SODL CHARAGIERTSIICS IMs. (ost es eet ee eS IESSoD TEXCuRe ee irae ws len wo) Ue, Nouns, ewetiged ten Malt Ma mS) 2, Soul) Selsey? oo 6 Sica) vb ey coo eal ge ome Rined ke a Oo 3. Soil pH and Exeractable Cason rr me imicdmnrube I SS) Vi > VEGETATION ESPABIESHMEN (igre) ayo ce (ia toe ce co lectern nC n= laGene ral mm Pan mrrant tur mer ametewirs Ie en Sy AI 2. Survival and Reproduction a re mR IS ae go oo 4S Bo 2-ZONACLOM!, (asl\) a ieee ie esis) a) Se ai 16), 8 Re ae Se 4. Other Studiesi ic, eupa oe Gus. oy ne ge ee ee ee eS 5. Germination) {eo eee sec. ces) ee een enn see Ol VITO) TIME AND “COST. (olen eens) els) ao a an ee eye a WILD. ¢SUMMARY®! 00.655. 57 seem ESP ooh Sse al hk alte o) one na OL LITERATURE) CITED. cy Rae oo) oe) ay eich da Un ee ge TABLES 1 Climatological data for Galveston Island, located 25 air miles fromestudy. DlOckSi 7) sy te culate mmc onn mee eL 2 List of selected species used in transplant studies MMEBLOCK SL SENTOUCN w WV se ces, ele ety tos retlitade co ine) We ten pee cUamPemeLO 3 A schematic drawing of the design used in each Study: bl ockyae sacs VOM Me, hoe co tence sees or rae 4 Textural analyses of the O- to 2-, 2- to 4-, and 4- to 6-inch depths of the soil in the four study blocks: by “zoner.S (one Meee ae 5 eee ee hee Pe ee 5 Comparison of textural classes between study blocks ... . 29 6 Comparison of texturalclassesmbetween Zone Sima mcnnl-nneZ 10 11 12 13 14 15 16 17 18 19 20 Au Ze, CONTENTS TABLES - Continued Comparison of textural classes by depths . Mean soil salinity, pH and extractable cations by study block, zone and depth . Mean soil salinity, pH and extractable cations by study block, zone and depth . Mean soil salinity at two dates in parts per million by soil depth and zones Mean soil. salinity as parts per million by study block and date . Comparison of soil pH and extractable depth Comparison of soil pH and extractable zones in Blocks I, II, and III . Comparison of soil pH and extractable by depth . Comparison of soil pH and extractable zones in all study blocks cations by cations by cations cations by Comparison by date and soil oon of Se and extractable cations Comparison by date and zone of soil pH and extractable cations Mean percent survival of planted species . Mean number of tillers produced by surviving transplants by species, planting date, Planted species arranged in order of decreasing mean survival percentage within zones . Mean soil Hearts Ee as pote and Block V Soil pH for Block V by depth and zone and zone zone for Page 29 6 SO) o BZ . 34 - 36 . 36 o SY o oy) o oy) - 40 o abl - 44 - 46 - 53 50 SS) 9 OS) 25 24 25 26 Bi 10 CONTENTS TABLES - Continued Mean quantities of extractable cations (yg/gm) in the soil of Block V by depth and zone . Mean percent survival (S), dead (D), and washout (WO) in Block V . Pte Aaekta es os |u/sa seq ed ashen ee Mean percent survival of each species by zone in Block V . Percent seed germination of smooth cordgrass seeds stored dry and in seawater at 6° Celsius . Man-hours required to dig, separate, and transplant 1,000 plants of each species used in five monthly plantings FIGURES Eroding clay shoreline along the north shore of East Bay in Chambers County, Texas . Location of Anahuac National Wildlife Refuge along the shoreline of East Bay oid 6 Location of Blocks I through V and smooth cordgrass (Spartina alterniflora) seed plot on Anahuac National Wildlife Refuge, Chambers County, Texas A general view of Block IV at low tide . A general view of study Block I at low tide A general view of study Block II . A general view of study Block III Three height classes of black mangrove used to determine survival relationships between transplant height and water depth . A temporary wave-stilling device constructed in Block IX . Water salinity in parts per million (ppm) for samples collected ee in See Blocks I oe IV during 1974 p : aN ite: Weld eeeete Page = 0 5 Sy) . 60 . 61 . 63 13 15 16 17 17 18 18 23 23 24 11 12 13 CONTENTS FIGURES - Continued Growth and tiller production of smooth cordgrass in the middle zone, Block IV . A general view of Block V, approximately 4 weeks following mechanical sloping . : A general view of Block V, 7 months after mechanical sloping . Page 5 oul 258 . 58 oe bein, Seat phweig” Wear, ' MAIN TE GMAER « * ‘as . Pt tal ee ee ESTABLISHMENT OF VEGETATION FOR SHORELINE STABILIZATION IN GALVESTON BAY by J. D. Dodd and J. W. Webb I. INTRODUCTION 1. Purpose of Study. Texas has 1,800 miles of bay and gulf shorelines and 2,100 square miles of shallow bays and estuaries. This coastal zone is inhabited by nearly one-third of the population of Texas and nearly one-third the total industry in Texas (Fisher, et al., 1972). Thus, a considerable concern exists for a solution to the shoreline erosion problem in the Texas gulf coast zone. Structural solutions to eroding shorelines are expensive in cost and environmental impact. Use of vegetation to stabilize eroding shore- lines should be less costly and of greater benefit to marine organisms, birds, and the associated environment than structures. Natural estab- lishment of vegetation along the shorelines of Galveston Bay seems to be prevented by wave action. Thus, artificial revegetation is necessary. This study was started to characterize available endemic plant materials and to determine growth requirements for establishment on representative shoreline sediments along the upper Texas coast. The four specific objectives were: (a) to isolate candidate planting materials known or believed to have utility for shoreline stabiliza- tion; (b) to field test candidate planting materials on sites typical of shorelines along the upper Texas coast; (c) to refine present know- ledge on germination requirements, planting technology and stand manage- ment of selected plants; and (d) to compile a preliminary performance estimate equating time requirement and accomplishment for particular operations. 2. Previous Work. Few reports are available on the establishment of vegetation along coastal shorelines. Two reports, Phillips and Eastham (1959) and Sharp and Vaden (1970), describe the sloping and planting of shorelines along tidal rivers in Virginia. These plantings were only partially success- ful. Sharp and Vaden concluded that smooth and salt meadow cordgrasses were the best adapted plants for stabilizing this eroding beach area. Other reports have dealt mainly with stabilization of dredged material and creation of salt marshes. Larimer (1968) reviewed the literature and discussed the possibilities for creating salt marshes in the estuaries of the Atlantic and gulf coasts but did no field work. Chapman (1967) reported on attempts to vegetate a dredged-material island in Galveston Bay with sod, rhizomes, and seeds of Spartina alterntflora. Seed germination was not satisfactory, but transplants did appear to establish and spread. Woodhouse, Seneca, and Broome (1972) examined some of the aspects of reproduction, propagation, establishment, and growth of smooth cordgrass on dredged material in North Carolina. They concluded that establishment on some areas was possible with either seeds or transplants. However, transplants were more adaptable to a wider yariety of conditions. Germination response of Spartina alterniflora to temperature and salinity as well as seedling response to salinity by three height classes was also investigated in North Carolina by Mooring, Cooper, and Seneca (1971). Broome, Woodhouse, and Seneca (1973) reported on the propagation and mineral nutrition required for establishment of Spartina alterniflora. They reported that productivity was probably limited by nutrient supply. Research on establishment of vegetation on dredged material in San Francisco Bay was reported by Mason (1973). He found, based on the physical and chemical characteristics of the dredged material, that it was not a good growth medium for marsh plants. However, the root system of Spartina foltosa converted the anaerobic soil to aerobic soil and survived. Garbisch, Woller, and McCallum (1974) investigated salt marsh establishment and development on shores and dredged materials in the mid- Chesapeake Bay region. They reported no limitations for vegetation establishment above mean high water. Establishment of Spartina alternt- flora in intertidal zones was restricted by wave action and coarse sediment stresses. Similarly to Woodhouse, Seneca, and Broome (1974), they reported increased production by Spartina alterniflora with fertilizer treatments. A review of available information on the establishment of marsh and aquatic plants on newly available sub- strates was compiled by Kadlec and Wentz (1974). II. DESCRIPTION OF AREA The shoreline of Texas consists of both a gulf shoreline and a bay shoreline. The bay shoreline generally lacks sand beaches and in many places is associated with low-lying marshes. Low bluffs exist wherever wave action has eroded the Pleistocene terrace deposits. Estuaries and consequently bay shorelines originated from the drowning of entrenched valleys as the sea level rose in the late Pleistocene age. Some estuaries filled, and deltaic plains formed at mouths of the Rio Grande, Brazos, and Colorado Rivers. A series of barrier islands have formed from the sediment in many areas along the coast. Smaller streams, i.e., the Nueces and San Jacinto Rivers, flow in narrow valleys and empty into bays or estuaries behind these barrier islands (LeBlanc and Hodgson, 1959). Climate differs greatly along the 375-mile Texas gulf coastline. The Galveston area has a relatively high humidity and receives about 40 inches of rain annually (Table 1). Chambers County, immediately "pL6I ‘UOTIeIISTUTWPY ITLOYdsoujy pue ITUeIDQ TeUOTIEN, TeI0L, Zoquisseq IOqua Aon 19q0390 T c zZequeydas 5 9 ysnsny T T Arne T T oun 5 ¢ Ae 0 I Itady T T yorey 0 I Axeniqej I Z Arenuee ee SSS ha ee (eee er | Deen ee ee oo't |os’ Jot: | ATyQuow Teuton aseroay | unututy | unutxey ueUuL 192 B9m9 WOLF sXkeq JO toequnn 9inj redeq vL6T aseIOAY IP9X ZOT vL6I BIOAY LEO COT (soyouy) uotzeIdtdeIg « (2TeyUueryej.) sinjzeroduay, yuo, *syootq Apnj{s wWorzZ SOTIW ATe GZ po.edOT ‘pUeTS] UOJSSATeD IOF CEP [TeITSOTOWWITD “T STGeL north of Galveston has an annual rainfall of 51 inches. In general, a progressively drier climate exists southward until a semiarid condition with less than 25 inches of annual rainfall occurs near the Rio Grande. Since the vegetation and soil types change in a southerly direction this study was confined to the upper Texas gulf coast and more specifically to East Bay in the Galveston-Houston area. Tidal ranges throughout Galveston Bay are generally less than 1.5 feet. Maximum tidal currents, excluding currents in the navigation channels, are about 1 foot per second (Bobb and Boland, 1970). Fisher, et al. (1972) state that "except within the area of significant salt- water wedge and flood-tidal delta deposition, tides are generally unimportant within the bay-estuary-lagoon system, except when amplified by wind." Minimum water salinities in East Bay occur in conjunction with heavy rains, varying distances from Bolivar and San Luis Passes, and the tidal entrances to bays. Water surface salinities in the shallow bay areas are generally about 2 parts per thousand less than bottom salinities at the same locations (Bobb and Boland, 1970). Marine processes have been the chief forces in shaping the shore- line and in forming many of the physiographic features of this region. Some of these features are: Galveston Island, a barrier island sheltering West Bay; Bolivar Peninsula protecting East Bay; Trinity River alluvial valley; Trinity Bay; San Jacinto River alluvial valley; and Galveston Bay. Trinity Bay and Galveston Bay are the seaward continuation of the Trinity and San Jacinto alluvial valleys, respec- tively. These two bays merge to form one of the largest estuaries of the Texas coast. The central part of the bays have a maximum depth of approximately 10 feet with soft mud bottoms. East Bay and West Bay are both shallow, usually less than 6 feet deep, and are 3- to 4- miles wide with soft mud bottoms (LeBlanc and Hodgson, 1959). Shoreline accretion in the bay area has been limited to the im- mediate vicinity of the Trinity and San Jacinto deltas. These deltas are small in comparison to others along the Texas coast due to the small silt loads of the Trinity and San Jacinto Rivers. The dominant process along the bay shoreline has been erosion. The shoreline from April Fool Point to Kemah in Galveston County has been recorded as eroding at the rate of 4 feet annually (U.S. Army, Corps of Engineers, 1954). Sixty miles of shoreline in East Bay, Galveston Bay, and Trinity Bay in Chambers County (Fig. 1) have also eroded at the rate of about 4 feet per year (Carroll, 1974). Fisher, et al. (1972) have compiled an active processes map of the Galveston Bay complex which show areas of active erosion. One of the critical areas is the north shore of East Bay in Chambers County. Two principal wind directions dominate the East Bay area. Persis- tent, southeasterly winds occur from March through November and short “sexey ‘kqun09) sazoqueyj ut Aeg iseqg FO eToys YyILOU OY. BuOTe oUuTTeTOYS AeTS Sutporzg *T oansty 13 lived, but strong northerly winds from December through February (Fisher, et al., 1972). The dominance of winds from the southeast and the winter northers is even more significant when wind duration is multiplied by average hourly velocity. The study area was located on the north side of East Bay along the shoreline of Anahuac National Wildlife Refuge in Chambers County, Texas (Figs. 2 and 3). Blocks I and II have a general southeasterly exposure. The fetch ranges from less than 1 mile in Block I to about 2 miles in Block II. Block III is exposed to the southwest and the fetch exceeds 6 miles. Block VI, located behind the shoreline in a ditch, is pro- tected from both wind and wave action. The only water action results from tidal fluctuations (Fig. 4). Block I has a gentle sloping shoreline with a natural accumulation of shell that exceeds 2 inches in depth in some plots (Fig. 5). In contrast, Block II has a steep-cut bank forming the shoreline (Fig. 6) with the water level always at the base of the bank. Block III has a gentle sloping shoreline, but the surface has been covered by artificial placement of oyster shell to depths of at least 2 inches (Fig. 7). The shoreline, in each block was divided into three zones based on length of inundation. The lower zone was considered to be below mean low tide and was constantly inundated. In contrast, the middle zone consisted of that part of the shoreline between mean low tide and mean high tide. The upper zone was above mean high tide and was inundated only by abnormally high tides. III. PROCEDURES Bay water samples were collected biweekly in each block. Samples were collected approximately 10 feet from shore and stored in airtight bottles until analyzed. Conductivity in micromhos per centimeter for each sample was measured on a wheatstone bridge. Conversion factors listed in U.S. Salinity Laboratory (1954) were used to convert micromhos per centimeter at 25° Celsius to parts per million (ppm). Soil samples were collected on two different dates, 9 February and 24 May 1974 at three locations within each block (end plots and middle plots). An exception was Block IV in which only one location was sampled. At each location, soils were taken at three arbitrary depths, 0 to 2, 2 to 4, and 4’to 6 inches, and in three zones (upper, middle, and lower). Each soil sample was oven dried at 100° Celsius for 24 hours. Shells and rocks were removed and the samples were ground by a mechanical grinder and finally by a mortar and pestle to break up remaining particles. Particles that would not pass through a 2- millimeter screen were removed. Large quantities of shell were re- corded by weight and expressed as a percent of total sample weight. Soil textural analyses followed the procedures outlined by Bouyoucos (1962). Samples were run in duplicate and the average Rterest fe: WHANKAMER ¥ LAE & A . AMANUAC J\\ \, TRINITY GALVESTON BAY (Audubon Bird sonensery // VINGT-ET-UN ILANOS 4 CHAMBERS COUNTY TEXAS SCALE m WES 4 ALBUQUERQUE NEW ME KICD— MARC HS 1969 Figure 2. Location of Anahuac National Wildlife Refuge along the shoreline of East Bay (From U.S. Department of Interior). Ss ip oO ONG SHOP AND STORAGE AREA ° va 1/2 1 "SCALE iN MILES N LEGEND === REFUGE BOUNDARY =—— SHELLED ROADS GGS GOOSE GRAVEL STATION === DIRT ROADS Figure 3. Location of Blocks I through V and smooth cordgrass (Spartina alterntflora) seed plot on Anahuac National Wildlife Refuge, Chambers County, Texas. A general view of Block IV at low tide. Smooth cordgrass in foreground was planted 18 January 1974. Photo taken 22 February 1974. Figure 5. A general view of study Block I at low tide. Note the occurrence of natural shell on the soil surface. Smooth cordgrass in foreground was planted 20 May 1974. Photo taken 20 September 1974. \7 Figure 6. A general view of study Block II. Note the sharp bank forming the shoreline. Plants in foreground are smooth cordgrass, transplanted in July 1974. Photo taken in September 1974. Figure 7. A general view of study Block III. The occur- rence and accumulation of artificially placed shell in this study block is shown in the fore- ground. Note the establishment, growth, and seed stalk production of giant reed (Arundo donax) above mean high tide. Planting was made on 9 January 1974. photo taken 23 November 1974. percent sand, silt, and clay was calculated. Textural classification was accomplished utilizing the textural triangle diagrammed by Jacobs, etal Goze Soil salinity for each sample was determined by electrical con- ductivity of the saturation extract. Sample preparation and collection of extracts followed the procedures outlined in U.S. Salinity Laboratory (1954). However, only 100 grams of soil were used for the saturated paste. The pH (hydrogen-ion concentration) of each extract was deter- mined on a pH meter. Four selected extractable cations were measured in the extract. Calcium, (Ca), potassium (K), and sodium (Na) were measured by flame spectrophotometry and magnesium (Mg) by atomic absorption. Due to high concentrations it was necessary to dilute aliquots of the extract. Data in parts per million were converted to micrograms per gram (ug/gm) of soil. Twelve plant species were selected for trial transplants as shoreline stabilizers (Table 2). A randomized complete block design was used with four blocks. Each study block was subdivided into 12 plots (Table 3), 1 for each species, and subsequently divided into 5 subplots. Subplots were planted on five different dates, 9-18 January, 1-2 March, 10-13 April, 20-24 May, and 8-10 July 1974. Subplots were further divided into three tidal zones (upper, middle, lower). Each subplot was divided in eight rows, at 3-foot intervals, ex- tending through the zones. Within rows the transplants were at 2-foot intervals and the number of transplants in each row was recorded. The transplant material was culms, stems, or rhizomes, and associated roots, except for saltcedar (Tamartx gallica) (cut stems). Winter plantings were primarily rhizomes and root systems and the spring and summer plantings utilized current green growth for each species. Tall plants, such as giant reed (Arundo donax), common reed (Phragmites communis), and big cordgrass (Spartina cynosurotdes) were pruned to heights of 16 to 30 inches. Transplant material was dug, separated, and planted by hand. Man-hours to dig, separate, and plant were recorded for each species. Block V was established 15-16 March 1974 to further delimit the zonation of plants and to explore the possibility of mechanical sloping before revegetation. A bulldozer was used to develop an ap- proximate 10:1 slope on 200 feet of land at the shoreline. Three areas were established in this block with 13 plots each. Each plot consisted of a row for each study species. In addition, upper, middle, and lower zones were defined. In Blocks I through V three separate evaluations of plantings were made. The first was on 10-18 June, prior to completion of all plantings. On 19-20 September, a fall evaluation was made. The winter evaluation was on 21-22 November 1974. Plants were recorded as alive if green, dead if present, but brown and absent if the Table 2. List of selected species used in transplant studies in Blocks I through IV, Common name ocientific name if Giant reed Arundo donax Black mangrove Avicemnta germtnans Avtcennta ntttda Seashore saltgrass, | Dtstichlis spicata D. spteata var, spicata saltgrass Needlegrass Juncus roemertanus Common reed Phragmttes communis Phragmites australis American bulrush Setrpus americanus Olney bulrush Setrpus olneyt Setprus chilensis Saltmarsh bulrush Setrpus robustus Setrpus marttimus Smooth cordgrass Spartina alterntflora| S. alterniflora var. glabra Big cordgrass Spartina cynosurotdes Gulf cordgrass Spartina spartinae sacahuista Saltcedar Tamarix galltca transplant could not be located. The number of tillers per surviving transplant, tiller height, and height of the original transplant was determined. Height classes were separated at 10 centimeter intervals with plants above 100 centimeters placed in class 11. Percent survival and percent absent were derived by dividing green or absent by the total number planted. The average number of tillers was derived by dividing number of tillers by number of green transplants. Smooth cordgrass (Spartina alterniflora) seeds collected by hand on two different dates (10 November and 1 December) in the fall of 1973 were used to determine storage procedures and germination methods. All seeds were stored at 6° Celsius for at least 6 weeks before germination tests. Some seeds were stored dry while others were stored in seawater containing 8,000 ppm salinity (Mooring, Cooper, and Seneca, 1971). All seeds were checked for the presence of caryopsis within glumes before germination tests were conducted. Petri dish tops with filter paper were sterilized in an autoclave. One hundred seeds of a test type were placed in each petri dish and sealed with saran wrap and with a rubberband. 20 SLOId AHL JO AQIS AVA SN RS —_—_ =~ NS ~~ ~_oC CSE NOES ~~~ NN Se o_O oC ~~ eR SR Re =—o_OoC —_™ @T A°ld «=o, «30TH =«=sOT:s«9Td 6 39Td 8 3°Td £ td 9 2°Td G 3°Td 9 30Td € 3°Td Z 3°Td ‘aousubes Butquerd ouo a2eLysN{ [Tt sysew ysej| "30Tdqns yove 0} paustsse A[Wopuez sem ojep 3utque{d pue od e 02 paustsse ATwOpueL sem Ssatoads yoeq °szoTdqns gs oUT paprAtTpqns soyIAInzZ sem yoTd yoee pue sjotd 7Z[ Jo peystsuod yOoTq yoeg *ydoTq Apnis yoee UT pesn usTSOp ay JO BUTMeIP ITJeUIDYIS Vy T id “¢ 9TqeL 2| Petri dishes were then placed on a metal tray and covered with black plastic to ensure darkness. All seeds were germinated in the dark with alternating thermal periods of 20° Celsius (16 hours) and 30° Celsius (8 hours) in a consol germinator (Mooring, Cooper, and Seneca, 1971). The following variables were tested: (a) dry seeds in glumes collected 10 November 1973, (b) wet seeds in glumes collected 10 November 1973, (c) dry caryopses (no glumes) collected 10 November 1973, (d) wet seeds in glumes collected 1 December 1973, and (e) wet seeds with gibberellic acid collected 10 November 1973. A total of 33 soil samples (11 at each location) were collected 20 June 1974 at the shoreline, 50 and 150 feet from the shore. These samples were placed in plastic bags for transport to the laboratory. The soil was spread on shallow trays and observations for seed germina- tion were made for 3 weeks. Soil was moistened as necessary with distilled water. Four soil samples from the upper and middle zones and three samples from the lower zone were collected in July 1974 and placed in shallow pans. Twenty-five seeds of smooth cordgrass were placed in each sample and the soil was moistened with seawater as necessary. Seed germination was recorded for a 3-week period. Smooth cordgrass seeds were planted 23 March 1974 in a 10- by 12- foot plot in a wave-protected area. Seeds were mixed with substrate by hand. An experiment to compare survival of different transplant heights (4 to 15, 16 to 30, and over 30 inches) for black mangrove (Avicennia germinans) was planted 17 October 1974 (Fig. 8). Three replications (Blocks VI, VII, and VIII) were established. Blocks were designed to allow two additional monthly plantings of each height classes. Block IX was designed to test the establishment and growth of plants when protected from wave action. A temporary wave-stilling device (Fig. 9) was constructed from baled hay, wire net, steel cable, and pipe. The maximum height of the device was about 36 inches. Twelve rows of black mangrove, saltgrass (Dtsttchlts spicata), needlegrass (Juneus roemertanus), common reed, smooth cordgrass, and big cordgrass were planted behind the wave-stilling device. IV. WATER SALINITY Water salinity was variable at all study locations during 1974 (Fig. 10). Salinity at Block I was affected by influxes of freshwater from Oyster Bayou. Thus, the biweekly salinity values at this location were generally lower than for the others. An exception occurred in July, a period of low precipitation, when salinity was about 15,700 ppm. Lowest values were during the winter and following a heavy pre- cipitation period in May. Salinity then was generally below 2,500 ppm. 22 Figure 8. Three height classes of black mangrove used to determine survival relationships between transplant height and water depth. Transplant heights ranged from over 30 inches (left) to 16 to 30 inches (center) to 4 to 15 inches (right). Figure 9. A temporary wave-stilling device constructed in Block IX. The device is constructed of pipe, wire netting, cable, and baled hay. 23 RAINFALL IN INCHES *potazed owes oyy IO} UMOYS OST ST [TejJuTeYyY “VL6T SUTINp AT ysnorzyi J syoorg Apnys ut ATYSOMTG pazdeTTOO sotdwes ztoz (wdd) uott{rtwm sod szaed ut A}TUTTeS 101eN 31Vv0 ‘29g «= ‘AON 490 ‘ydag -bny Aine = =aune) = =Kkow udy JOW ‘gal “OT eansty ‘uor 0002 Co00F SESS 32 O;g 0009 ALINIWS Wdd Wi 24 Salinities at Block II were similar to Block I during the fall-winter period (Fig. 10). However, during periods of low precipitation (April and October) salinity values were high, with the maximum of 18,500 ppm recorded in mid-October. Water salinity at the mechanically shaped Block V was similar in magnitude and trends to Block II. Water samples from Blocks III and IV fluctuated widely throughout the year, but were similar in magnitude at most sampling intervals (Fig. 10). The major differences occurred in winter with water from Block IV higher in salinity than Block III. In late August, during a period of relatively high precipitation, water salinity in Block III increased, while in Block IV a decrease was recorded. Water salinities fluctuated throughout the year irrespective of location, but mirrored the precipitation. In general, the lowest readings were in Block I, while the highest occurred as distance from Oyster Bayou increased. This resulted in three distinct periods of low salinity: winter 1973, early summer 1974, and fall 1974. In contrast, two periods of high salinity occurred. The first, of rela- tively low magnitude, was from mid-February to mid-May and the second, of higher magnitude was from June to November. Periods of low water salinity should be favorable for the establishment of transplants while the high summer salinity period should be considered as a poor period for establishment. The amount of precipitation received was an indica- tor of water salinity levels within East Bay. V. SOIL CHARACTERISTICS 1. Soil Texture. The shoreline on East Bay has been commonly referred to as clay. However, textural analyses of the soil in each block and in 3 zones (upper, middle, and lower) and at various depths to 6 inches indicated the soil was generally of a loam or clay loam texture (Table 4). The surface 2 inches of the upper zone, Block II; lower zone, Block III; and lower zone, Block IV were either sandy loam or sandy clay loam in texture. In general, the clay loam texture occurred at depths greater than 2 inches. Thus, the general sequence of soil texture was a surface layer (0 to 2 inches) of loam underlain by a layer (2 to 6 inches) of clay loam. In most blocks the percent sand exceeded that of other particle classes and clay particles occurred in the smallest quantities. These textural properties result in a highly erodible soil, probably due to an unstable structure. The result of this unstable structure is a soil substrate that readily erodes with any form of disturbance. Thus, the continual wave action results in sloughing of the shoreline and a high annual loss. In addition, the disturbance associated with planting causes an unstable condition and again the continual wave action disperses the soil from around the planted material and ultimately the materials are washed out. 25 Table 4. Textural analyses of the O-to 25 2-to 4 and 4-to 6-inch depths of the soil in the four study blocks by zone (U - upper, M - middle, L - lower). Data based on the mean of three samples. Depth Percent eae ee Block | Zone Inches Sand ea | ciay | Texture eae) GRE a Re Sel Pee ee eee Loam Loam Loam Loam 0 to 2 46.6 Clay Loam Clay Loam Loam Clay Loam Clay Loam Sandy Loam Clay Loam Clay Loam Clay Loam II M Clay Loam Clay Loam to 50.6 5 5 Loam L 2 to 4 45.9 SZ 21.8 Loam 4 to 6 45.0 31.6 255 Loam Table 4. Textural analyses of the 0-to 25 2-to 45 and 4-to 6-inch depths of the soil in the four study blocks by zone (U - upper, M - middle, L - lower). Data based on the mean of three samples-Continued. Eo Percent | Percent Zone (Inches) Sand Silt Clay. a ae a) a Lee] = lesan ea [cri 0 to 2 45.3 24.4 2 to 4 35.3 35.3 4 to 6 34.0 38.5 0 to 2 36.8 36.6 2 to 4 Oo 42.4 4 to 6 34.6 36.4 0 to 2 62.8 US 2 to 4 46.3 32.8 4 to 6 45.3 30.2 0 to 2 31.6 37.1 2 to 4 28.8 40.6 4 to 6 23.5 37.3 Texture Clay Loam Clay Loam Clay Loam Sandy Loam Loam Loam Sandy Clay Loam Clay Loam Clay Loam 27 Soil texture and the resulting unstable structural condition is a greater problem to shoreline stabilization than establishment of plant material. Any form of barrier that will reduce the wave action and its resultant dispersion of the soil will enhance vegetation establishment and stabilization of the eroding shoreline. In comparing soil texture by blocks, disregarding both depth and zone, Blocks I, II, and III were classed as loam soils (Table 5). In contrast, Block IV, in the drainage ditch, was classed as a clay loam soil. Overall, the soils of Blocks I, II, and III were very similar with only minute differences in quantities of each particle class. In comparing the soil in Block IV to the other three, the percent contri- buted by the sand particles decreased while the clay significantly increased. A change occurred in soil texture between zones of Blocks I, II, and III (Table 6). The upper, relatively undisturbed zone was of a loam texture to a depth of 6 inches and similar to the inundated lower zone. In contrast, the middle zone, had a significantly higher pro- portion of clay and a significantly lower proportion of sand resulting in a clay loam texture. This zone is exposed to more wave action than the others. As a result the surface soil has been removed. The O- to 2-inch depth contained significantly more sand in Blocks I, II, and III than either the 2- to 4- or the 4- to 6-inch depths (Table 7). This higher sand content was accompanied by a significantly lower clay content in the surface soil. The percent sand varied only slightly in the 2 to 4 and 4 to 6-inch depths, but was higher than either silt or clay. Silt content was similar at all depths and con- tributed about 33 percent of the soil particles. 2. Soil Salinity. Soil samples for the determination of soil salinity were collected in February and May 1974 (Tables 8 and 9). Two collection dates provided data for comparison over time and under varying water salinity conditions and precipitation. Mean soil salinity in February ranged from over 11,000 ppm in the 4- to 6-inch depth of the upper zone to less than 2,600 ppm in the 4- to 6-inch depth of the lower zone (Table 10). The trend was decreasing soil salinity from the upper to the lower zones. In the upper zone, salinity in the surface 4 inches of soil was similar with an increase in the 4- to 6-inch layer. However, in the middle and lower zones, salinity varied only slightly with a change in depth. Water salinity at this time ranged from 1,100 to 3,200 ppm between blocks, indicating soil salinity was higher than water salinity. In May following the relatively dry month of April, soil salinity values were higher than in February (Table 10). The lowest salinity, over 8,000 ppm, was in the 2- to 4-inch depth of the lower zone. While the highest, over 12,000 ppm, was in the O- to 2-inch depth of the upper 28 Table 5. Comparison of textural classes between study blocks. Percent Percent Percent Sand Silt Clay Texture Se en Ene eee OT RS eS *Means followed by the same letter are not significantly different at the 95 percent level. Table 6. Comparison of textural classes between zones (Upper, Middle, Lower). Data combined for Blocks I, II, and III. Percent Percent Percent Sand Saale: Clay [La ae pe] Lm SO Se] Texture Upper Loam Middle Clay Loam Loam *Means followed by the same letter are not significantly different at the 95 percent level. Table 7. Comparison of textural classes by depths (0 to 2, 2 to 4, 4 to 6 inches). Data from Blocks I, II, and III have been combined. Depth Percent Percent Percent (Inches) Sand Saute Cla Texture eer el ee A 0 to 2 Loam 2 to 4 Loam Clay Loam *Means followed by the same letter are not significantly dif- ferent at the 95 percent level. 29 Table 8. Mean soil salinity, pH and extractable cations by study blocks, zone (U - upper, M - middle, L - lower) and depth. Samples collected 9 February 1974. Data based on a mean value of three samples in Blocks I, II, and III and two samples in Block IV. Extractable Cations Depth Salinity (microgram per gram) Blocks | Zones | (Inches) (ppm) pH Na Bae Sal F 7Q Ts We ZorO) Nar Si/eenlen alates 1,234. 6.9 | 68.2 | 38.0] 264.0 | 1,452. Go8 || 2560 |) Silo |) Ooo 778 Uh 16.9 | 46.4] 83.1 773 Gok 16.7 | 43.7 | 96.6 893 Hats) UME S56) SISOS) | Zhai. Oo |) AVS SilsO | 47/odk 892. 6.8 | 19.0 | 32.6] 140.9 | 1,014. FoS \) BOS |) Zc | 4s) 348. 30 Table 8. Mean soil salinity, pH and extractable cations by study blocks, zone (U - upper, M - middle, L - lower) and depth. Samples collected 9 February 1974. Data based on a mean value of three samples in Blocks I, II, and III and two samples in Block IV-Continued. Depth Zones (Inches) exeeene ane al 0 to 2 U 2 to 4 4 to 6 0 to 2 M 2 to 4 4 to 6 0 to 2 L 2 to 4 4 to 6 0 to 2 U 2 to 4 4 to 6 0 to 2 M 2 to 4 VAP tor 6 0 to 2 L* 2 to 4 4 to 6 Extractable Cations (microgram per gram) Blocks | pS BSS BSS W & Ww [oe} dS ito) ON i