Maintenance Material and Bird Island Restoration at Sundown/Chester Island, Matagorda Bay, Texas

Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

MAINTENANCE MATERIAL AND BIRD ISLAND RESTORATION AT SUNDOWN/CHESTER ISLAND, MATAGORDA BAY, TEXAS

Cris Weber1, Dave Buzan2, Tom Dixon3, Iliana Peña4, Tim Wilkinson5

ABSTRACT Sundown Island is located on the mid-coast of Texas (Matagorda Bay), approximately 1.3 miles west of the Matagorda Peninsula, north of the Matagorda Ship Channel (MSC), and southeast of the Gulf Intracoastal Waterway (GIWW). The island has been an official Audubon Texas bird sanctuary since 1973, was formed in 1962, and has played a significant role in brown pelican population recovery (starting with 2 pairs in 1987 to over 3,300 pairs in 2014). With intensive efforts to build partnerships with local, state, and federal stakeholders, it was possible to assemble a Task Force that collaborated on potential erosion mitigation, shoreline stabilization, and restoration alternatives for Sundown Island. The northern end of the island was the highest priority, where an existing concrete mat revetment was failing and exacerbating erosive forces along this shoreline section. Historically, the island received dredge material every 12-16 months which maintained this important colonial water bird rookery. However in 2007, Sundown Island lost one source of beneficial material when the GIWW was realigned and moved 2 miles further north. Ship-induced wakes and currents from the MSC reduced the island from 40.5 hectare (100 acres) to its present size of approximately 26 hectare (65 acres). Maintenance dredging has become less frequent, reducing the availability of material available for beach renourishment. During most recent dredge maintenance cycles in 2014, over 90,000 cubic meters, cu m, (119,000 cubic yards, cy) of maintenance material from the MSC were placed at this priority area. With 1.22 hectare (3 acres) of material available post-placement, this provided additional nesting and foraging habitat for important avian species. Beneficial use of dredge material from the MSC provided a critical stop-gap placement effort necessary to mitigate continuous sediment loss from this valuable colonial nesting site.

Keywords: Dredging, beneficial use, dredged material, avian conservation, erosional hotspot management. INTRODUCTION Sundown Island Sanctuary (Figure 1), also locally known as Chester Island, is a low-lying, 28 hectare (70 acres) island originally built from dredge spoil in 1962. It is located near where the Matagorda Ship Channel and the Gulf Intracoastal Waterway cross in Matagorda Bay, east of Port O'Connor and southeast of Port Lavaca, in the Texas coastal bend. The island is leased from the General Land Office and managed by the National Audubon Society's Texas Coastal Sanctuaries program, as part of the Society's 15,261 hectares (3,000 acre) network of 33 islands that stretch from Mexico to Louisiana. Beneficial use of material, within free-haul distances of maintenance dredging projects, is a critical component of coastal restoration and shoreline erosion protection. Similarly, proper management and conservation planning of important colonial water bird rookeries and nesting sites are critical components of avian conservation.

1Coastal Engineer, Freese and Nichols, Inc., 14431 Morado Circle, Suite 300, Austin, TX 78759. T: 512-617-3134, Fax: 512- 617-3101, Email: [email protected]. 2Coastal Scientist, Freese and Nichols, Inc., 14431 Morado Circle, Suite 300, Austin, TX 78759. T: 512-617-3134, Fax: 512-617- 3101, Email: [email protected]. 3 Avian Ecologist, Freese and Nichols, Inc., 14431 Morado Circle, Suite 300, Austin, TX 78759. T: 512-617-3134, Fax: 512-617- 3101, Email: [email protected]. 4 Director of Conservation, Audubon Texas, National Audubon Society, 2201 Main Street, Suite 600, Dallas, TX, 75201 T: 210- 913-9798, [email protected]. 5 Sundown/Chester Island Warden, Sundown Island Sanctuary, National Audubon Society, P.O. Box 373, Port O’Connor, TX, 77982, T: 281-844-0716, [email protected].

208 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

Figure 1. Sundown Island location (NAAIP, ESRI, Gooogle Earth).

Local Residents The island hosts substantial numbers of nesting Brown Pelicans (Pelecanus occidentalis), Gull-billed Terns (Gelochelidon nilotica), Royal Terns (Thalasseus maximus), Sandwich Tern (Thalasseus sandvicensis), Black Skimmers (Rynchops niger), and other birds. In 2014, Sundown hosted 16,070 breeding pairs (Wilkinson, 2014), representing 18 species, including many of conservation concern (e.g., Royal Tern, Sandwich Tern, Black Skimmers, Reddish Egrets [Egretta rufescens], and Rosette Spoonbills [Platalea ajaja]). Sundown was identified as one of 15 priority nesting sites for the Reddish Egret by the Gulf Coast Joint Venture (Vermillion and Wilson, 2009). Table 1. Bird species that utilize Sundown Islaand (from Audubon Texas). BREEDING BIRDS PART TIME RESIDENTS (Partial List)

Brown Pelican American White Pelican (w)

Great Blue Heron Magnificent Friigatebird (s) Great Egret Double-crested Cormorant (w)

Snowy Egret American Wigeon (w) Little Blue Heron Mottled Duck (w)

Tricolored Heron Blue-winged Teal (w)

Reddish Egret Northern Shoveler (w) Cattle Egret Green-winged Teal (w) Black-crowned Night-Heron Redhead (w)

White Ibis Lesser Scaauup (w) Glossy Ibis (occasionally) Black-bellied Plover (w) White-faced Ibis American Avocet (w)

Roseate Spoonbill Ruddy Turnstone (w) American Oystercatcher (occasionally) Sanderling (w)

Laughing Gull Ring-billed Gull (w) Gull-billed Tern Herring Gull (w)

Royal Tern Forster's Tern (w) Sandwich Tern Horned Lark (w) Black Skimmer Yellow-rumped WWarbler (w) Red-winged Blackbird Common Yellowthroat (w) Black-bellied Whistling Duck Savannah Sparrow (w) (w = winter, s = summer)

Existing Structures Several shoreline stabilization structures have been implemented at the island for sediment control, including geotextile tubes (geotubes) and an articulated concrete mat revetmment, which have resulted in a range of outcomes (Fig. 2). The southwestern end of the island was stabilized with a series of geotubes arranged similar to a groin field, and the northeastern end of the island was stabilized with a combination of geotextile tubes and an articulated concrete mat revetment.

209 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

Figure 2. Shoreline stabilization structures at Sundown Island (NAIP, ESRI, Google Earth).

The geotubes installed at the southern end of the island delivered a positive outcome, providing stability for dredge material placed at this location. Although the erosional processes remain active, the general configuration has remained consistent. In contrast, the northern end of the island has experienced accelerated erosion due to the failure of the revetment. The revetment is stranded roughly 30 meters offshore of the shoreline, which now acts to focus wave energy along between the structure and the shoreline. Additionally, the unraveling of the revetment from north to south has exposed the northern reach of the USACE geotubes to intensive wave energy resulting in catastrophic failure of roughly 50 meters of structure with imminent failure of the remaining structural integrity and unraveling of the island shoreline. Recent Dredge Material Placement The origins of Sundown Island (and subsequent maintenance) are entirely from beneficial use of dredge material placement from the GIWW and the MSC. Due to tightened funding and competing priority projects over the past several years, the ability to use dredge material beneficially on the island has become less consistent. An evaluation of the placement projects conducted by the USACE to maintain the MSC from 2009 to 2014 indicated the following (Audubon Texas, 2015): • In 2009, 112,390 cu m (147,000 cy) of dredged material were designated for placement at Sundown Island. • In 2014, the USACE placed 90,000 cu m (119,000 cy) of dredged material on Sundown Island. • The total available material from the MSC was estimated to be over 1.2M cu m (14.6M cy), with only a small fraction going to Sundown Island.

210 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

Table 2. Dredge maintenance material assessment for Sundown Island (Audubon Texas, 2015). Designated for Sundown Island Total MSC Quantity Quantity Available Project Year Available Cu M (CY) From STA To STA (CY) 2009 3.61M (4.7M) 8+000 15+000 112,390 (147,000) 2011 1.99M (2.6M) N/A N/A 0 2012 3.11M (4.1M) N/A N/A 0 2014 2.53M (3.3M) 6+800 15+000 90,980 (119,000) 2009–2014 Available in MSC 2009–2014 Designated for Sundown: 11,232,400 cu m (14,691,476 cy) 203,400 cu m (266,000 cy)

During the same time period from the beginning of 2009 to 2014, the total estimated island area has eroded from roughly 30 hectare (75 acres) to less than 26 hectare (64 acres), a loss of almost 15 percent over 5 years. In the absence of sustained funding for advanced shoreline protection solutions, the dredge maintenance material is the only available solution for mitigating ongoing erosional forces along Sundown Island’s shoreline. 2014 PLACEMENT OPERATIONS The USACE provided roughly 203,400 cu m (119,000 cy) of sediment from the MSC dredge maintenance operations over a three week period in late 2014. Figure 3 indicates the USACE alignment stationing designations for the MSC used for placement along the northern end of Sundown Island.

Figure 3. Timeline of 2014 placement operations at Sundown Isand.

The dredging of the MSC and placement operations were conducted by Orion Construction. The Audubon Texas warden for Sundown Island and Director of Conservation (Tim Wilkinson and Iliana Pena, respectively), and Freese and Nichols senior scientist, Dave Buzan observed placement of sediment at the critically eroding hot-spot along the northern and western shoreline. The contractor field crews and island managers coordinated efforts to optimize placement of the incremental volume available from this dredge maintenance cycle.

211 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

Critical Erosional Hotspots The predominant wave energy is generated from winds approaching form the south, but although they have a lower frequency of occurrence, the long fetch (roughly 12 miles to the north and 25 miles to the northeast) creates high- intensity, episodic waves impacting the island from the north and northeast. The articulated concrete mat (ARM) revetment was installed along this northern shoreline and wraps around the northern shoreline from the northwestern extent, down to the middle of the southern shoreline. Unfortunately, due to funding constraints, the northwestern end of the revetment was never properly established, such that the wave energy approaching from the northerly direction impacts parallel to the revetment crest, which subsequently initiated an unravelling the revetment and created an extremely unstable erosional hotspot that focuses wave forces along the leeward side of the structure. Figures 4 shows the northern leg of the derelict ARM looking north along the northern shoreline during a low-tide event in early 2014, and Figure 5 indicates the leeward erosion and overtopping at the 90-degree bend prior to placement operations.

Figure 5. Derelict articulated concrete mat, facing North.

Figure 4. Bend of derelict articulated concrete mat, facing NW.

212 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

As discussed previously, the dredge maintenance cycle targeted the critically eroded shoreline landward of the revetment. The vast majority of the material was placed between the 90-degree bend of the structure moving towards the northern shoreline. Figure 6 shows the general placement operations, and Figure 7 indicates that the erosional embayment behind the revetment at the elbow is completely filled to the crest of the revetment.

Figure 6. Placement operations along the Northern shoreline.

After placement behind the revetment along the northern shoreline, the remaining material was placed along the northwestern shoreline moving from northeast to southwest, although, the erosion along this section remains rather extreme, with high vertical scarps and exposed geotextile tubes, resulting in the low-density placement providing an incremental increase in volume in a thin strip of material placed in front of geotubes.

Figure 7. Dredge Material at crest elevation of revetment facing NW.

213 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

CONCLUSIONS Historically, Sundown Island received dredge material every 12-16 months which helped maintain this important colonial water bird rookery. With the loss of one primary source of supplemental dredge material from the GIWW realignment and much less frequent maintenance dredge cycles for sediment available from the MSC, there is much less renourishment material available to withstand the ongoing shoreline erosion. Continuous ship-wakes from passing ships in the nearby Matagorda Ship Channel (MSC), operational and storm currents and waves, and unmaintained structures along the shoreline are contributing to extreme background and localized erosion processes removing sediment from the island’s shoreline. The recent beach nourishment operations at Sundown Island addressed a critical stop-gap measure necessary for shoreline protection, but the available material provided only an incremental volume increase. Therefore, the primary recommended shoreline protection alternative is a directed beach nourishment program to address critically eroding hotspots using maintenance material as it becomes available. This effort requires coordination with USACE dredge operations for upcoming projects and USACE planning to provide a consistent sediment source for placement operations; implementing a Memorandum of Understanding between USACE, Texas Audubon, and the necessary state and federal agencies would further ensure continued beach nourishment from channel maintenance events, and would streamline USACE coordination efforts. The secondary recommendation for shoreline protection is a beach nourishment program with structures focusing on high priority areas (based on background and active erosion patterns, erosional hotspots, etc.) identified around the island shoreline, specifically focusing on structures that attenuate wave energy and provide control of both longshore and cross-shore sediment transport. Implementation of a re-nourishment program in coordination with sediment retention and wave attenuation structures is the optimal scenario for meeting Audubon’s project objectives: 1) restore historical area of the island, and 2) protect island shoreline from existing erosional forces. REFERENCES Audubon Texas, Bird Census data. http://www.sundownisland.org/ (retrieved August 13, 2014). Audubon Texas (2015). “Sundown Island Shoreline Protection and Restoration Project,” Conceptual Design Alternative Analysis Report. Golder, W., D. Allen, S. C., and Wilder, T. (2008). “Dredged material as a tool for management of tern and skimmer nesting habitat," ERDC TN-DOER-E24, U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi. http://el.erdc.usace.army.mil/dots/doer/doer.html Hanson, H., and Kraus, N. C. (2001). “Chronic Beach Erosion Adjacent to Inlets and Remediation by Composite (T- Head) Groins,” ERDC/CHL CHETN-IV-36, U.S. Army Engineering Research and Development Center/Coastal and Hydraulics Laboratory, Vicksburg, Mississippi. Kraus, N. C, Galgano, F. A. (2001). “Beach Erosional Hot Spots: Types, Causes, and Solutions,” ERDC/CHL CHETN-II-44, U.S. Army Engineering Research and Development Center/Coastal and Hydraulics Laboratory, Vicksburg, Mississippi. Leberg, P.L., Deshotels, P., Pius, S., and Carloss, M. (1995). “Nest sites of seabirds on dredge islands in coastal Louisiana”, Proceedings of the Southeastern Association of Fish and Wildlife Agencies, 49, 356–366. Mallach, T.J. and Leberg, P.L. (1999). “Use of dredged material substrates by nesting terns and black skimmers”, Journal of Wildlife Management, 63(1):137–146. Stucker, J.H., Buhl, D. A., and Sherry, M. H. (2013). “Consequences of Least Tern (Sternula antillarum) microhabitat nest-site selection on natural and mechanically constructed sandbars in the Missouri River”, The Auk 130(4):753–763. Texas Coastal Observation Network (TCOON). Port O’Conner Station 057. http://www.cbi.tamucc.edu/obs/057 (retrieved January 15, 2015). Texas Parks and Wildlife Department (TPWD). (2006). “Attracting interior least terns to enhanced nesting habitat on a reservoir in NE Texas”, Grant No. E-54. 27 pp. Thompson, B.C., and Slack, D. R. (1982). “Physical aspects of colony selection by least terns on the Texas coast. Colonial Waterbirds”, 5:161–168. U.S. Army Corps of Engineers. (2014). Historical Matagorda Ship Channel Dredging Bid Schedules (2009 to 2014). U.S. Army Corps of Engineers, Galveston District. Retrieved August 6, 2014 Vermillion, W.G., and Wilson, B.C. (2009). “Gulf Coast Joint Venture Conservation Planning for Reddish Egret,” Gulf Coast Joint Venture, Lafayette, Louisiana. 18pp.

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Weber, C. K. (2000). “Evaluation determination of erosional hot spots after beach fill placement in Longboat Key, Florida,” UFL/COEL-2000/008, Coastal and Oceanographic Engineering Program, University of Florida, Gainesville, FL, 108 pp. Wilkinson, T. (2014). 2014 Annual Bird Census. http://www.sundownisland.org/ (retrieved August 13, 2014). CITATION Weber, C.K., Buzan, D., Dixon, T.D., Peña, I., Wilkinson, T. “Maintenance Material and Bird Island Restoration at Sundown/Chester Island, Matagorda Bay, Texas,” Proceedings of the Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015", Houston, Texas, USA, June 22-25, 2015.

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