APPENDIX B ECOSYSTEM RESTORATION INTRODUCTION In 2007 an Existing Conditions Report (ECR)/Feasibility Study titled, “Chacon Creek, Laredo, Texas, Draft Feasibility Report and Environmental Assessment” was produced to assess challenges related to the flood threat, aquatic and riparian ecosystem restoration, and recreation opportunities in the corridor. The removal of vegetation, rapid urban development, alteration of flows, and invasion of exotic species have affected both terrestrial and aquatic habitats in the lower Chacon Creek watershed. This appendix provides background information on the biological resources of the lower Chacon Creek watershed and the results of a baseline assessment of the availability of habitats for common wildlife for the Chacon Creek Feasibility Study, which identifies potential measures that could be implemented to reduce the risk of flooding and restore degraded aquatic ecosystems. Specifically, this ECR updates information from the 2007 Feasibility Study report and provides a current analysis of soils, current and historical vegetation communities and wildlife populations, threatened and endangered species, and other pertinent natural resources information applicable to restoration measures and potential flood reduction measures. A 2007 Feasibility Study (Chacon Creek, Laredo, Texas, Draft Feasibility Report and Environmental Assessment) provided an assessment of the suitability of habitats for wildlife species following Habitat Evaluation Procedures (HEP). Five Habitat Suitability Index (HSI) models were selected for the 2007 assessment and approved by the United States Fish and Wildlife Service (USFWS) following a site visit and meeting. In 2017 a HEP analysis was performed to update conditions described in 2007 and provide current information regarding the quality and quantity of available habitat for target wildlife species. The analysis performed in 2017 using the same five species selected in 2007 to evaluate existing habitat conditions in each of five cover types in the study area. Three species models were used to develop models in two cover types. These data were used to determine the suitability of existing habitats based on one or more of the seven HSI models. The availability of habitat is provided as a function of area and suitability. The complete HEP report and associated species tables is presented in Addendum A and a detailed explanation of HEP methodology is described in the following sections below. STUDY AREAS The study area is located in the City of Laredo, Texas in the Lower Chacon Creek corridor, which is situated in the larger San Ambrosia-Santa Isabel watershed (8-digit Hydrologic Unit Code (HUC) 13080002) within the Lower Rio Grande Valley (LRGV) (Figure 1). The lower Chacon Watershed is Chacon Creek, Laredo, Texas, Feasibility Report and Environmental Assessment PUBLIC DRAFT 1 Ecosystem Restoration approximately 37.8 square miles and is defined as the sub-basin downstream from Casa Blanca Lake. The Laredo International Airport is located immediately west of Casa Blanca Lake and is in the northern part of the Lower Chacon Creek watershed. Average elevation is approximately 430 feet (ft) above mean sea level. The entire Chacon Creek watershed is approximately 155.2 square miles. Tributaries to Chacon Creek below Casa Blanca Lake include Tinaja and TexMex creeks. The proposed environmental components detailed in the study are approximately 550 acres in size. The City of Laredo is just north of the Rio Grande in Webb County, approximately 120 miles south of San Antonio, Texas and is a major trucking route for international trade between the United States and Mexico. The City of Laredo and Webb County are currently experiencing rapid growth causing increased development in the Chacon Creek watershed. 2 PUBLIC DRAFT U.S. Army Corps of Engineers, Fort Worth District Study Areas Figure 1. Lower Rio Grande Valley Suitability for common wildlife was assessed for all habitats within the study area, which includes undeveloped lands and city-owned property within the Chacon Creek floodway south of the spillway at Casa Blanca Lake. Casa Blanca Lake and Chacon Creek are located along the eastern and southern edge of development associated with the City of Laredo. A majority of the study area is bordered by residential and commercial development. Although much of the watershed west of Chacon Creek and a substantial portion of lands adjacent to the study area are within the 100-year floodplain and have been developed, a large portion of the watershed east of the creek and north of Casa Blanca Lake remains relatively undeveloped. Lower Chacon Creek is situated in the within the Texas-Tamaulipan thornscrub within the southern Texas plains ecoregion (Griffith et al. 2004) and experiences a hot semi-arid climate (Kottek et al., 2006). Average annual precipitation is 19.6 inches (PRISM, 2004). The area is characterized by drought-tolerant, small-leaved, and often thorny small trees and shrubs. Native vegetation in the study area includes upland plant communities consisting of disturbed honey mesquite (Prosopis glandulosa) and prickly pear (Opuntia spp.) savannas with low vegetation diversity and little structural diversity. Common understory shrubs include Brazilian bluewood (Condalia hookeri), lime pricklyash (Zanthoxylum fagara), Texas persimmon (Diospyros texana), lotebush (Ziziphus obtusifolia), spiny Chacon Creek, Laredo, Texas, Feasibility Report and Environmental Assessment PUBLIC DRAFT 3 Ecosystem Restoration hackberry (Celtis ehrenbergiana), kidneywood (Eysenhardtia texana), coyotillo (Karwinskia humboldtiana), Texas paloverde (Parkinsonia texana), anssacahuita (Cordia boissieri). Typical upland xerophytic species located on hillsides and gravelly ridges include blackbrush (Vachellia rididula), guajillo (Senegalia berlandieri), and Texas barometer bush (Leucophyllum frutescens). Riparian vegetation communities in the study area vary in structure and species composition. Riparian species consist of an herbaceous layer containing an assemblage of native and non-native species, however the area is dominated by invasive grasses and most sites lack herbaceous species diversity. Common riparian plant species consist of sugarberry (Celtis laevigata), cedar elm (Ulmus crassifolia), and Mexican ash (Fraxinus berlandieriana), and codominant stands of salt cedar (Tamarisk spp.), Mexican sabal palm (Sabal mexicana), and Mexican ash (Fraxinus berlandieriana). Hydric habitats support black willow (Salix nigra), black mimosa (Mimosa pigra), common reed (Phragmites australis), giant reed (Arundo donax), and hydrophytes such as cattails (Typha spp.), bulrushes (Scirpus spp.), and sedges (Carex spp.). A list of plant species recorded during 2017 field surveys is provided in Addendum B. RESOURCE SIGNIFICANCE The focus of the U.S. Army Corps of Engineers ecosystem program is aquatic ecosystem restoration. As stated in ER 1105-2-100, “those restoration opportunities that are associated with wetlands, riparian and other floodplain and aquatic systems are most appropriate for Corps involvement” (USACE 2000). The Policy Guidance on Authorization and Budget Evaluation Criteria for Aquatic Ecosystem Restoration Projects summarizes budgetary significance criteria to include scarcity, connectivity, special status species, plan recognition, and self-sustainability. These criteria are further discussed in EC 11-2-187, which defines the specific requirements for rating the criteria. Scarcity Scarcity refers to the scarcity of the habitat to be restored and is based on trend information and relative abundance of the habitat. According to estimates, Texas has lost approximately 52 percent of its wetlands (Teal and Johnston, 2004). Wetlands are known to provide important ecological functions including flood control, water quality improvements, and increases in biodiversity, and to provide valuable tourism and educational opportunities as well. Wetlands provide habitat for birds and are well known for being good bird watching areas and for providing important nursery habitat for a variety of aquatic species (Teal and Johnston, 2004). Additionally, the study area is within the Tamaulipan brushland ecosystem, which is limited to portions of south Texas and northeastern Mexico. The extent of riparian areas in the in the Tamaulipan brushland ecosystem of southern Texas plains has been severely diminished by various land use activities. Most native Tamaulipan brushland has been cleared and converted to agricultural land uses and only 1 percent of riparian areas in this ecosystem are intact (Jahrsdoerfer and Leslie 1988). Only about two percent of this ecoregion remains as intact habitat, and most of the remaining area has been heavily altered by human activity. This ecoregion contains no habitat blocks larger than 96 square miles and lacks protected areas. Only small patches of the original 4 PUBLIC DRAFT U.S. Army Corps of Engineers, Fort Worth District Resource Significance landscape remain. These remnants are largely isolated and provide little opportunity for species dispersal (World Wildlife Organization, 2009). The 2007 ECR surveyed and evaluated habitat within the study area and presented baseline environmental conditions, in which degraded wetland, aquatic, riverine, and riparian shrubland habitats were identified within the study area. The 2007 ECR used the Index of Biological Integrity (IBI) to evaluate aquatic habitat for wildlife, which included a baseline fisheries survey using data collected in 2006.