VIRGINIACARTER U. S. Geological Survey Reston, VA22092 DONALDL. MALONE JAMES H. BURBANK Tennessee Valley Authority Chattanooga, TN 37401 Wetland Classification and Mapping in Western Tennessee Seasonal color IR photographs provide sufficiently detailed information to map wetland areas as small as 0.5 ha in size and 20 'm in width. INTRODUCTION maps will provide baseline information for resource management including the infor- HE U.S. GEOLOGICAL SURVEY (USGS) and ,,tion needed for T the Tennessee Valley Authority (TVA) legislative or regulatory requirements; have recently completed a cooperative wet- location of seasonally inundated and land mapping project in western Tennessee. permanently flooded areas; ABSTRACT:The U.S. Geological Survey and the Tennessee Valley Authority have recently completed a cooperative wetland mapping project in western Tennessee. High-altitude color infrared photo- graphs were acquired by the National Aeronautics and Space Ad- ministration during several seasons in 1974 and 1975. These photo- graphs supplied the information on hydrologic boundaries and vegetation that was needed for classification and mapping. Seasonal information was required to map the maximum number of cate- gories. The stage (water level) was determined for the time of over- flights for sites where gaging stations are in operation. A wetland classification system was developed for the Tennessee Valley Region based primarily on vegetation, and on frequency and duration of inundation. Using this new classification system, wet- lands at four sites were mapped at 1:24 000 scale as overlays on U.S. Geological Survey 7.5-minute topographic maps. Adjacent land use was also mapped, but in less detail than wetlands. The meth- odology for separating and delineating wetland classes was care- fully documented. Overlays for separate dates were combined to make the final camera-ready composite overlay. A lithographed map of wetlands and land use was made for one of the five quadrangles covering the Reelfoot Lake site. At the Reelfoot Lake and Hatchie River sites, the stage at time of photography was referenced to a stage-duration curve, placed on the map collar, to show that boundaries are repre- sentative of average water levels rather than extreme highs or lows. This experimental project was initiated in decisions on sites for agricultural, resi- response to local, State, and Federal man- dential, or industrial development; agement needs and concern over the loss of wildlife management and habitat acquisi- wetland habitat in the area. The wetland tion; PHOT~GRAMMETRICENGINEERISG AND REMOTESENSING, Vol. 45, No. 3, March 1979, pp. 273-284. PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1979 development of recreational opportunities; mapping the proposed wetland classes and and subclasses as well as surrounding monitoring change in vegetative cover or land use in the Tennessee ValIey Region; wetland acreage and (3) use seasonal photographs to study wet- Recent studies and publications have land boundary dynamics (changes in shown that high-altitude color infrared (IR) hydrologic conditions) and to relate photographs can be used for Level I1 land- boundaries to stage (water level). use and land-cover mapping (Anderson et This report addresses objective 2, and its 1976; Stevens, 1973; Stevens 1974) al., et al., primary emphasis is on the preparation of and for more detailed mapping of inland wetland maps for four sites in western Ten- wetland vegetation cover types (Neilsen and Wightman, 1971; DeSteiguer, 1977; Carter nessee using the wetland classification sys- tem developed for the Tennessee Valley and Stewart, 1977; Carter et al., 1976). The Region. The wetland classification system use of high-altitude color IR photographs to will be discussed only in sufficient detail to document surface-water boundaries has been discussed by Carter and Stewart (1977) explain map preparation. and Moore and North (1974). The authors acknowledge the assistance of personnel from the Reelfoot Lake National Three major objectives of this project were Wildlife Refuge, the Hatchie River National Wildlife Refuge.-, and the Tennessee Wild- develop a wetland classification system life Resources Agency. The USGS office in for the Tennessee Valley Region; Nashville, Tennessee collected water quality test the utility of seasonal high-altitude data at Reelfoot Lake and compiled and (1:130 000 scale) color IR photographs for interpreted stage information. TABLE1. COMPARISONOF WETLAND CLASSES AND SUBCLASSESFOR THE TENNESSEEVALLEY REGION WITH USGS LEVELI1 CATEGORIES(ANDERSON et al., 1976) Tennessee Valley Region Wetland Classes Wetland Subclasses Level I1 Class FW-1 Bottomland (FW-la) Upper Forested Wetland Hardwood Bottomland Hardwood (FW-lb) Lower Bottomland Hardwood FW-2 Swamp (FW-2a) Forested Swamp (FW-2b) Shrub Swamp (FW-2c) Dead, Woody Swamp M-1 Marsh (M-la) Wet Meadow Non-Forested Wetland (M-lb) Emergent Marsh (M-lc) Seasonally Emergent Marsh M-2 Seasonally (M-2a) Vegetated Dewatered Flats (M-2b) Non-Vegetated M-3 Agriculture ngriculture Subject to Flooding OW-1 Open Water (OW-la) Vegetated dpen Water (OW-lb)Non-Vegetated WETLAND CLASSIFICATION AND MAPPING IN WESTERN TENNESSEE 275 the uscs land-use and land-cover classifica- tion system (Anderson et al., 1976) which was used for mapping adjacent land use. An For maximum utility of wetland maps, abbreviated definition of each class is in- the classification system used should meet cluded below, but subclass descriptions and state and local requirements and also be the lists of indicator species have been compatible with a regional or national sys- omitted for the sake of brevity. Figure 1 tem. Existing wetland classification sys- shows the entire Tennessee Valley Region tems were considered: some were too where the classification system is con- general to supply needed management in- sidered applicable. formation (Martin et al., 1953; Penfound, 1952), and others were not really applicable to the Tennessee Valley Region (Stewart Bottomland Hardwood (FW-1): and Kantrud, 1971; Golet and Larson, 1974). Wetland dominated by mixed hardwood Therefore, a new system was developed species and flooded annually during winter based primarily on vegetation and on fie- and(or) early spring. Flooding may be brief quency and duration of inundation (Carter or for long periods. The ground is usually and Burbank, 1978). Several modifications exposed in summer and fall although soil were made in the initial system as the map- may be saturated or covered locally with a pability of the classes was tested. The final few centimetres of water. system is, thus, designed to derive the opti- Swamp (FW-2): mum blend of interpretable and mappable Semipermanently or permanently flooded wetland information from the data source, in wetland dominated by woody vegetation this case high-altitude color IR photography. such as water tolerant deciduous trees, At the same time every attempt was made to aquatic shrubs or saplings, or dead trees provide a classification system useful for and shrubs. those engaged in ground inventory or habitat Marsh (M-1): evaluation. The U.S. Fish and Wildlife Ser- Wetland dominated by herbaceous emer- vice (FWS) has recently published an admin- gents. Flooding may be seasonal (generally istrative draft report on the new national for long periods in late winter and spring), wetland classification system (Cowardin et semipermanent or permanent, or it may be al., 1977) and our system appears to be temporary with soils remaining saturated for compatible with theirs. The Cowardin Sys- most of the year. tem was not used primarily because it was Seasonally Dewatered Flats (M-2): in an early stage of development when the Flats located along the margins of streams project began in 1974. and reservoirs and covered with water dur- Table 1 shows the wetland classes and ing most ofthe year. They may be uncovered subclasses and indicates how they fit into for varying amounts of time in periods of FIG.1. Tennessee Valley Region, showing entire area included in wetland classification system. PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1979 SCALE OF MILES WHC I I I 20 10 0 20 40 60 FIG.2. Location of wetland sites: (1)Reelfoot Lake, (2) Duck River dewater- ing area, (3) Hatchie River Bottoms, and (4) White Oak Swamp. low water or by artificial lowering of water banks. In late winter and spring, and for levels (generally during late summer or short periods following very heavy rain, a fall). These flats become vegetated when wide area of forested flood plain and some exposed for a sufficient period of time before surrounding agricultural land is flooded. the first killing frost. The two remaining sites are in the Ten- Agriculture Subject to Flooding (M-3): nessee River basin and are more or less Lowland areas usually under cultivation affected by controlled water levels in the during the growing season but generally river. The Duck River dewatering area, flooded each year during winter and early located where the Duck River enters the spring. Tennessee River, is surrounded by a levee Open Water (OW-1): and the water level is controlled by TVA. Water up to 3.3 m deep, usually associated Many acres of agricultural land in the area with any of the other wetland classes. Sur- are flooded annually and, until recently, a face vegetation (rooted floating-leaved or program for control of vegetation for wild- free-floating aquatics) and (or) submergent life enhancement was carried on by TVA. aquatics may be present. White Oak Swamp is west of the Tennessee River. White Oak Creek has been channel- ized and dredge spoil piled on the channel Four test sites, Reelfoot Lake, Hatchie banks. The few connections left between River Bottoms, White Oak Swamp, and the main channel and low areas behind the Duck River dewatering area, were selected spoil banks are mostly dammed by beavers. for classification and mapping. These sites Impounded water has created many acres of (Figure 2) are considered representative of Dead Woody Swamp, partially regenerated the diversity of wetlands found in the Ten- to Shrub Swamp and surrounded by For- nessee Valley Region.