**Hydro-Geomorphic Classification and Potential Vegetation Mapping for Upper Mississippi River Bottomland Restoration**

Charles H. Theiling1, E. Arthur Bettis2 and Mickey E. Heitmeyer3 *1U.S. Army Corps of Engineers, Rock Island District, Rock Island, Illinois, 2University of Iowa, Department of Geoscience, Iowa City, Iowa, 3Greenbrier Wetland Services, Advance, Missouri, USA* 

#### **1. Introduction**

162 Studies on Environmental and Applied Geomorphology

Woodroffe, C.D. (2002) "Coasts: form, process and evolution". Printed in UK, University

Ecosystem restoration that incorporates process and function has become well known among ecosystem restoration practitioners (Society for Ecological Restoration, 2004; Palmer et al., 2005; Kondolf et al., 2006;). It has been recommended for the Upper Mississippi River System (UMRS; Figure 1) by expert advisory panels (Lubinski and Barko, 2003; Barko et al., 2006) and in Federal policy (U.S. Water Resources Development Act 2007, Section 8001). Our conceptual model for the UMRS integrates process and function among five Essential Ecosystem Components (EECs; Harwell et al., 1999), with hydrology, geomorphology, and biogeochemistry strongly influencing habitat and biota (Lubinski and Barko, 2003; Jacobsen, in press). The primary ecological driver of large floodplain river landscapes is hydrology (Junk et al., 1989; Poff et al., 1997; Sparks et al., 1998; Whited et al., 2007; Klimas et al., 2009), with discharge and river stage being the most common indicators of system condition and variability. Hydrology and hydraulics are conditioned by the geomorphic setting, or geomorphic landscape, which establishes river stage and floodplain inundation response to variable discharge (Clarke, et al., 2003; Thoms, 2003; Newson, 2006; Stallins, 2006; Thorp et al., 2008). Geomorphology is frequently presented as planform aquatic features (i.e., channel, secondary channel, backwater, floodplain, etc.), the river cross-section, floodplain topography, or soil profiles and maps. Flood inundation patterns are mapped less frequently, but they are strongly influenced by both regional and local hydrology and geomorphology (Thorp et al., 2008).

The UMRS is an institutional designation that includes the Upper Mississippi River Valley (UMV), the Illinois River Valley (IRV) and small parts of several tributaries (U.S. Water Resources Development Act 1986, Section 1103) which together span about 1,200 miles of 9 foot deep channels (Figure 1; USACE, 2004a). Channel clearing and stabilization under Federal authority began in 1824 and culminated with 37 lock and dam sites and thousands of channel training structures (USACE, 2004a). Chronic and sporadic shoaling requires dredging every year despite construction of low head navigation dams and channel regulating structures.

Hydro-Geomorphic Classification

Ecosystem Synthesis.

and Potential Vegetation Mapping for Upper Mississippi River Bottomland Restoration 165

The entire river-floodplain covers more than 2.6 million acres (Theiling et al, 2000). The river includes four large "floodplain reaches" (Figure 2) defined by large scale valley features and social impacts (Lubinski, 1999). There are also 18 "geomorphic reaches" which were defined using riverbed slope, valley and channel features, and tributary confluences (WEST Consultants, Inc, 2000; Theiling, 2010). Geomorphic reach characteristics are important determinants of environmental response to development and floodplain land use objectives. Floodplain reaches and geomorphic reaches are analogous with Functional Process Zones and River Reaches, respectively, defined by Thorp et al. (2006, 2008) in their River

Floodplain development occurred concurrent with European settlement and industrialization. Increased shipping demand and the introduction of steamboats consumed massive amounts of wood from the floodplain (Norris, 1997) and necessitated channel improvements to carry larger loads during low flow periods and droughts. When forests were cleared for fuelwood and lumber, agriculture moved in to exploit the rich alluvial environment. Individual farmers connected natural levees to increase crop success initially

and later constructed formal levee and drainage systems (Thompson, 2002).

Fig. 2. Upper Mississippi River geomorphic scaling includes large, glacial controlled floodplain reaches, fluvial geomorphic controlled reaches, and structured (river mile) or

Levees (Thompson, 2002; USACE, 2006), water diversions (Starrett, 1971), and dams (Chen and Simmons, 1986; Fremling et al., 1989) were completed at system-wide scales to manage the distribution and conveyance of surface waters to control flooding, dilute municipal

political (levee district) segmentation schemes.

Fig. 1. Upper Mississippi River System locks and dams and pool reaches.

Fig. 1. Upper Mississippi River System locks and dams and pool reaches.

The entire river-floodplain covers more than 2.6 million acres (Theiling et al, 2000). The river includes four large "floodplain reaches" (Figure 2) defined by large scale valley features and social impacts (Lubinski, 1999). There are also 18 "geomorphic reaches" which were defined using riverbed slope, valley and channel features, and tributary confluences (WEST Consultants, Inc, 2000; Theiling, 2010). Geomorphic reach characteristics are important determinants of environmental response to development and floodplain land use objectives. Floodplain reaches and geomorphic reaches are analogous with Functional Process Zones and River Reaches, respectively, defined by Thorp et al. (2006, 2008) in their River Ecosystem Synthesis.

Floodplain development occurred concurrent with European settlement and industrialization. Increased shipping demand and the introduction of steamboats consumed massive amounts of wood from the floodplain (Norris, 1997) and necessitated channel improvements to carry larger loads during low flow periods and droughts. When forests were cleared for fuelwood and lumber, agriculture moved in to exploit the rich alluvial environment. Individual farmers connected natural levees to increase crop success initially and later constructed formal levee and drainage systems (Thompson, 2002).

Fig. 2. Upper Mississippi River geomorphic scaling includes large, glacial controlled floodplain reaches, fluvial geomorphic controlled reaches, and structured (river mile) or political (levee district) segmentation schemes.

Levees (Thompson, 2002; USACE, 2006), water diversions (Starrett, 1971), and dams (Chen and Simmons, 1986; Fremling et al., 1989) were completed at system-wide scales to manage the distribution and conveyance of surface waters to control flooding, dilute municipal

Hydro-Geomorphic Classification

as follows:

are exhibited in Pools 3 to 13.

and Potential Vegetation Mapping for Upper Mississippi River Bottomland Restoration 167

frequent in the modern era. The Valley's floodplain has been mapped to document the relative age of geomorphic surfaces and associated deposits to help manage cultural resources (Bettis et al., 1996). The studies developed Landform Sediment Assemblages (LSA) which are mappable landforms and their underlying deposits that occur with predictable characteristics (Figure 3; Hajic, 2000). U.S. Department of Agriculture (USDA) soil maps are widely available, but generally lack detail in frequently flooded parts of the floodplain.

Geomorphic mapping in the Valley generally followed the protocol defined by Bettis et al. (1996) with slight variations. U.S. Geological Survey topographic quadrangle maps, aerial photos, soils maps, boring records, and literature were used to construct geomorphic maps. Geomorphic classifications were done at several different scales which allows for more detailed site-specific analysis than reported here. Mapping under modern aquatic areas was not possible and most of the low elevation features (active floodplain and some paleofloodplain) were inundated in the lower ends of navigation pools 2 through 13 between Minneapolis, Minnesota and Clinton, Iowa. We unioned four separate LSA data sets (Bettis et al., 1996; Madigan and Schirmer, 1998; and Hajic, 2000) and reclassified them using a common classification scheme in GIS. The data were clipped to the bluff to bluff floodplain extent (Laustrup and Lowenburg, 1994). LSAs were summarized using a river mile segmentation floodplain overlay. River mile segments are unequal because the width of the floodplain varies and there are curves in the river that create wedge-shaped polygons. These results are a first approximation and open to further interpretation. Higher resolution mapping and analysis will be required for site-specific studies (Heitmeyer, 2010), but this generalized classification matches flood inundation mapping, historic land cover mapping,

Our LSA geomorphic classification has nine classes described below. Characteristics were derived from Bettis et al. (1996), Madigan and Schirmer (1998), and Hajic (2000) and mapped

• **Modern Aquatic Classes** (Modern Channel, Modern Backwater) are primarily the result of navigation dams that inundated low elevation active and paleo-floodplain geomorphic classes, leaving levees and ridges exposed as islands in impounded aquatic areas in Pools 2 to 13. Aquatic area is generally <10 percent of the total floodplain area south of Rock Island, Illinois, but 20 to 60 percent in the north upstream from Rock Island. Modern aquatic area ranges from a few hundred to over 1,800 acres per river mile. Aquatic area is <500 acres for most river mile segments except at Illinois River miles where large lakes occur and on the Mississippi River where impoundment effects

• **Active Floodplain – Poorly Drained** is low elevation floodplain of vertical accretion origin that would have been or is flooded most years. These areas are often associated with tributary confluences. Soils are likely silt, loam, clay mixes that grade downward to coarser sand and pebbly sand. Fine sediments may be 1 – 2 meters deep over coarser sediment. These surfaces are inundated in the lower portions of all navigation pools. Some of these areas occur riverward of the flood control levees where they are exposed to altered hydrology and material transport. Similar areas behind levees are isolated from the river and may maintain more of their historic characteristics. Active floodplain is most abundant in the mid valley Mississippi River reaches and lower Illinois River. That is likely due to the limited effects from impoundment and the drainage of low

and regional habitat assessments (Theiling et al., 2000) quite well.

elevation floodplain in agricultural drainage districts.

pollution, support navigation, and enhance habitat. The outcomes of these changes differ depending on location in the river system (Theiling and Nestler, 2010).

Alterations to hydrology, geomorphic structure, and direct impacts from historical land use change have substantially altered the form and function of ecological communities and processes in the UMRS. The flow of energy is a critical function in ecosystems and alterations to energy pathways can cascade through ecosystems in many ways (Welcomme, 1979; Vannote et al., 1980, Ward and Stanford, 1983; Junk et al., 1989; Ward et al., 1989). Early formal models for stream ecosystem energetics emphasized linear pathways transporting and utilizing metabolic energy differently along a river continuum (Vannote et al., 1983). The early stream ecosystem conceptual models were then tailored to account for nutrient cycling (Newbold et al., 1982), anthropogenic disturbances (Ward et al., 1999), different types of rivers (Junk et al., 1989; Wiley and Osborne, 1990), internal processes (Thorp et al., 1994), watershed influence (Benda et al., 2004 ), and geomorphic structure (Thoms, 2003). We developed system scale data to focus on the relationships expressed in the hydrogeomorphic methodology (Brinson, 1993; Klimas et al., 2009) and the River Ecosystem Synthesis (Thorp et al., 2006, 2008). Land cover, aquatic area, hydrology, and geomorphology data were derived for the entire UMRS for historic, contemporary, and simulated conditions. They can be compared among functional units such as Functional Process Zones or Hydrogeomorphic Patches defined by Thorp et al. (2008) or reference conditions (Nestler et al., 2010; Theiling and Nestler, 2010; SER, 2004) to create simulations of potential vegetation communities under alternative management scenarios.

Ecosystem restoration initiatives require estimates of the natural resource benefits that may be achieved by alternative project plans or project features to ensure accountability and success in Federal projects (USACE, 2000). Recent guidance also calls for the use of adaptive management in Federal water resource planning (Section 2039 of U.S. Water Resources Development Act 2007; Council on Environmental Quality, 2009). The models described here are important elements of adaptive management because they can estimate anticipated outcomes for comparison during monitoring and evaluation stages of the adaptive management cycle (Christianson et al., 1996; Walters, 1997; Williams, 2009). Many restoration plans include plant community or habitat models that estimate community response to physical forces (U.S. Water Resources Council, 1983; USACE, 2000; Council on Environmental Quality, 2009). Predicted plant and habitat response can then be used to support species or community habitat suitability models (USFWS, 1980). Dynamic physical forces are well known ecological drivers in large rivers (Doyle et al. 2005). Methods and data presented here can help estimate physical-ecological cascades resulting from hydrologic and geomorphic alteration of large rivers. We have made great progress developing data needed for potential vegetation models for the entire system. We also discuss the need for a rigorous landscape analysis that includes forest composition in the pre-settlement land cover data.
