Impact of a meandering river on property size and ownership, Little Wabash River, South Central Illinois, USA. Diane M. Burns and David C. Viertel, Eastern Illinois University, Charleston, IL RESULTS The results demonstrate that there are major discrepancies between what a landowner is listed as owning and what the actual plat size is in both the area defined by the official parcel boundaries and the actual exposed land. Table 1 gives a partial listing of the discrepancies in parcel sizes. The official parcel acreage is a matter of record. An investigation of what the digitized parcel size is via GIS software reveals that these often do not match – the parcel was sold as X acres and the parcel delineated by the boundaries are different. The second revelation was that the actual, exposed land area acreage differs from both the official size of the parcel and the digitized part of the parcel. The repercussions are purely financial in this study – the landowner paid for a parcel that is either smaller or larger than they obtained, and the real estate taxes are either larger or smaller than should be levied. Realistically, the local government agency is not monetarily affected. The total number of acres are taxed consistently; however, the individual landowner may be taxed on acreage they do not have. Additionally, a landowner may have thought they purchased a certain number of acres because of the official parcel size, yet the landowner may have acquired much less land than that for which they paid. On a positive note, some landowners have larger amounts of acreage than what they paid for and are being taxed annually less than they should. ABSTRACT Meandering rivers, often portrayed as lazy, idyllic bodies of restful peace, are actually quite dynamic, constantly shifting their channel pathways in just mere years’ worth of time. Through processes of erosion, flooding, neck and chute cutoffs and avulsion, these rivers migrate laterally tens to hundreds of feet during the course of their existence. Humans have long used river valleys as areas of settlement and farming, as the rich soil deposited in the floodplain adjacent to the river channel is quite fertile and conducive to raising crops. The Midwest of the continental United States is no different, with myriad streams crossing the landscape and home to a huge agriculture industry. Dominant crops are corn and soybean, although the land is used for other agricultural purposes as well. The agricultural industry in Illinois is quite lucrative; the average annual revenue generated from just the corn and soybean crops is $9.7 billion and $5.3 billion, respectively (average of crops ’09 – ’14). Obviously, then, the land is extremely valuable. Many of the land parcel edges were originally delimited by where they meet the river banks. Because rivers meander, the property lines could have been altered since the parcels were first defined. Areas in Effingham, Clay and Coles Counties were examined to what has been the impact on the owners on either side of the channel. Initial research compared aerial photos from 1938 and 2008 Quickbird satellite imagery and ArcGIS datasets to determine how much acreage has been affected. To date, 19 different areas have been identified as having a significant change in size. A significant change has been arbitrarily set at 2 or more acres, chosen because the average farm in Illinois is 10 acres and a loss/gain of 2+ acres would have a large impact. This study investigates the history of ownership on these parcels and the ramifications of changes made by the river’s work on the banks bordering the land. INTRODUCTION Throughout time, rivers meander and change their courses by water flowing actively in the channels. These changes are created geologically and instantaneously through the development of meander cutoffs. Meander cutoffs can form as either chute cutoffs or neck cutoffs, and the mechanisms by which they develop have been examined in past studies (Matthes, 1948; Crickmay, 1960; Ratzlaff, 1981; Mosley, 1975; Gay et al., 1998). These cutoffs arise from the result of headward erosion of gullies during flooding periods. The gullies begin during the initial flooding stage and METHODS Archival aerial images from July 5, 1938 were obtained for the entire length of the Little Wabash River from its headwaters in Coles County to its confluence with the Wabash River (images courtesy of The Illinois Natural Resources Geospatial Data Clearinghouse). Once all of the necessary images were collected and downloaded, they were imported into ArcMap and georeferenced to their proper orientations. Images were sub-divided based on county boundaries. After all images had been processed, the banks of the river channel were outlined via digitization. The archival dataset for Effingham County was compared to Quickbird data from A base map from the online ARCGIS catalog created in July, 2011 was used for the comparison with archival Clay County data. The banks of the river’s channel were also outlined via digitization in these more recent datasets, and the archival and newer datasets were overlain to inspect for changes in the river’s pathway in each county. These comparisons revealed multiple areas in which there had been a significant cutoff produced since the 1938 dataset. Using both Clay and Effingham Counties’ clerk records, specific land parcels along the cutoffs were identified. Using GIS software, two calculations were obtained for each parcel – the area of the land outlined in the county records as the extent of the property and the area of the land exposed in the parcel’s boundaries (parcel boundaries defined by the river’s bank). These areas were then compared to the officially listed size of the landowner’s parcel. DISCUSSION/CONCLUSION Preliminary investigation into the ownership of the plats surrounding the river cutoffs in Effingham County from the earlier study (Burns and Viertel, 2011) showed the edges of the parcels to be coincident with the current river channel, which is a common practice in defining plat boundaries. As we have demonstrated through both previous studies (Burns and Viertel, 2011 and Burns and Viertel, 2014), however, the channel has shifted throughout time. Given the current boundaries, then, plats had to have been redrawn/redefined at some point in time. Unfortunately, it would appear that redefining the edges of the parcels has not kept pace with actual acreage or official designation of acreage. All of the parcels investigated had a discrepancy with either the parcel’s current boundaries or the actual acreage or both – more commonly, it was with both. A large number of the parcels had the edges of their boundaries in the middle of the river channel, which is also problematic. The state of Illinois claims ownership of all surface waters, so the edge of the exposed land is the true and actual edge of the landowner’s property. Figure 1 – graphic showing the study areas in Central Illinois. Parcels were investigated in Clay and Effingham Counties. All parcels investigated were adjacent to the channel of the Little Wabash River. INTRODUCTION (con’t) complete the connection between the two parts of the main channel, creating a pathway through which the stream or river channel will continue to flow (Johnson and Paynter, 1967; Gay et al., 1998). Recent studies have examined the dynamics of changes in flow patterns in the growing meander cutoff as the water diverts from the main channel to the new one (Rhoads et al., 2009) along with the effects on sedimentation patterns and creation of sediment pulses at the cutoff as well as downstream (Zinger et al., 2010; Zinger, Rhoads and Best, 2011). The documentation and research into the physical aspects of meander cutoffs is well advanced; however, minute attention is given to the impact this phenomenon has had on land usage and land ownership as a result of channel shifts. Previous work on the Little Wabash River’s channel migration focused on the river’s passage through Effingham County (Burns and Viertel, 2011) and through Clay County (Burns and Viertel, 2014). In those studies, shifts in the channel location affected over 200 acres of land, although one section is believed to be as a result of human alteration of the path. The current study undertook an analysis of the influences of the meandering on individual landowners’ parcels in terms of actually owned acreage versus the officially registered plat sizes. Figure 2 – graphic showing one of the landowner parcels in Clay County, IL. This parcel is not along one of the significant cutoffs identified in previous studies; this is merely a parcel that is bordered by the Little Wabash River. Even though it was not one of the cutoffs of significance, there are still discrepancies – the listed acreage is 58.35, but a GIS analysis of the boundaries reveals that it is only 56.7 acres. SELECTED CITED REFERENCES Matthes, G.H., 1948, Mississippi River Cutoffs, American Society of Civil Engineers Transactions, v. 113, p. 1 – 39. Crickmay, C.H., 1960, Lateral Activity in a River of Northwestern Canada, Journal of Geology, v. 68, p Ratzlaff, J.R., 1981, Development and Cutoff of Big Bend Meander, Brazos River, Texas, Texas Journal of Science, v. 33, p Gay, G.R., Gay, H.H., Gay, W.H., Martinson, H.A., Meade, R.H. and Moody, J.A., 1998, Evolution of Cutoffs across Meander Necks in Powder River, Montana, USA, Earth Surface Processes and Landforms, v. 23, p. 651 – 662. Johnson, R.H. & Paynter, J., 1967, The Development of a Cutoff on the River Irk at Chadderton, Lancashire, Geography, v. 52, no. 1, p. 41 – 49. Mosley, M.P., 1975, An Experimental Study of Channel Confluences, The Journal of Geology, v. 84, no. 5, pp Rhoads, B.L., Best, J., Johnson, K., and Engel, R.F.,2009, Flow Structure and Channel Change in a Chute Cutoff along a Large Meandering River, AGU Abstracts with Program #H44C-02. Zinger, J.A., Rhoads, B.L., and Best, J., 2011, Extreme Sediment Pulses Generated by Bend Cutoffs along a Large Meandering River, Nature Geoscience. Zinger, J.A., Rhoads, B.L., Best, J., Engel, F., and Konsoer, K.M., 2010, Mobilization of Floodplain Sediments by Chute Cutoffs on a Large River: Lower Wabash River, Illinois-Indiana, AGU Abstracts with Program #EP31C Table 1 – Partial listing of parcels and acreage discrepancies. Figure 3 – graphic showing one of the landowner parcels in Clay County, IL. This one is officially listed as 20 acres. The outline of the parcel actually embraces 22 acres, but the digitized exposed land surface is 21.3 acres. Figure 4 – graphic showing one of the landowner parcels in Clay County, IL. This one is officially listed as 11 acres. The outline of the plat using the river bank as the border reveals that it is actually 14.1 acres; the boundaries make it 17.1 acres.