Author's personal copy Integrated analysis of PALSAR/Radarsat-1 InSAR and ENVISAT altimeter data for mapping of absolute water level changes in Louisiana wetlands Jin-Woo Kim a , Zhong Lu b , Hyongki Lee a, ⁎, C.K. Shum a , Christopher M. Swarzenski c , Thomas W. Doyle d , Sang-Ho Baek e a Division of Geodetic Science, School of Earth Sciences, The Ohio State University, Columbus OH, USA b U.S. Geological Survey, Vancouver WA, USA c U.S. Geological Survey, Louisiana Water Science Center, Baton Rouge LA, USA d U.S. Geological Survey, National Wetlands Research Center, Lafayette LA, USA e Department of Civil Engineering and Environmental Sciences, Korea Military Academy, Seoul, South Korea abstract article info Article history: Received 4 March 2009 Received in revised form 17 June 2009 Accepted 20 June 2009 Keywords: InSAR Satellite radar altimetry Wetland Absolute water level change Interferometric Synthetic Aperture Radar (InSAR) has been used to detect relative water level changes in wetlands. We developed an innovative method to integrate InSAR and satellite radar altimetry for measuring absolute or geocentric water level changes and applied the methodology to remote areas of swamp forest in coastal Louisiana. Coherence analysis of InSAR pairs suggested that the HH polarization is preferred for this type of observation, and polarimetric analysis can help to identify double-bounce backscattering areas in the wetland. ENVISAT radar altimeter-measured 18-Hz (along-track sampling of 417m) water level data processed with regional stackfile method have been used to provide vertical references for water bodies separated by levees. The high-resolution (~40 m) relative water changes measured from ALOS PALSAR L-band and Radarsat-1 C-band InSAR are then integrated with ENVISAT radar altimetry to obtain absolute water level. The resulting water level time series were validated with in situ gauge observations within the swamp forest. We anticipate that this new technique will allow retrospective reconstruction and concurrent monitoring of water conditions and flow dynamics in wetlands, especially those lacking gauge networks. © 2009 Elsevier Inc. All rights reserved. 1. Introduction Modern landscapes are highly fragmented based on ownership priorities and land-use preferences. The Lower Mississippi River valley is an important economic corridor of agricultural, fisheries, forestry, and oil and gas enterprises that have contributed to a highly dissected landscape of natural and built levees and dredged canals aiding access, transport, and flood control. Efforts to reconnect dissected parcels into larger conservation planning units for the benefit of wildlife and floodway management require more comprehensive knowledge of how water resources are stored and exchanged between these segregated land units. In most cases, knowledge of water levels and flow patterns is lacking due to insufficient monitoring or gauge equipment on private and public lands within floodplain settings. Existing gauge networks maintained by State and Federal agencies are almost exclusively placed in navigable rivers and rarely in backswamp areas behind flood control levees. Only in recent decades have wetland scientists realized the lack of hydrological coupling in adjoining land units within and between floodways and the need for explicit monitoring of backswamp water levels. Unfortunately, the resources are lacking to deploy and maintain extensive gauge networks that would improve our understanding of the hydrological coupling within highly dissected floodplain settings. The Lower Atchafalaya River basin is a major distributary diverting nearly 30% of the Mississippi River flow through forested and marsh wetlands at the coastal margin of the Gulf of Mexico. During high floods these wetlands receive nutrient-enriched river water that is believed to be beneficial for plant growth and for reducing the nutrient load that contributes to offshore hypoxia. Because these wetlands are also near sea-level in upper estuary settings, they are also prone to meteorological tides and surge events from landfalling tropical storms. Remote satellite telemetry observations are being used to interpret water level conditions in oceanic and inland settings. Forest cover and habitat type complicate the ability to use any one remotely sensed platform or instrument for accurate water level reconstructions. New methodologies and protocols are needed to use combined remotely sensed observations to improve our ability to monitor continuous water level or distinguish habitat type or other characteristics of wetland environments. Remote Sensing of Environment 113 (2009) 2356–2365 ⁎ Corresponding author. Division of Geodetic Science, School of Earth Sciences, The Ohio State University, 275 Mendenhall Laboratory,125 South Oval Mall, Columbus, OH 43210, USA. Tel.: +1 614 292 2269; fax: +1 614 292 7688. E-mail address: lee.2444@osu.edu (H. Lee). 0034-4257/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.rse.2009.06.014 Contents lists available at ScienceDirect Remote Sensing of Environment journal homepage: www.elsevier.com/locate/rse