Abstract
Anthropogenic development of floodplains and alteration to natural hydrological regimes have resulted in extensive loss of off-channel habitat. Interest has grown in restoring these habitats as an effective conservation strategy for numerous aquatic species. This study developed a process to reproducibly identify areas of former stream meanders to assist future off-channel restoration site selections. Three watersheds in Iowa and Minnesota where off-channel restorations are currently being conducted to aid the conservation of the Topeka Shiner (Notropis topeka) were selected as the study area. Floodplain depressions were identified with LiDAR-derived digital elevation models, and their morphologic and topographic characteristics were described. Classification tree models were developed to distinguish relic streams and oxbows from other landscape features. All models demonstrated a strong ability to distinguish between target and non-target features with area under the receiver operator curve (AUC) values ≥ 0.82 and correct classification rates ≥ 0.88. Solidity, concavity, and mean height above channel metrics were among the first splits in all trees. To compensate for the noise associated with the final model designation, features were ranked by their conditional probability. The results of this study will provide conservation managers with an improved process to identify candidate restoration sites.
Highlights
Restoring floodplain habitat complexity and lateral connectivity with the adjacent stream through the enhancement and creation of off-channel habitats has been recognized as increasingly important for the conservation of both native and endangered aquatic species [1,2,3,4,5]
The growing availability of high-resolution light detection and ranging (LiDAR)-derived digital elevation models has allowed for the development of methodologies to classify target features across wide swathes of the earth’s surface
Our study demonstrated our ability to extract the unique features of relic stream channels, oxbow scars, and oxbows from other riparian depressions across the landscape from LiDAR-derived digital elevation models
Summary
Restoring floodplain habitat complexity and lateral connectivity with the adjacent stream through the enhancement and creation of off-channel habitats has been recognized as increasingly important for the conservation of both native and endangered aquatic species [1,2,3,4,5]. Oxbow lakes may be artificially created after the channelization of a stream bisects its natural meander to isolate it from the new channel. Though oxbow lakes receive much of their water volume during periodic flooding events of the main channel, groundwater percolation is important as it helps protect these habitats from complete desiccation during extended periods of low-flow and disconnection from the stream [17]. Relic stream channels, abandoned oxbows, and stream meanders that were either naturally or artificially disconnected from the channel through processes such as stream channelization or infrastructure development are primary candidates for off-channel habitat restoration as they provide natural depressions that are often closely connected to the groundwater and minimize restoration cost [4,10]
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