Evaluating Concentrated Flowpaths in Riparian Forest Buffer Contributing Areas Using LiDAR Imagery and Topographic Metrics

Abstract

Riparian forest (CP22) buffers are implemented in the Chesapeake Bay Watershed to trap pollutants in surface runoff thus minimizing the amount of pollutants entering the stream network. For these buffers to function effectively, overland flow must enter the riparian zones as dispersed sheet flow to facilitate slowing, filtering, and infiltrating of surface runoff. The occurrence of concentrated flowpaths, however, is prevalent across the watershed. Concentrated flowpaths limit buffer filtration capacity by channeling overland flow through or around buffers. In this study, two topographic metrics (topographic openness and flow accumulation) were used to evaluate the occurrence of concentrated flowpaths and to derive effective CP22 contributing areas in four Long-Term Agroecosystem Research (LTAR) watersheds within the Chesapeake Bay Watershed. The study watersheds include the Tuckahoe Creek watershed (TCW) located in Maryland, and the Spring Creek (SCW), Conewago Creek (CCW) and Mahantango Creek (MCW) watersheds located in Pennsylvania. Topographic openness identified detailed topographic variation and critical source areas in the lower relief areas while flow accumulation was better at identifying concentrated flowpaths in higher relief areas. Results also indicated that concentrated flowpaths are prevalent across all four watersheds, reducing CP22 effective contributing areas by 78% in the TCW, 54% in the SCW, 38% in the CCW and 22% in the MCW. Thus, to improve surface water quality within the Chesapeake Bay Watershed, the implementation of riparian forest buffers should be done in such a way as to mitigate the effects of concentrated flowpaths that continue to short-circuit these buffers.

Are dissolved organic carbon concentrations in riparian groundwater linked to hydrological pathways in the boreal forest?

“…Along the stream networks, the delineation of DRIP/non-DRIP areas in the RZ can help to implement hydrologically adapted buffers in forest management, thereby ensuring that water bodies maintain a good water quality (Kuglerová et al, 2014b;Tiwari et al, 2016;Wallace et al, 2018). Traditionally, forest practices considered fixed width buffers, even though the riparian function is not homogeneous around all water bodies (Buttle, 2002).…”

“…For the hydrological characterization of riparian inputs, various approaches can be used across scales. Although subsurface pathways do not entirely follow surface topography (Devito et al, 2005), it has been demonstrated that topographic depressions are a good indicator of accumulation areas of water, ponding, shallow groundwater tables, and concentrated flow paths in the near-stream area (Ågren et al, 2014;Jencso et al, 2009;Wallace et al, 2018). As such, topographic models can predict where along a stream network disproportionally large amounts of groundwater connect with the stream.…”

Are hydrological pathways and variability in groundwater chemistry linked in the riparian boreal forest?

“…Along the stream networks, the delineation of DRIP/non-DRIP areas in the riparian zone can help to implement hydrologically adapted buffers in forest management, ensuring that waterbodies remain their water quality (Kuglerová et al, 2014b;Tiwari Wallace et al, 2018). Traditionally, forest practices considered fixed width buffers even though the riparian function is not homogeneous around all water bodies (Buttle, 2002).…”

“…The occurrence of saturated areas in the RZ is linked to preferential hydrological pathways that route upland water towards streams. Although subsurface pathways do not entirely follow surface topography (Devito et al, 2005), it has been demonstrated that topographic depressions are a good indicator for accumulation areas of water, ponding, shallow groundwater tables and concentrated flow paths in the near-stream area (Ågren et al, 2014;Jencso et al, 2009;Wallace et al, 2018). As such, topographic models can predict where along a stream network disproportionally large amounts of groundwater connect 35 with the stream (Leach et al, 2017).…”

Spatiotemporal evolution analysis of agricultural non-point source pollution risks in Chongqing, China, based on the ITO3dE model and GIS

“…This tallies with the decrease in chemical fertilizer use intensity and pesticide use intensity, as farmland reduction inevitably lead to a decrease in the application of these substances (Zaragozí et al, 2012), complying with the "one regulatory, two reduction, three basic" policy promoted by the Chinese government. A previous study has analyzed the relationship between the riparian forest buffer zone and pollution mitigation in Chesapeake bay watershed and found that the wide buffer zone could effectively reduce water pollution (Carlington et al, 2018). Other authors have analyzed the relationship between climate, land use change, and water quality in the Pike river watershed and found that land use changes had an impact on water quality (Mehdi et al, 2015).…”