Hydrologic Connectivity of Floodplains, Northern Missouri-Implications for Management and Restoration of Floodplain Forest Communities in Disturbed Landscapes

Abstract

Hydrologic connectivity between the channel and floodplain is thought to be a dominant factor determining floodplain processes and characteristics of floodplain forests. We explored the role of hydrologic connectivity in explaining floodplain forest community composition along streams in northern Missouri, USA. Hydrologic analyses at 20 streamgages (207–5827 km2 area) document that magnitudes of 2‐year return floods increase systematically with increasing drainage area whereas the average annual number and durations of floodplain‐connecting events decrease. Flow durations above the active‐channel shelf vary little with increasing drainage area, indicating that the active‐channel shelf is in quasi‐equilibrium with prevailing conditions. The downstream decrease in connectivity is associated with downstream increase in channel incision. These relations at streamflow gaging stations are consistent with regional channel disturbance patterns: channel incision increases downstream, whereas upstream reaches have either not incised or adjusted to incision by forming new equilibrium floodplains. These results provide a framework to explain landscape‐scale variations in composition of floodplain forest communities in northern Missouri. Faust () had tentatively explained increases of flood‐dependent tree species, and decreases of species diversity, with a downstream increase in flood magnitude and duration. Because frequency and duration of floodplain‐connecting events do not increase downstream, we hypothesize instead that increases in relative abundance of flood‐dependent trees at larger drainage area result from increasing size of disturbance patches. Bank‐overtopping floods at larger drainage area create large, open, depositional landforms that promoted the regeneration of shade‐intolerant species. Higher tree species diversity in floodplains with small drainage areas is associated with non‐incised floodplains that are frequently connected to their channels and therefore subject to greater effective hydrologic variability compared with downstream floodplains. Understanding the landscape‐scale geomorphic and hydrologic controls on floodplain connectivity provides a basis for more effective management and restoration of floodplain forest communities. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Flood regime typology for floodplain ecosystem management as applied to the unregulated Cosumnes River of California, United States

“…However, although flooding is recognized as an essential component of the natural flow regime, assessing variability in flood characteristics is often not a focus of management despite ecological outcomes. This is exemplified in Jacobson and Faust (2014), who showed that although flood frequency and duration followed expected patterns on the Missouri River, floods that should have inundated floodplains did not due to channelization and incision. This is exemplified in Jacobson and Faust (2014), who showed that although flood frequency and duration followed expected patterns on the Missouri River, floods that should have inundated floodplains did not due to channelization and incision.…”

“…Furthermore, environmental flow science rarely considers how the surrounding landscape-often highly modified environments-can influence the ecological performance of a managed flow regime (Arthington, Bunn, Poff, & Naiman, 2006;Yarnell et al, 2015). This is exemplified in Jacobson and Faust (2014), who showed that although flood frequency and duration followed expected patterns on the Missouri River, floods that should have inundated floodplains did not due to channelization and incision. As land and water management decisions are often interdependent, analysis of altered flood regimes should be examined jointly with modification of the physical landscape (Kondolf et al, 2006).…”

A hydrogeomorphic classification of connectivity of large rivers of the Upper Midwest, United States

“…Bankfull flows are best determined on-site as the discharge that just starts to inundate the floodplain, but for this extensive regional assessment we use the simplifying assumption that, on average, river floodplains in quasi-equilibrium with their channels are inundated every 1.5 to 2 years (Leopold, 1994). Of course, actual extent of inundation of the floodplain is affected by factors such as levees and channel incision or aggradation that can disrupt equilibrium and alter the average return interval for floodplain inundation (Jacobson and others, 2011;Jacobson and Faust, 2014). To represent a more conservative threshold of floodplain inundation of bankfull flow we have used the 50-percent annual exceedance probability flood (or 2-year recurrence interval), calculated from the partial duration series of peak flows using the U.S. Geological Survey PeakFQ program (Flynn and others, 2006).…”

“…For small rivers and for some streamflow-gaging stations, the vertical dimension of surface-water hydrology can be explored explicitly and empirically through a streamgagedischarge rating curve. Such data can be used to determine the stage threshold when surface water goes over bank to connect to the floodplain and to calculate hydrologic metrics (exceedances, durations, seasonality, for example) for that threshold condition (Jacobson and Faust, 2014). Extrapolation of hydraulic conditions from streamflow-gaging sites to reaches or segments between gages can be tenuous, however, depending on the geomorphology of the gaged cross section compared to variability along the river.…”

Partitioning Among Niche and Neutral Explanations for Metacommunity Patterns in Cerrado Stream Fish Communities

“…: 30] and other aquatic organisms [e.g. : 28,31,32]. The main problem of the use of linear distances is the comparison of streams present in different hydrographic units.…”