When The River Floods

This past week the Ouachita River reached bankfull on May 21st, 2021. The river crested at 31.89 feet on May 24th, 2021. Spring floods are common at the farm, but in the past few years, it seems like we are experiencing these floods more often. To back this up with some data, my good friend, Riley Colton, wrote a term paper a few years back that broke down some of the river gauge data over the years to see if there was any change in the frequency of flooding at the Camden gauge. To summarize his findings, the following is an excerpt from the abstract of his paper: “Results indicate a clear increase, from 1960 to 2020, in flood frequencies and precipitation; with an amplified increase since the Partee family took over the property in 2007… Average river heights increased by 13.22%, with a 24.05% increase during vegetation’s growing season. Annual precipitation totals increased by 4.56%, with a 6.31% increase during the growing season. Chances of exceeding river stages, that affect the farm’s vegetation at observed elevations, have all increased since 2007.”

Riley found that there had been an average increase in precipitation and the frequency of the river reaching bankfull when comparing river stages from 1960-2007 to 2007-2020. The one thing to consider with these data sets is that the 2007-2020 data set is a much smaller sample size with a period of 13 years, while the 1960-2007 is a period of 47 years. The most recent data set (2007-2020) may average out differently if we were to continue to collect data for 34 years from now. Regardless of what is to come, we have seen a lot of spring flooding in recent years.

So what does this mean for our management practices and wildlife on the farm? For some species, we may see increases in abundance, but others may see declines. Changes in hydrology affect vegetation communities in bottomland ecosystems that can alter the species that inhabit those communities. Some of our areas that contain willow, nuttall & water oaks have started to transition to overcup oak & cypress communities that are more tolerant to water-logged soils. Beaver activity also plays a role in these areas, as dam building during heavy rain periods has allowed beavers to catch large volumes of water and hold it in these hardwood flats. We try to clear these dams as often as possible, but our efforts are often thwarted by excessive rainfall and frequent river flooding. The GTR unit on the north end of the property is often plugged by beavers when the river drops out, but we have successfully removed these dams within a few days or less of the river receding.

During late April of 2021 we experienced straight line winds that toppled large oak trees in some areas. Water logged soils did not help with the strength of these trees and made it easy for the wind to blow down large red oaks. These openings are starting to grow in river cane and various shrubs, grasses and vines creating viable habitat for songbirds, swamp rabbits, turkeys, etc. but we hate to lose oaks even if it helps create early successional habitat. Everywhere we look in nature we see change and changes in hydrology and climate can alter the survivability and abundance of species within an ecosystem. How we manage and deal with these changes is a never-ending learning process. Our game fish populations seem to be thriving with all of the recent flooding and our wood duck populations last year were some of the largest we’ve ever seen. We even located a hen turkey with 12 or more poults that all appeared to survive into winter. Did the hen nest on high ground outside of the flood waters or did she nest after the flood? Or did the above average precipitation results in more food on the landscape for adults and poults? These are the kinds of things that leave me scratching my head when trying to understand populations and the effects predation, flooding, climate, etc. have on them.

Wild turkeys are what I worry about the most when it comes to more frequent spring flooding. Even on high ground, wet and cool springs can be detrimental to turkey poults. To see how spring flooding is affecting turkey nesting on our farm, I took arcGIS processed lidar data from Riley’s term paper to see how much suitable habitat is inundated by the river at various gauge levels (the map and ground truthing at various stages of the river were used to verify the elevation levels in relation to the river gauge levels).

River Gauge Levels (26’ bankfull) in Relation to Elevation at 3.3’ to 6.1’ Contours:

1- 19.9'-26.0' (Elevation 89’-95.1’)

2- 26.0'-29.3' (Elevation 95.1’-98.4’)

3- 29.3'-32.5' (Elevation 98.4’-101.6’)

4- 32.6'-35.8' (Elevation 101.7’-104.9’)

5- 35.8'-39.1' (Elevation 104.9’-108.2’)

6- 39.1'-42.4' (Elevation 108.2’-111.5’)

7- 42.4'-45.7' (Elevation 111.5’-114.8’)

8- 45.7+(Record Flood 114.8’+)

Clearly we can see areas that are inundated frequently (31’ & below are fairly common) and other areas that are flooded less frequently to varying degrees. Elevation class level ‘4’ is within the bottoms, but would be considered some of the highest ground within the flood plain. If we total the acreage in the elevation class ‘4’ and above, the property contains approximately 300 acres of habitat within these elevation ranges. Elevation class ‘5’ and above are rarely flooded and make up approximately 160 acres of the 1200 acre property.

A few questions I have regarding this subject: Are hens able to locate the highest ground? How successful are their re-nesting attempts? How often do they nest in bottomland sites when compared to upland? How does the timing of the floods affect nest success? At what flood level will a hen abandon a nest? In other words, is there a flooding threshold or do they abandon the nest if water is within a certain distance of the nest? Is the recent increase in spring flooding reducing nest success and or populations?

I could go on and on with questions, but until the day comes when I can strap a GPS unit onto one these birds, I’ll have to rely on field observations. I’ve found nest over the years in elevation class levels ‘3’ & ‘4’ but I don’t find nests that often. Most of the time, I see poults during the late spring and summer and try to make hypotheses as to how and when the nesting occurred.

As far as management goes, because of spring floods, we try to maintain and create excellent nesting habitat on the highest elevations of the property. The lower elevations are often frequented by hens with their brood due to the excellent brood rearing habitat that these lower elevation wetlands can create. It is not uncommon to spot hens and their brood in our moist soil units in mid-late summer bugging around the moist soil vegetation. The mast production from the hardwoods is also of importance during the fall and winter. Flocks of 70 or more birds in the bottoms are not uncommon during the winter, foraging on acorns.