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The Importance of Woody Material in NW Florida

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Frances Stone, Barbara Albrecht | West Florida Canoe and Kayak Club
Published Monday, August 03, 2009

A program presented to the West Florida Canoe and Kayak Club in Pensacola at the July 2009 meeting by Barbara Albrecht, Aquatic Ecologist for the Nature Conservancy; and Donald Ray, a Stream Ecologist from the Florida Department of Environmental Protection. The report below was written by Frances Stone (Paddlesolo) with assistance from Barbara Albrecht.

Opening the presentation was a definition of a watershed which is the entire geographical area drained by a river and its tributaries; an area characterized by all runoff being conveyed to the same outlet. The characteristics of watersheds include surface flow from rain (runoff), groundwater flow (springs), and connection between surface areas and groundwater in the form of lakes, creeks, wetlands, seepage slopes, small intermittent tributaries and the main river itself. Charateristics of watersheds in NW Florida also include a water table that is very close to the surface (in some coastal areas the ground water may be inches from the top of the soil), an average of 65” of rain a year (often in the form of several inches in less than 1-2 hours), and primarily sandy soil. The highest flows occur in the summer and early fall, frequently precipitated by hurricanes. Human activities which have altered the natural characteristics of watersheds (hydrology) over a period of time by fragmentation, this includes farming activities, logging, development, and most especially road building.

The next part of the presentation included descriptions of the area prior to development by primary sources which included William Bartram who described the landscape in the late 1700s, John Landreth in the early 1800s, the Duke of Saxe-Weimar Eisennach in 1825 and 1826, and Dr. Charles Mohr at the turn of the 19th century.

The remarkable timber diversity found in varying ecotones (different habitat types) became a huge source of revenue for the area, and resulted in Pensacola becoming the largest deep water harbor in the Gulf Coast. Lumber was shipped to every foreign port, and many of the castles in Europe were built with NW Florida lumber. The principals of conservation and sustainability were not followed at that time.

Early efforts to restore some of the damage were begun and carried out by the Civilian Conservation Corp (CCC).  In the Conecuh National Forest, located north of the Blackwater River Stave Forest, the CCC was solely responsible for replanting and restoration of erosion caused by the clearing of trees beginning in 1936 and continuing until 1942. The CCC projects that helped the environment were erosion control, planting Longleaf and Slash Pines, and fighting wildfires. The practices of agriculture and logging many years ago, coupled by development and sprawl via roads have significantly affected our streams at the present time and was documented by numerous pictures of eroded stream banks, muddy turbid waters, silty streams, and inappropriate fish passages which all impact the organisms dependant on local rivers.

The removal of woody material (snags) is especially detrimental to the physical structure of the river, and is one cause of bank erosion.  Another cause of bank instability is the removal of the trees which in a healthy river/stream/creek system line the banks (these trees live in the riparian zone which protect the banks in times of flooding).The diversity of the trees that live in the riparian zones dictate the species of aquatic insects the system supports.  Historically, the riparian zone was dominated by hardwoods made up of Beech, Magnolia, Sweet Gum, Poplars, Hickory, Ash, Maples, Black Walnut, and dogwoods.  The lowlands were predominantly made up of Cypress, who had adapted to living in the water.  The leaf matter built up on the forest floor and during rain events washed into the creeks.  Dense canopies of trees overhanging the smaller tributaries provided leaf matter and woody material by falling into the creeks and ultimately providing food for the smallest organisms in the foodweb.  These organisms in turn provided food to the fish, crawfish, snakes, alligators, and other animals found in these systems.  The densely woven root-mats protected the banks, and when the rains came and washed everything into the creeks, this material washed downstream into the bays and basins to provide nutrients to the seagrasses and the system responsible for providing our fisheries and seafood.

The bottom line is that small animals and larvae that can live in clear clean water, cannot exist in water that carries fine-silty sediment.  Once the smallest organisms vanish, so too do fish and birds, since they do not have food to thrive on.  This explains why one doesn't see many water birds along the streams with big sandbars such as Big Juniper Creek, Blackwater River, and Coldwater Creek.  While the highly eroded banks along these streams make for great photographs, and paddlers love taking a break on the sandbars, they don't help the stream because during every rain events, more sediment from unpaved roads is washed downstream. These sediments ultimately cause streams to become wide and very shallow.

This has happened to the upper Perdido River where land clearing has removed the riparian system and ultimately is the reason it has so many log jams.  The pine trees continue falling into the river when the banks erode, but the water is so shallow they can't float downstream, so they pile up.. I asked about Big Alaqua Creek after the meeting because member Judy Russell said it was always muddy, and found out that many of the creeks on Eglin have been historic bombing targets in the past which have caused damage to the lower watershed over the years.  In addition, Eglin's main mission is to use their land for range activities - and this requires removal of vegetation. Vegetative control removes the root mats and leaf matter which control sediment erosion, and ultimately allow sediments to wash down into creeks.  Eglin has an active BMP (best management practices) program in place to address sedimentation in area creeks and is currently addressing all of the watersheds on their 480,000 acre landscape.  Through the knowledge of ecologists like Donald Ray, Eglin has now altered their practices and moved their targets to upland habitats.  As a result of their commitment to their river and stream diversity, Eglin now has three full time aquatic biologists on staff to address these type of issues and restore areas from past activities.

Today our rivers and streams contain less than 5% woody material, historically our rivers contained upwards of 50%.  Also, rivers meander and are sinous in nature because this slows down water and allows woody material to gather in bends and also slow the water flow thus curbing erosion.  During the peak lumber/timber harvesting period, many of our rivers and creeks were straightened to assist loggers in floating the timber to the mills.  Really kind of hard to imagine that men using just their backs and oxen could change the shape and flow of the river. The Chipola River has a natural bridge that historically was used as a crossing point for the river, but blocked the ability to float lumber downstream.  A canal was dug and is still present today.  It is narrow, straight, and has fast moving water.  You can see it south of the boat landing in Florida Caverns State Park.  It is closed to paddlers to allow the woody material to fall in the stream and turn this into a more natural - even though still man-made - stream segment.

Last update Monday, August 03, 2009

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