T73 Ecological Implications of Headwater Channel Processes

Monday, 3 November 2003
8:00 AM - 12:00 PM

DERANGED DRAINAGE IN APPALACHIAN HEADWATERS IMPACTED BY SURFACE COAL MINING AND RECLAMATION

Paper number: T73-7
Program: Technical Sessions
Time: 8:45 AM – 9:00 AM

Authors

Abstract

Low-order streams in the incised dendritic drainage networks of North-Central West Virginia and adjacent Pennsylvania have been radically altered by surface coal mining and subsequent reclamation. All of our study sites have been mined and reclaimed since the passage of the Surface Mine Control and Reclamation Act (SMCRA) of 1977, and all are considered “good” examples of how to meet SMCRA Approximate Original Contour (AOC) requirements. However, field and GIS investigations show that AOC is very far removed from original landscape form and function. Specific drainage transformation varied greatly with the somewhat-age-dependent variable of reclamation style. Drainage density for 1st and 2nd order streams decreased in all cases, but this trend was somewhat mitigated at sites where sediment trenches were retained after mining and act as low-gradient low-order streams. Many new reclamation sites lack any small streams, relying entirely on subsurface groundwater and overland flow to deliver water to streams that were 3rd or 4th order prior to mining. Many 1st or small 2nd order streams in unmined uplands have been severed from the rest of the fluvial system by broad reclaimed slopes lacking any designed surface drainage.

The long-term stability of this “deranged” drainage remains in doubt. Groundwater and sheet-flow routes lack conveyance to handle moderate- to high-magnitude runoff from intense rainfall. Steeper slopes commonly show significant gully development very soon after reclamation, and observations suggest these gullies fore-tell long-lived channel paths across reclaimed slopes. We conclude that existing reclamation practices inadequately address the important roles of small streams in storm-water conveyance and sediment transport, and virtually eliminate ecological functions critical to the biological viability of all streams throughout a watershed.