Identifying stream types and management implications

Characteristics of stream types were surveyed within the Chattooga River watershed in the Blue Ridge Mountains of southeastern US. The 728 km(2) watershed is contained within the states of Georgia, South Carolina and North Carolina. The stream types of about 190 streams of various sizes were determined as perennial, intermittent or ephemeral using a combination of physical and biological indicators. The key indicators were defined as channel erosion into the landscape and aquatic insects. Comparisons were made between the measured stream characteristics and their hydrologic orders. The stream data indicated that most headwater order 1 streams were either ephemeral or intermittent. Order 2 streams were divided among intermittent, perennial and ephemeral. All order 3 streams and larger ones were perennial, except for one small, third order intermittent stream with an 18% channel gradient. The data suggest that the total 4670 km stream network was approximately equally divided between defined channels (28% perennial and 17% intermittent) and undefined channels (55% ephemeral). Changes in stream order produced exponential changes in the total number, mean segment length and total length of streams. The fine detail included about 15,630 order 1 channels with a combined length of 2740 km. Comparisons are provided between the estimated extent of stream types and the 'blue-line' streams identified on the US Geological Survey topographic contour maps at both 1:24,000 and 1:100,000 scales. Streams indicated on the 1:100,000 scale maps identified about 650 km of streams, while the 1:24,000 scale mapped the blue-line stream extent at 970 km. Of the estimated 1300 km of perennial streams, the topographic maps identified 50-75%, depending on scale. However, only about 14-21% of the entire stream network which includes perennial, intermittent and ephemeral streams were marked on the topographic contour maps. Recommendations are included for improving the consistency of how 'stream orders' and 'stream types' are delineated. Since water quality protection measures are often related to the stream type, improvement in identifying streams should improve stream protection design and help to prevent impacts on water quality and aquatic habitat. (C) 2001 Elsevier Science B.V. All rights reserved.