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flow recommendation. No flow recommendations have been less than the 7Q10 flow. The New England Method, as adapted for use in North Carolina, uses the September median daily flow as the instream flow recommendation. The standard recommendation from the North Carolina Wildlife Resources Commission and the U.S. Fish and Wildlife Service is that a flow equal to the September median be provided, or a site-specific in- stream flow study must be conducted. Field methods are used to develop instream flow recommendations when potential impacts are high, the stream contains a high quality fishery, or the project will involve peak power production. A site- specific study may be conducted by a developer to determine if an earlier desktop recommendation can be lowered or to provide answers to "what if" ques- tions during negotiations. Field study methods used by the Division of Water Resources include wetted perimeter, regression model, incremental wetted surface area, and the IFIM. A State and Federal interagency team conducts a site visit and deter- mines the most appropriate field methods to be used. Wetted perimeter is one of the more frequently used field methods. Stream cross-sections, or tran- sects, are selected to represent all habitat types contained in the stream reach of interest. The bottom profile of each transect is surveyed relative to a benchmark. Stream discharge and water sur- face elevations are measured at a minimum of three different flows so that a stage-discharge relation can be developed for each transect. Plots of transect wetted perimeter and stage are used to find the point of inflection (water surface elevation at which further reductions in stage result in large losses of wetted perimeter). The discharge corresponding to the water surface elevation of the point of inflection becomes the recommended flow for each transect. Through habitat mapping of the stream reach of in- terest, the percentage of the stream represented by each transect or the stream reach coefficient is detennined. These stream reach coefficients and the sensitivity of each transect to stage reductions are used to weight each individual transect recommen- dation and develop the overall flow recommendation for the study site. The wetted perimeter method is fairly inexpen- sive, and the time required for data collection can range from 2 days for a regulated stream to more than a year for remote sites on unregulated waters. Data analysis requires only 2 to 3 days. Because this method does not consider depth or velocity of water, any portion of the channel under water is considered habitat. Disadvantages of the method include sub- jective identification of point of inflection and the USE OF MULTIPLE METHODS 41 flow recommmendation representing only a single flow of the entire year. There is no way to evaluate the relation of flow to habitat at flows above or below the recommendation. The regression model method is another field approach that was developed to provide a wetted perimeter recommendation. Numerous parameters from over 50 study sites across the State were analyzed for their correlation with the wetted perim- eter recommendation at each site. To develop an instream flow recommendation, the model requires only mean annual flow, 7Q10, and average width at wetted area-discharge point of inflection. Validation analyses for new sites showed that the model predicts well for Piedmont streams. This method requires only one field visit to select and survey transects. No discharge measurements are needed, and the survey data can be collected during any season except during high water. The disadvantages are the same as for the wetted perimeter method. The incremental ~etted surface area method was developed as an improvement to the wetted perim- eter method. Field data collection is the same as for the wetted perimeter method. For a given discharge, this method calculates the wetted surface area at each transect (wetted perimeter x length of stream represented by the transect), and the procedure is repeated for all flows of interest. Plots of wetted sur- face area versus discharge are developed for each transect and the entire study site to indicate flow versus habitat relation. The point of inflection on a plot of wetted surface area for the overall study site is usually the recommended flow. Individual transect plots can be checked to determine the amount of wetted surface area at the recommended or other flows. The time needed to complete field data col- lection for this method is the same as for the wet- ted perimeter method; data analysis then requires 4 to 5 days. The main advantage of the incremental wetted surface area method is that it provides an indication of how wetted surface area changes over a wide range of flows. Its main disadvantage is that any immersed channel is considered habitat. The IFIM is considered the state-of-the-art method for instream flow analyses and is widely accepted and used. It is used for projects that (1) are expected to have significant impacts, (2) may affect an out- standing fishery, or (3) are proposed as peaking hydropower producers. It is also used where com- plicated negotiations will be required to arrive at the recommended stream flow regime. Depth, velocity, substrate, and cover are all used in developing the flow versus habitat relation. The IFIM requires more field time and considerably more data analysis time than previously described field methods. Conse-