# The Definition of Perennial Streams Based on a Wet Channel Network Extracted from LiDAR Data
## 4 Summary and Conclusions  
The purpose of this study was to define perennial streams using the dimensionless relationship between streamflow exceedance probability (\(E_{Q}\)) and the wet channel ratio (\(\alpha_{W}\)) based on wet channel networks extracted from LiDAR data. Based on available LiDAR data and streamflow observations, 30 watersheds were selected, and the valley network and wet channels were extracted from LiDAR topographic data and the signals' intensity of ground returns with a 1 m spatial resolution. The results of the study can be summarized as follows. Using the observed streamflows and the wet channels identified, we derived a power-law relationship between wet channel length and streamflow; the scaling exponent of this relationship was within the range of values reported in the literature. This relationship was \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Watershed.** & **NHD perennial** & **Perennial Stream** & **Perennial** & **(i) \(E_{Q}\) of Perennial** & **(ii) \(E_{Q}\) of Perennial** \\
**Stream Length** & **Ratio** (\%)** & **Streamflow (m\({}^{7}\)/s)** & **Streamflow (\%)** & **Streamflow** \\ \hline Middle Branch & & & & & \\ Chopawamscic Creek, VA & 8.8 & 16.69 & 0.0082 & 72 & 90 \\ \hline North Branch & & & & & \\ Chopawamscic Creek, VA & 9.5 & 11.95 & 0.0092 & 85 & 87 \\ \hline South Branch & & & & & \\ Chopawamscic Creek, VA & 3.5 & 11.18 & 0.0017 & 88 & 99 \\ \hline General Creek, CA & 18.1 & 8.27 & 0.0272 & 100 & 84 \\ \hline Allison Creek, SC & 68.3 & 18.16 & 0.2551 & 68 & 51 \\ \hline Wildcat Creek, SC & 31.6 & 17.87 & 0.0698 & 69 & 72 \\ \hline Pemington Creek, OK & 29.9 & 29.38 & 0.0636 & 49 & 96 \\ \hline Mill Creek, OK & 17.5 & 15.25 & 0.0259 & 75 & 96 \\ \hline Rock Creek, OK & 9.9 & 2.26 & 0.0099 & 100 & 100 \\ \hline Incline Creek, NV & & & & & \\ (Upstream) & 5.4 & 9.70 & 0.0036 & 93 & 100 \\ \hline North Criner Creek, OK & 3.8 & 4.46 & 0.0020 & 100 & 77 \\ \hline Incline Creek, NV & 15.3 & 11.42 & 0.0207 & 87 & 100 \\ \hline Trout Creek, CA & 18.1 & 8.68 & 0.0273 & 98 & 100 \\ \hline Little Washita River, OK & 1.6 & 2.51 & 0.0004 & 100 & 95 \\ \hline Lake Creek, OK & 24.5 & 20.28 & 0.0455 & 64 & 59 \\ \hline Logan House Creek, NV & 4.7 & 21.18 & 0.0028 & 62 & 73 \\ \hline Glenbrook Creek, NV & 6.4 & 12.49 & 0.0047 & 83 & 88 \\ \hline Eagle Rock Creek, NV & 1.8 & 11.86 & 0.0005 & 85 & 100 \\ \hline \end{tabular} (i) \(E_{Q}\) of the perennial stream using the relationship between the wet channel ratio (\(\alpha_{W}\)) and streamflow exceedance probability (\(E_{Q}\)). (ii) \(E_{Q}\) of the perennial stream using the relationship between streamflow (Q) and wet channel length (\(L_{W}\)).  
\end{table} 
Table 2: _Cont._converted into a non-dimensional form using \(E_{Q}\) and \(\alpha_{W}\), and the previous definition of perennial streams using \(E_{Q}\) values of 90% and 80% corresponded to \(\alpha_{W}\) values of 11% and 15%, respectively. The perennial stream ratio was computed for each study watershed to validate the derived \(\alpha_{W}\) associated with the perennial stream definition, and its mean value (i.e., 11%) was within the range of the \(\alpha_{W}\) associated with the definition of perennial streams in this study. Moreover, the streamflow exceedance probability of perennial streamflow for each watershed was calculated, and its mean value (86%) was similar to previous definition values (i.e., 80% and 90%). Although this study attempted to define the perennial stream with relatively limited watershed and LiDAR information, the relationship between streamflow exceedance probability and the wet channel ratio showed significant agreement with previous studies on perennial stream definition. In addition, the results clearly demonstrated the possibility of applying the wet channel ratio as another parameter for defining perennial streams. The relationships determined in this study are likely to be applicable in similar climates (e.g., climate aridity index \(E_{P}/P\) = 0.8-2.1).