Pacific County Shoreline Analysis Report 5 ANALYSIS OF ECOLOGICAL CHARACTERISTICS 5.1 Methods A GIS-based semi-quantitative method was developed to characterize the relative performance of relevant ecological processes and functions by shoreline reach, within the County, as outlined in WAC 173-26-201(3)(d)(i). The assessment used the available information gathered as part of the shoreline inventory and applied ranking criteria to provide a consistent methodological treatment among reaches. These semi-quantitative results will help provide a consistent treatment of all reaches in approximating existing ecological conditions, yet allow for a qualitative evaluation of functions for data that are not easily summarized by GIS data alone. The results are intended to complement the mapped inventory information (Appendix B) and numerical data (Table 4-3) and provide a comparison of watershed functions relative to other reaches in the County. The analysis of the ecological characteristics of the Coastal Ocean AU is different than the analysis for the other AUs. The main distinguishers for the Coastal Ocean AU are that 1) the Coastal Ocean AU does not contain distinct shoreline segments, and 2) there is a paucity of data on the dynamic, biophysical characteristics in the AU, so they are supplemented with human use data as proxies for nodes of ecological function. Reach Delineation In order to assess shoreline functions at a local scale, the ten AUs with upland areas within the County were broken into discrete reaches based on a review of maps and aerial photography. The Coastal Ocean AU is considered as a singular section (i.e., no distinct reaches) for this assessment. While there certainly is spatial heterogeneity in the uses and ecology of the Coastal Ocean AU, the boundaries that define the distinct activities are dynamic. The following criteria were used to determine reach break locations for marine, riverine, estuarine, and lacustrine shorelines (Table 5-1). In many locations in Pacific County, the precise transition between estuarine and riverine characteristics cannot be determined by mapping alone, therefore, in areas of limited development, a single reach may encompass areas with both estuarine and freshwater riverine characteristics. Land use (e.g., adjacent land use patterns, shoreline uses, vegetation coverage, and shoreline modifications) was weighted heavily in determining reach break locations, in recognition that 124 The Watershed Company May 2015 the intensity and type of land use will affect shoreline ecological conditions. Furthermore, functional analysis outcomes will be more relevant for future determination of appropriate shoreline environment designations if the reach breaks occur at possible transition points in environment designations. In addition to land use, physical drivers of shoreline processes were used to establish an overall framework for determining reach break locations. Regardless, reaches have been created for informational purposes only and are not intended to represent regulatory boundaries. While reach scale analysis of ecological functions is one aspect of evaluating appropriate environment designations, several other inventory elements, including land use characteristics, also play a significant role. The total number of reach breaks by AU is described in Table 5-2. Table 5-1. Criteria for Determining Reach Breaks Marine/Estuarine Riverine Lacustrine4 Changes in land use1 Changes in land use1 Changes in land use1 Changes in vegetation Change in shore type Stream/River confluences (coverage and type) Changes in vegetation Changes in channel confinement Significant wetland areas2 (coverage and type) and upland topography Creek/River mouths Tributary confluences Changes in topography Changes in vegetation Artificial barriers (levees, dikes) (coverage and type) 1. Reach breaks were generally identified at the nearest parcel boundary, except with large parcels, where physical or ecological factors changed notably within a single parcel. 2. In general, reach breaks were positioned to avoid dividing large wetlands. Table 5-2. Summary of Reaches per Assessment Unit Assessment Unit Number of Reaches 1- North River 13 2- Willapa River 22 3- Middle Bay 9 4- Naselle River 17 5- Upper Chehalis Basin 3 6- Grays River 4 7- Columbia River 7 8-Willapa Bay 21 9- Long Beach Peninsula 13 10- Pacific Coast- North 3 11- Coastal Ocean 1 In order to evaluate salt marsh and eelgrass vegetation, as well as aquaculture activities that occur below the ordinary high water mark, reach boundaries were extended waterward using the GIS Euclidean Allocation tool. Euclidean Allocation divides the non-source space (for example, Willapa Bay) into zones based on closest proximity to the shoreline reach. Because 125 Pacific County Shoreline Analysis Report these zones are determined according to Euclidean, or straight-line, distances, boundaries were adjusted to better represent natural breaks, such as channel centerlines in Willapa Bay (Figure 5- 1). Generally, associated wetlands were included in the reach functional analysis when any portion of the wetland fell within 200 feet of a shoreline. For the analysis, reach boundaries were also extended to include areas of associated wetlands that occur west of SR 103 on the Long Beach Peninsula and west of SR 105 on the North Pacific Coast, as past studies and management approaches have confirmed hydrologic connectivity of these wetland areas. Figure 5-1. Example of estuarine zones created through the Euclidean Allocation process. Approach The analysis of reach functions was based on the four major function categories identified in the Department of Ecology’s guidelines: hydrologic, hyporheic, shoreline vegetation, and habitat. The four primary functional categories were further broken down into relevant functions identified in WAC 173-26-201(3)(d)(i). Table 5-3 provides a brief description of each function, potential effects of land use, and potential indicators for each function from available spatial data, as well as areas of typical human disturbance. 126 The Watershed Company May 2015 Table 5-3. Summary of Shoreline Ecological Functions Shoreline Processes Functions, Impacts, and Indicators Type Storage of peak flows is provided by floodplains, off channel areas and large wetland complexes; these features help reduce peak flows and contribute to summer low flows. Whereas landslides and bank failures typically contribute sediment in steep upper reaches; overbank flooding, localized bank erosion, and bedload transport represent the major sediment transport processes in lower reaches. Land use impacts: Vegetation removal alters the water/sediment balance and destabilizes slopes resulting Riverine in excess bed or bank erosion and disconnected floodplains. Encroachment into floodplains and floodways by structures or fill reduces the local flood storage capacity, resulting in increased flood heights and velocities. Shoreline armoring limits local bank erosion. Dams affect hydrologic processes at a watershed scale. Available Data Indicators: Floodplains, Floodways, Armoring, Road density, Dams, Wetlands Water storage functions of lakes can help attenuate the severity of downstream flooding. Sediment storage functions alter downstream sediment budgets. Water and Land use impacts: Artificial dams alter the seasonal storage of water and limit sediment transport Lacustrine downstream. sediment processes Hydrologic Available Data Indicators: Dams Sediment transport processes are affected by freshwater inputs, tides, waves, and wind. Sediment erosion and accretion processes are responsible for the formation of estuarine and marine habitats including salt marshes and sand dunes. Land use impacts: In-water structures and shoreline armoring alter sediment transport processes. Dikes restrict tidal exchange and tidegates result in muted exchange. Armoring of natural bluffs restricts natural erosion, which would otherwise contribute to the sediment balance within the bay or drift cell. Development Marine/ can affect groundwater recharge rates by concentrating and channelizing stormwater and filling wetlands. Estuarine Groundwater well withdrawals can also affect groundwater levels. Dredging and dredge disposal alters water flow and sediment transport processes. Incidental structures related to boating and commercial and recreational fishing can also alter sediment transport processes. These incidental structures include things such as shipwrecks, derelict gear, and other fixed structures. Available Data Indicators: Armoring, Dikes, (Comprehensive tidegate data not available) 127 Pacific County Shoreline Analysis Report Shoreline Processes Functions, Impacts, and Indicators Type Floodway and floodplain areas and riverine wetlands provide a transition between upland and riverine habitats. Vegetated uplands help to desynchronize flooding impacts downstream. Broad, vegetated floodplains help slow and disperse flood flows. Riverine Land use impacts: Armored or leveed shorelines tend to accelerate flow, increasing erosional forces downstream. Available Data Indicators: Floodplains, Floodways, Forested vegetation in floodplain, Armoring, Levees Shallow gradient shorelines help attenuate wave energy, limiting shoreline erosion and providing sheltered, shallow-water habitat. Emergent and woody vegetation helps attenuate wave energy. Land use impacts: Armored shorelines create a steep shoreline gradient, and tend to reflect wave energy Lacustrine Energy toward adjacent shoreline areas or the lake bed.