Bohemia River Site

Appendix 5 - Chesapeake Bay Site

Address: Terrapin Nature Area Stevensville, MD (see Maps 1,2)

General Location Description: The site is located on Kent Island on Chesapeake Bay approximately .3 miles north of the Bay Bridge. The area is part of Terrapin Nature Area. The general area is used for recreation with no upland structures. Landward of the project site is a un-improved dirt road (see Maps 1 and 2 for vicinity and project site locations). As depicted in Exhibits 1, and 1a the riparian land uses both upstream and downstream of the site are Forested / Scrub, Shrub and Grass, respectively.

Erosion Potential: As reflected in Exhibit 5 (Historical Shorelines) the project site has historically experienced accretion over the two most recent time periods. However, as reflected in Exhibit 5a is the significant erosion losses indicated between the two previous time periods extending back to early 1900’s. This depicts a dramatic reversal in factors affecting shoreline change over time. Exhibit 7 depicts historical littoral currents prior to the construction of the Bay Bridges, showing net drift to the south. However, with the construction of the approaches to the bridges the post-littoral currents were altered affecting the erosion and accretion patterns. The approaches act as a groin in the retention of materials that have accumulated since its construction. This is indirectly suggested by bottom patterns as reflected in Exhibit 1a. To this extent historical shoreline changes are not a good indicator of present day erosion.

However, strong wave action as suggested by a fetch length of over 10 miles to the north, northwest (see Exhibit 9) in the direction of prevailing winter winds (see Exhibit 10) establish a high-energy environment and resultant potential erosion.

A second factor determining the erosion potential is the soil characteristics landward of the MHW line. The soil composition landward of the shoreline within the riparian area of the project site consists of a peat(see Exhibit 8, 8a). This material has a moderate susceptibility to being eroded as expressed in Exhibit 8a.

Description of Erosion Control Project: The Beach Prisms span a distance of 788 feet consisting of 57 Beach Prisms 4 foot high x 4 foot wide x 10 feet long. Spacing between units ranged from 3 feet at the northern portion of the structure to 5 feet at its southern terminus. Terrapin Nature Area was used as a “test site” for determining optimum spacing between Beach Prisms. As such the Beach Prisms were set in three distinct groups based on spacing as follows; a southern grouping covering 265 feet containing 18 Beach Prisms spaced at 5 feet, a middle grouping covering 266 feet containing 19 Beach Prisms spaced at 4 feet, and a northern grouping covering 257 feet containing 20 Beach Prisms spaced at 3 feet with last two Beach Prisms angled at 45 degrees to the shoreline. Over the last 20 years the Beach Prisms have maintained alignment for the exception of three units that were located in the southern grouping. Pictures 1 through 3 view the beach prisms from north to south. Exhibits 3 and 3a are consistent with field observations of adjoining sites depicting a bulkhead to the north and riprap to the south.

Assessment: Performance of the Beach Prisms is based on the bank and buffer conditions behind the structure and adjacent properties both upstream and downstream of the structure. The bank conditions (see Picture 2) indicate a highly stabilized and vegetated bank with a fringing beach which is consistent with characterizations in Exhibit 2 and 2a. However, Exhibits 2 and 2a characterize the beach as suffering high erosion. This characterization is in conflict with the co-occurrence of a stabilized bank. Potentially, this was an error based on visual observation of different offsets from the shoreline of the structure at its northern and southern ends. As based upon these observations and archival information, the Beach Prisms used in this context have demonstrated protection against wave action. However, the five-foot spacing at the southern end where Hurricane Isabel moved three units out of alignment has created “alignment issues” that could cause future errors.

APPENDIX 1

Onsite Survey 1) Date and Conditions The site was surveyed on August 24, 2009 at approximately 11:40am. There was a one foot water chop. Winds were light out the NW. Skies were mostly sunny. High tide occurred at 8:35am. 2) Project Description The Beach Prisms span a distance of 788 feet consisting of 57 Beach Prisms 4 foot high x 4 foot wide x 10 feet long. Spacing between units ranged from 3 feet at the northern portion of the structure to 5 feet at its southern terminus. The alignment of the structure is north, northeast to south, southwest at slight angle to the shoreline. In addition, at the northern end 2 Beach Prisms were angled 45 degree landward (see Picture 1). At the angle point a distance of 35 feet was measured to the shoreline at time of the survey. The southern end of the Beam Prisms terminated at the shoreline. Pictures 1 through 3 view the Beach Prisms from north to south. 3) Site Description a) The beach is located at the southern portion of the Terrapin Nature Area. b) Vegetated bank in the near shore area ranged in height to 5 feet (see Picture 2) c) A fringing beach ranged in width of 15 feet to north to 5 feet in the south at the time of the survey. d) Depths ranged from 2 feet at the Beach Prism to 3.0 feet at a distance of 100 feet channelward of the Beach Prism. e) A soil profile taken at the base of the Beach Prism was homogenous to depth of 12 inches and consisted of hard packed sand. APPENDIX 2

Archival Information Exhibits 1) Riparian Land Use 1, 1a a) At Site: Forested / Scrub, Shrub b) Upstream: Forested c) Downstream: Grass 2) Bank and Buffer Conditions 2, 2a a) At Site: i) 0 - 5 bank / low erosion, total bank coverage ii) beach / high erosion iii) Phragmites australis b) Upstream: i) 0 - 5 ft bank / low erosion, total bank coverage ii) beach / high erosion iii) Phragmites australis c) Downstream: i) 0 - 5 ft bank / low erosion, total bank coverage 3) Shoreline Features 3, 3a a) At Site: Breakwater b) Upstream: Bulkhead c) Downstream: Riprap 4) Submerged Aquatic Vegetation 4 a) At Site: 0% b) Upstream: 0% c) Downstream: 0% 5) Historical Shorelines 5, 5a a) At Site: accretion (as based two most recent time periods) b) Upstream: accretion c) Downstream: none detect 6) Bathymetry 6 7) Littoral Drift 7 8) Soils 8, 8a 9) Fetch Length 9 10) Wind 10