Water Velocity Magnitude and Direction Collected on May 8-9, 2019 at Select Breakwaters in Lake Erie at Presque Isle State Park, Erie, PA

Background: Presque Isle State Park (PISP), located in northwestern Pennsylvania, is located on a 3,127 acre peninsula that extends into Lake Erie. Approximately 7 miles long, PISP is a recurving sand spit where the width of the neck is less than 1,000 feet and the center, eastern end exceeds 1 mile. The park boundary extends 500 feet offshore around the perimeter of the peninsula. The spit forms an embayment, Presque Isle Bay, between its southern shore and the northern shore of the city of Erie. A channel at the east end of the bay is maintained by dredging to permit ship access to the harbor. PISP is considered a unique heritage park as it contains the only "seashore" area in Pennsylvania. Sand erosion, as on any natural shoreline, has always been an issue on the Lake Erie side of PISP. Wave action, littoral currents, and extreme weather events move sand from the neck of the peninsula toward the distal end. In 1986, a plan was developed for shoreline erosion control at PISP and the installation of a series of 55 segmented rubble mound breakwaters parallel to the peninsula shoreline from Beach 1 to Beach 10 began on September 11, 1989. The project was completed on November 20, 1992. From 1993 until the present, annual beach nourishment of lake-dredged sand is required to maintain the beaches behind the breakwaters. Even after the establishment of the breakwater system, coastal storms still have a significant impact to the shoreline and there are safety concerns as result of the existence of the breakwaters and the continual input of new sand into the system. The biggest effect from the breakwater system is sediment deposition behind the breakwaters and cutting off longshore transport to the far eastern end of Presque Isle, resulting in an erosion hot spot at the end of the breakwater system. As the sand erodes and moves eastward down the peninsula, it supports the formation of tombolos, connecting the shoreline to the midpoint of the breakwater with a sand bridge. Tombolos inhibit the flow of water down the shoreline and function as a groin allowing the accumulation of sand on one side and scouring out the sand on the other side. Objective: The objective of this study is to collect baseline data on water-currents within the breakwater system to understand the connection between the angle of approach and the water-currents that would be transporting sediment alongshore. Along with the water current data, data is collected to document a snapshot of the bathymetry within the breakwater system. Methods: Velocity magnitude and direction data were collected with a Sontek M9 Acoustic Doppler Current Profiler (ADCP) in the middle of and between breakwaters from breakwater #19 - 31. The depth of water is collected as well. This data was then processed with the Velocity Mapping Toolbox (VMT) (Parsons et al., 2013) in order to output bathymetry data and velocity vectors. Data Form Summary: The data in each zip file consists of an Excel file that contains data processed within the VMT. Output generally includes a point location, depth, water current velocity, and water current direction at that location. See each individual metadata file included in the zip file for specific details. This data can be input into data software such as ArcMap to create visualizations of the data.

背景：普雷斯克艾尔州立公园（Presque Isle State Park, PISP）坐落于宾夕法尼亚州西北部，地处一处延伸至伊利湖的3127英亩半岛之上。该公园全长约7英里，为一处弧形沙嘴，其颈部宽度不足1000英尺，中部与东端宽度则超过1英里。公园边界向半岛周边海域外延500英尺。该沙嘴在其南岸与伊利市北岸之间形成了普雷斯克艾尔湾（Presque Isle Bay）这一海湾。海湾东端的航道经疏浚维护，以保障船舶进出港口。普雷斯克艾尔州立公园是一处独特的遗产公园，因其拥有宾夕法尼亚州境内唯一的“海滨”区域。与所有自然岸线一样，该公园毗邻伊利湖一侧的沙滩侵蚀问题始终存在。波浪作用、沿岸流与极端天气事件会将半岛颈部的泥沙搬运至远端。1986年，普雷斯克艾尔州立公园制定了岸线侵蚀防治方案，并于1989年9月11日启动1号海滩至10号海滩沿线的防波堤修建工程，该工程为一系列与半岛岸线平行的55段分段式抛石防波堤。工程于1992年11月20日完工。自1993年至今，需每年使用湖底疏浚砂开展防波堤后方海滩的补沙作业，以维持海滩形态。即便建成了防波堤系统，沿海风暴仍会对岸线造成显著影响，同时防波堤的存在以及系统内持续补充的新沙也带来了安全隐患。防波堤系统最大的影响是在防波堤后方造成泥沙淤积，并切断了前往普雷斯克艾尔东端的沿岸输沙通道，进而在防波堤系统末端形成侵蚀热点区域。随着泥沙被侵蚀并沿半岛向东搬运，会形成连岛沙坝（tombolo）——即以沙桥将岸线与防波堤中点相连。连岛沙坝会阻碍沿岸水流，其作用类似丁坝：一侧泥沙淤积，另一侧则发生冲刷。
研究目标：本研究旨在收集防波堤系统内的水流基线数据，以探明来流角度与沿岸输沙水流之间的关联；同时采集数据以快照形式记录防波堤系统内的水深地形（bathymetry）。
研究方法：本研究使用索泰克M9声学多普勒流速剖面仪（Sontek M9 Acoustic Doppler Current Profiler, ADCP），在19号至31号防波堤的中段及各防波堤之间的区域，采集流速大小与流向数据，同时同步采集水深数据。随后利用速度映射工具箱（Velocity Mapping Toolbox, VMT，Parsons等，2013）对采集数据进行处理，以输出水深地形数据与速度矢量。
数据格式概述：每个压缩包内的数据均包含一份Excel文件，其中存储了经速度映射工具箱处理后的数据集。输出数据通常包含测点位置、水深、该测点的水流流速与流向。具体细节请查阅压缩包内附带的各元数据文件。该数据可导入ArcMap等数据分析软件，以生成数据可视化成果。