CRAB-MIT Sea Grant College Charting Project Update 8/15/2016

Since the last update, there has been a lot of activity.

Funding: We have received contributions from the Boston Duck Tours, the Head of the Charles Regatta, Newton Yacht Club, Riverside Boat Club, and a few generous individuals. Loads and loads of thanks to them all. This has allowed us to buy most of the equipment we need for the project. The MIT Sea Grant College Program has been a great partner in this effort, buying some equipment we could not afford and providing the funding for a summer intern. We still need more help with funding. Please consider making a contribution and send your checques to:
      Dave Amicangioli
      CRAB Treasurer
      25 C Street
      Belmont, MA 02478
Thanks in advance for your support!!!

Depth Measurements: The MIT Sea Grant Program has been actively making sonar depth measurements. They have made a handful of passes up and down the river between the BU Bridge and Newton YC, each at a slightly different position along the width of the river. Detailed measurements of the river near both Newton YC and Watertown YC have also been made. Nearly the entire area between the New Charles River Dam and the BU Bridge has been measured using both conventional and side-scan sonar. This includes all the sites that the Charles River Conservancy has recently identified as potential locations for a swimming facility.

Bottom Composition Measurements: While the time delay of the sonar pulse back to the sensor allows the depth to be characterized, the strength of that same signal is characteristic of the river bottom. Thusly, we are able to generate maps of both the depth and the hardness of the river bottom. We can clearly see areas that appear to be hard rock or clay and other areas where it is likely softer mud or even softer plant growth.

Characterization of the Variation in the Height of the Watersheet: As most users of the river know, there is some variation in the height of the watersheet over the course of the day. With an outgoing tide, water from the river is released into Boston Harbor through sluices at the New Charles River Dam, and as the tide comes back in, the sluices are shut and water begins to accumulate in the river. In order to accurately quantify the water depths, we need to also know what the height of the watersheet is when we make any depth measurement. In early July, stream gauges and data loggers of the water depth were installed at Riverside Boat Club, Herter Park, and Community Rowing. We are also able to use data from the USGS gauge at First Street below the Longfellow Bridge. It appears that the water level in the section of the river between Watertown and the New Charles River Dam has been changing nearly uniformly this summer. That is, this section of the river appears to be behaving as a lake, rising and falling in near unison. This is probably due to the lack of rainfall that we have experienced this year. We are adjusting the measured depths to account for the variation in the height of the water sheet using the data from the stream gauge at Riverside Boat Club.

Deliverable Outputs: In designing this project, we have focused on what we would be able to provide to users of the river.

• Chart Booklet: A printable PDF file that includes an overview of the river from Watertown to Boston Harbor, and more detailed charts of 13 abutting or overlapping sections of the river. Separate booklets for water depth and river bottom hardness would be available.
  
• Google Map and Google Earth: We have developed on-line versions of our data using both Google Maps and Google Earth that allow us to use all the tools of Google Map and Google Earth to digitally visualize the data.
  
• Trifold Overview: Similar to the trifold map developed by the Charles River Conservancy showing the parkland surrounding the river, this trifold would include an overview of the river showing the depth and the hardness of the river bottom.
  
• Electronic Versions for Navigation Instruments: Due to the lack of a common standard file format and the complexity and difficulty of generating multiple file formats, we have decided to delay this until we can get other things done first.