Lower Charles River Flood Plain and Alluvial Soils

With this update, I will examine the lower Charles River Watershed. I briefly touched on the upper and lower Charles River Watersheds in a previous post. The division between upper and lower is drawn at the Watertown dam. Below is a map by the EPA showing the division and boundaries.

Image Source: EPA

The lower Charles River Watershed is dominated by development and heavy human use as the potion of the watershed that contains parts of Boston proper. As you can see, almost the vast majority of the lower basin is actively used by people for residential, commercial, transportation, or recreational uses. There are small patches of marshes, reservoirs, smaller streams, and the river itself but the land is largely developed and impermeable.

Image Source: Image Source: Zarriello, P. J., & Barlow, L. K., 2002

The streams, river, and runoff do deposit sediment for the soil in the lower watershed, but much of the area especially towards the city is artificial fill and urban land (Weiskel, P. et al 2005). The artificial shaping of the land near the city is a longstanding tradition and began in the 1600s when the first European settlers began expanding the city by leveling some of it's famous hills to fill in the land between what was a peninsula and the mainland (Mitchell, J. H. 2008).

Image Source: Zarriello, P. J., & Barlow, L. K., 2002

Below, you can see a map of what the shoreline would look like before the deliberate filling of the bay. Many of the places I visit everyday would simply be water or marsh.

Image Source: Weiskel, P. et al 2005

It is hard to imagine these areas without human development, and like it or not the land has been changed. To improve how this land is used, the work I described in my Special Threats post around preventing Combined Sewage Overflows and strengthening both the infrastructure and preparation for flooding remains a priority. 

Mitchell, J. H. (2008). Paradise of All These Parts: A Natural History of Boston (1st ed.). Beacon Press. Weiskel, P. K., Barlow, L. K., & Smieszek, T. W. (2005). Water resources and the urban environment, lower Charles River Watershed, Massachusetts, 1630-2005. U.S. Department of the Interior, U.S. Geological Survey. Zarriello, P. J., & Barlow, L. K. (2002). Measured and simulated runoff to the lower Charles River, Massachusetts, October 1999-September 2000. U.S. Dept. of the Interior, U.S. Geological Survey. 

The fearsome Water Chestnut

The water Chestnut, or Trapa natans, is a invasive species to the northeast that first touched ground in the US within the Charles Watershed. Below you can find some information I have gathered on this species that overwhelms and smothers ponds, lakes, and streams beneath thick carpets of floating leaves.

Transparency Tube: Better than a Secchi disk?

Several years ago, I had experience as a volunteer and professional collecting water samples. As I started research for this post, I planned to focus on water sampling equipment and tests to make recommendations for an entry level water sampling kit. In that process however, I stumbled on a way to measure turbidity (how cloudy water is) that was new to me. In my days of water sampling, I always used a tool known as a Secchi disk but there is a cool tool called a transparency tube that is a better fit for many purposes.

Measuring the clarity of water is essential to understand how far light can penetrate for photosynthesis, animal visibility, and tracking the particles and nutrients in water.

Secchi Disk:

The Secchi disk is one of the simplest tools an enthusiast or scientist interested in water quality will use. It is made up of a rope attached to a weighted disk, usually colored white and black. To use a Secchi, you simply lower the disk into a body of water slowly until the disk is no longer visible, and then record the depth at which this happened by measuring the length of rope used when lowering. You can buy Secchi disks cheaply as scientific equipment goes, but they are also easy to construct if you want a project to start your first water sampling kit.

To show you how quick and easy taking a measurement with the Secchi Disk is, watch this video.

Video Source: AlaskaSeaGrant

Importantly, Secchi disks are best in bodies of water with deep, slow moving water because if the water is too shallow to reach a point where the disk is obscured or water is moving too quickly for the weighted disk to stay in place the Secchi will not give as accurate a reading of turbidity and water clarity. My experience water sampling was in a bay with slow moving water, both shallow and deep areas, and large variances in turbidity within a brackish estuary. In that environment the Secchi disk was perfect, and easy to train volunteers to use!

Transparency Tube:

The transparency tube is a tool that also measures the clarity of water and is relatively simple to use. In essence, a transparency tube is a transparent tube marked with measurement's along the side, with a valve as well as a miniature Secchi disk inside the base of the cylinder. More details can be found along with the diagram bellow at this link.

Image Source: J. Fetter and K. Koch, 2022

To use a transparency tube, you pour a water sample inside the tube and then slowly release water out the bottom valve until the mini Secchi disk becomes visible. You then record the turbidity according to the marks along the side of the tube at the point when the disk became visible. Transparency tubes normally use a measure called Nephelometric Turbidity Units or NTU. Importantly this scale is not linear and the area between 5 and 10 NTU will be much farther on a tube than 200 and 300 NTU for example. In contrast to Secchi disks, transparency tubes can be used in shallow water or swift flows.

Video Source: Washington Stormwater Center

If you purchase a transparency tube for your water sampling kit, be sure to store the tube with a covering that will prevent any scratches as the tube's transparency is required for accuracy. Likewise recorded the weather and light conditions when taking a measurement outdoors as those conditions can effect results. If the body of water you are interested in studying has slow moving, deep water I would recommend building your own Secchi disk before investing in a transparency tube for sheer simplicity, but these are a great option and provide accurate measurements of water clarity under conditions the Secchi performs poorly.

Special Threats!

With this post, I will highlight several threats to the Charles River Watershed. Most of these topics, I have touched on in previous posts but will expand on here.

Development:

The Charles River watershed runs through one of the biggest cities in the country, and millions rely on the water and services it provides. Around the Boston area, some areas have as much as 80% impervious ground cover creating problems for draining, pollution, runoff, and flooding (CRWA). The following picture is from a map of the impervious surfaces around Boston, This image is from 2005, and there has been almost 2 decades of development since then.

Image Source: Charles River Watershed Association

As mentioned in a previous post, there are 19 dams around the Chares River Watershed. Many of them are in states of disrepair and no longer provide benefit to the people that live here, while also actively harming local ecosystems. These dams have become a focus of ecological and indigenous rights pressure as activists try to get them removed. In the meantime, the local government just approved millions of dollars for repairs and maintenance of dams in 2024.

Water Quality:

The Charles has a bad reputation for it's water quality, even earning the nickname "that Dirty Water" by Standells song Dirty Water. Since 1995, there has been a deliberate push to monitor and improve the water quality of the Charles River with annual ratings from the EPA and work by government and community leaders to clean up that dirty water.

Below is a graphic created by the Charles River Watershed Association for the most recent EPA rating.

Image Source: Charles River Watershed Association

These grades represent how safe the Charles is for recreational use such as boating and swimming. It is only in recent years that swimming in the Charles is becoming a possibility, although swimming is still only allowed in specific areas and under specific conditions. 

A major issue for water quality is Combined Sewer Overflows (CSOs), that lead to sewage being washed into the river and harbor by rainwater. In 2023, 39 CSOs lead to 70 million gallons of stormwater mixed with untreated sewage into the river (Cut the Crap project). You may find an interactive map of CSOs in the Charles HERE. 

Image Source: Charles River Watershed Association

For a different Class, I made a slideshow about a threat to the Charles that I wanted to add here as well. Although I have shown on this blog that the water quality for the Charles has improved, just a few weeks ago we just had the first major cyanobacteria bloom in 4 years. Blooms are created by excessive nutrients released in the water by pollution and waste.

Flooding:

As a result of climate change, participation in the watershed has increased by 60% since 1958 and is expected to increase by up to 78% over the next 50 years (CRWA, 2024). The infrastructure we have is not well equipped to deal with that, but a collaboration between the local governments and community leaders across the watershed, the Charles River Climate Compact, has formed to prepare for and avoid the damage from extreme weather and flooding. This model is one of the compacts first actions and lets you examine the flooding by storms all the way into 2070.

Sources:

Gov. Healey Awards Nearly $14 Million in Funding for Dams and Coastal Infrastructure. (2024, September 26). Charles River Watershed Association. Charles River Watershed Association. https://www.crwa.org/river-current/gov-healey-awards-nearly-14-million-in-funding-for-dams-and-coastal-infrastructure

Cevasco, C. (2019, June 18). Damming Fish and Indians: Starvation and Dispossession in Colonial Massachusetts. The Junto. https://earlyamericanists.com/2019/06/18/damming-fish-and-indians-starvation-and-dispossession-in-colonial-massachusetts/

https://www.crwa.org/cutthecrap 

https://www.crwa.org/climate-compact 

Watershed Heroes Spotlight: the Choctawhatchee Basin Alliance!

The Choctawhatchee Basin Alliance (CBA) is my favorite environmental organization. 

I served two full service years in an AmeriCorps program that partnered with CBA, and was later hired by CBA to work with some of their education programs. They do incredible work for education, restoration, and research around the Choctawhatchee Bay and are great people. Below is a short presentation on the organization and some of what they do!

When the Charles Floods

 Historic Floods:

1938 - This year held a historic flood event for the Charles in the summer and then 2 months later the famous 1938 New England Hurricane caused a second wave of massive damage and flooding.

I found a local TV special about this hurricane where people who lived through the storm told the story decades later. I am from Florida and no stranger to hurricanes, but living through a storm like that without modern weather prediction or news technology to give warning is terrifying.

Documentary Source: NBC 10 WJAR 

1955 - Hurricanes Connie and Diane are two storms that came a week apart in August 1955. Both caused huge damage to New England. Diane left 20 inches of rain in two days and especially severe flooding.

Image Source: NOAA and National Weather Service

March 2010 - The most significant recent flood was in March of 2010 when a slow moving storm dropped up to 10 inches of rain over three days. 

Image Source: NOAA 

Future Flooding:

In my last post, I mentioned the work by the Charles River Watershed Association and the Charles River Climate Compact to make plans for the projected 78% increase in participation over 50 years from Climate Change. The following map is a model for what flooring for a 10 year storm could look like by the year 2070. The darker blue areas represent water levels 8 feet and above normal.

Image Source: Charles River Watershed Association

This map was created by the compact and is the first step for planning ways to mitigate the impacts of severe weather. You can find the Model HERE. I encourage anyone interested to take a look and model various storms. You are able to model past storms such as Hurricane Ida and map out public utilities and critical services.

Features of the Charles!

Although, Boston is the first thought most have at the mention of the Charles River, there is a lot more than just the city! Here are some of the features of the watershed.