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Physical Monitoring

Stream Channel Surveying

A stream channel geomorphic survey measures the shape, slope, and bed composition of a stream channel, usually over time to track changes.

The surveys conducted by Montgomery County consist of the following:

  • Longitudinal profile

A survey of the stream bed elevation along the thalweg, or deepest point in the stream.

  • Cross-sectional profile(s)

A survey at a specific cross-section along the stream channel.

  • Pebble counts

Provide information on particle size distribution of the stream bed.

  • Measures of sinuosity (curvedness)

Some streams flow straight, while others make numerous winding curves.  The sinuosity ratio is the distance between two points on the stream measured along the channel divided by the straight line distance between the two points.  Also known as the changing curve of a stream.

 

Why is Stream Channel Surveying Important?

Geomorphology surveying allows us to depict how the stream channel changes (or remains stable) in response to natural and human-caused influences. Repeated measurements at a specific study area allow for direct comparison of the features of the stream channel over an extended period of time.

Image of stream flow monitoring

longitudinal profile depicts the down slope gradient of the stream. Measurements of the longitudinal profile taken over time can document trends in aggradation (sediment build-up) or degradation (erosion). Looking at these trends, we can see how disturbances such as floods or increased sediment inputs from land-use modify the channel bed.

The longitudinal profile also shows features such as riffles, runs, and pools. Typically, biological diversity is greatest when a variety of feature types are present (i.e., a combination of riffles, runs, and pools).

Longitudinal profiles, in combination with cross-sectional profiles, are useful in determining the vertical dimension of channel features. Over time, repeated surveys show how the stream channel adjusts (horizontally and vertically) to accommodate the various flows it handles.

Channel sinuosity is important because it reflects the stream's adjustment of its slope to the valley slope. The more sinuous (curvey) a stream is, the more gentle the valley slope.

Pebble counts can show shifts in stream bed material composition over time. For example, a stream may go from having mostly large, cobble size particles, to having mostly sand and gravel size particles as the stream aggrades (fills in).

 

Stream Channel Surveying Activities

The Montgomery County Department of Environmental Protection (DEP) conducts annual geomorphic surveys at 17 separate areas to assess stream channel characteristics. The surveys are performed as part of the requirements for the state NPDES permit. They provide an effective tool for tracking changes to the stream channel that result from natural occurrences and changes in land use; both of which can have profound effects on the stream.

Most of the study efforts to date have focused on the Clarksburg Special Protection Area since it offers the County a unique opportunity to observe changes in the morphology of the stream channel in response to surrounding land use changes. What we learn from indepth study in the Clarksburg SPA will be applied elsewhere in the County as we set the standard for future development requirements to mitigate environmental impacts.

 

Image of DEP staff member performing a stream channel survey.Data and Data Requests

DEP stream channel survey data is entered into data forms, which log information on the following worksheets:

  • Introduction: information about the spreadsheet.

  • Summary: information about the study reach (name, date, location, drainage area, etc.)

  • Profile: longitudinal slope profile.

  • Pattern: calculation of sinuosity.

  • Materials:channel bed materials (pebble count information).

  • Dimension: cross-sections.

 

If you are interested in obtaining data or protocols, please contact DEP at askdep@montgomerycountymd.gov. In your request, please provide the following information:

  • Name, organization (if applicable), phone number, and/or email address

  • Type of data requested

  • Time frame requested

  • Explanation for use of data (helps to personalize the data request)

  • Preferred method of data retrieval (email, CD by mail, FTP, pick up CD or materials from DEP offices)

 

Looking for more DEP data?  Visit our Biological Monitoring data page to view all the biological monitoring data sets available to the public.

 

Additional Resources

Spreadsheet Tools for River Evaluation, Assessment and Monitoring from Ohio Department of Natural Resource Modules

Stream Flow Monitoring

Monitoring of stream flow is a critical component in the assessment of stream structure and stream quality. Stream flow data can be used to:

  • Enhance public safety through forecasting and managing floods

  • Delineate floodplains

  • Determine water quality conditions

  • Compute loads of sediment or nutrients being carried downstream

  • Design reservoirs, bridges, and culverts

  • Compare to rainfall data to depict stream response to local storm events

Stream Flow Monitoring Activities

The Montgomery County Department of Environmental Protection (DEP) and the U.S. Geological Survey (USGS) are working cooperatively to monitor stream flow continuously at numerous stations in Montgomery County, Maryland. These stations include:

Photo of a man standing next to a stream gage.
  • Five stations in the Clarksburg Special Protection Area (2004 to present) to monitor hydrologic changes that occur from changes in land use

  • One station in the Northwest Branch of the Anacostia River near Colesville, Maryland (1997 to present) to monitor urban flooding issues and hydrology associated with watershed restoration efforts

  • Two stations on Turkey Branch and Good Hope Tributary (2007 to present) to monitor stream restoration efforts in the headwaters of the Rock Creek and Anacostia watersheds

  • One station on Sligo Creek near Takoma Park (October 2008 to present) to monitor stream flow. (The County has a long-term goal of establishing a water-quality monitoring program at the Sligo Creek station (if funded) as part of its efforts to reduce pollutant loads in the Anacostia River watershed—including loads from nutrients, sediment, fecal colliform, and trash.)

 

The following tasks are typically handled during service visits to stream flow-gage stations by USGS hydrologic technicians and/or Montgomery County water quality specialists:

  • Checking data recorder operation and gage height relative to the outside reference gage

  • Replacement of batteries

  • Clearing of sediment or debris from the orifice and purge orifice lines

  • Checking and servicing crest-stage gage(s)

  • Inspecting the control conditions and removing any leaves, debris, or trash that may be causing backwater at the station

Photo of a stream gage.
 
Sopers Branch Stream Gage (USGS Station with real-time data available from the USGS National Water Information System).

 

Stream flow data is collected through the stream gages as well as through use of a hand-held velocimeter. The stream gage records the stage, or the height of the water surface above a known elevation, such as sea-level or the gage station. Measurements of the area and velocity of the stream are used to calculate volume passing a particular point in a certain amount of time, or discharge (usually measured in cfs, or cubic feet per second).

After enough measurements of the stage and the discharge are collected, a correlation between the two begins to emerge. This is known as the stage-discharge relationship, and when plotted on a graph it is called a rating curve. It provides a useful tool for land-use planners, engineers, and other interested parties to evaluate stream flow conditions. Since the stage-discharge relationship can change over time, an ongoing record of gage height and discharge data (with mean daily flows and yearly flow statistics) is kept by USGS, along with a record of datum corrections and rating shifts that are required to maintain an accurate stage-discharge relationship. The daily values are published in the USGS Annual Water-Data Report.

The stream flow gages collect a continuous record of gage heights (in 5 minute to 15 minute intervals) by use of a non-submersible pressure transducer system that is interfaced with a Data Collection Platform (DCP). The data is transmitted using a satellite or phone modem in near real-time to the USGS Maryland-Delaware-DC Water Science Center.

Looking for more DEP data?  Visit our Biological Monitoring data page to view all the biological monitoring data sets available to the public.

 

 

Map of Stream Gage Locations

Map of stream gage locations.

Locations of USGS Stream Gages. These gages have USGS site identification numbers. You can access real time flow data from these gages using the USGS National Water Information System Web interface

Additional Resources

 

Temperature Monitoring

All aquatic organisms have an optimal range of temperature under which they can successfully maintain populations. Some species may be able to tolerate higher than optimal temperatures and survive, but they will not thrive. For example, brown trout can tolerate temperatures above 68 °F (20 °C) indefinitely, but they would not be successful reproducing.

Maryland classifies its waterbodies into Use Classes. Each Use Class has an associated range of species and species function (e.g., adult brown trout survival, or brown trout reproduction). Acceptable temperature ranges are defined so that these species can survive in their particular Use Class.

  • Class IV Waters

Use Class IV waters are waters that brown trout can survive in but not reproduce in, hence Use Class IV waters are meant to designate waters that can support a fishery where the brown trout populations are maintained by periodic stocking. An example of Use Class IV waters are portions of Northwest Branch and Upper Rock Creek. Maryland sets a maximum threshold water temperature of 75 °F (24 °C) for Use Class IV waters.

  • Class III Waters

Class III waters includes waterbodies where brown trout can reproduce. An example of a Class III water in Montgomery County is Paint Branch. The maximum water temperatures does not usually exceed 68 °F (20 °C). Brown trout are able to reproduce here and stocking is usually not necessary to maintain populations with proper regulations in place (e.g., catch and release fishery).

  • Class I Waters

Use Class I waters include all other freshwaters of the state where a maximum temperature of 90 °F (32 °C) should not be exceeded.

 

What about Class II?    Class II is reserved for brackish water and does not apply to Montgomery County streams. 

 

Image of DEP sampling a stream.In nearly all cases, the concern regarding water temperature is when it gets too high or exceeds the maximum value set for a particular use class. (Not how low water temperature gets.) Temperature spikes are often associated with discharges of rainwater runoff from areas with high imperviousness (surfaces where water cannot soak into the ground, such as roads and parking lots). Furthermore, discharges from improperly designed stormwater management ponds can cause high temperature spikes. The cumulative effects of these temperature spikes can harm the overall health of aquatic communities.

Learn more about Use Classes in Montgomery County  (PDF, 2.5Mb)

 

Temperature Monitoring Activities

Given that the concern with temperature monitoring are high temperatures rather than low ones, stream temperatures are monitored from May 31 to September 30, when temperatures are highest. Temperature loggers are placed in specific stream sites during May, and are recovered in October. Loggers are set to record the maximum temperature within a 24 minute period continuously during the time period specified.

DEP monitors temperatures at targeted stream sites where land uses are expected to raise water temperatures (such as in areas that are under construction). Special Protection Areas (SPA) are also subjected to concentrated temperature monitoring. Temperature meters are deployed at specific sites to assess the ability of stormwater or sediment and erosion control devices and systems (otherwise known as Best Management Practices or BMPs) to minimize thermal impacts.

Typically, a temperature logger is placed in the stream, both upstream and downstream of the discharge channel from the BMP. Generally, the temperature of the stream and the water discharging from the BMP is monitored by a consultant hired by the developer.

 

Data and Data Requests

Montgomery County has collected instream temperature data from 1995 to the present. However, the sites selected for temperature monitoring would not be available for every year since 1995. Tables and maps are available showing the locations where temperature was monitored during specific years. Maps can be made to order depending on the request.

Temperature Data Table
Field Name Description
Station The station field is a nine character code that identifies the station name. The stations are a combination of the two letter code for the watershed+the two letter code for the subwatershed + the single digit stream order code+ the sequential reach number.
Date The date and time the water temperature was recorded.
Temperature Water temperature in Celsius.

 

Data Constraints

For proper interpretation, water temperature data should be compared with air temperature and precipitation data from the same time period.

 

Submitting a Data Request

If you are interested in obtaining data or protocols, please contact DEP at askdep@montgomerycountymd.gov. In your request, please provide the following information:

  • Name, organization (if applicable), phone number, and/or email address

  • Type of data requested

  • Time frame requested

  • Explanation for use of data (helps to personalize the data request)

  • Preferred method of data retrieval (email, CD by mail, FTP, pick up CD or materials from DEP offices)

 

Looking for more DEP data?  Visit our Biological Monitoring data page to view all the biological monitoring data sets available to the public.

 

Precipitation Monitoring

Many stream flow and hydrologic relationships are based on precipitation levels. DEP measures precipitation to properly characterize rain events and relate them to the stream flow response.

DEP maintains two rain gages— both of which are located within the Clarksburg SPA (one in Black Hills Regional Park and one in Little Bennett Regional Park). DEP is investigating re-installing gages in the Paint Branch and Piney Branch SPAs.

Image of DEP staff studying a stream.

 

Data and Data Requests

Available Data

DEP has precipitation data for Little Bennett rain gage from 2003 - present, and Black Hills from 2004 - present.

Precipitation data are usually downloaded quarterly, converted to standard time as needed, and compiled by year into Excel spreadsheets for both Little Bennett and Black Hills. Each spreadsheet has worksheets for each quarter of the year, with a Date/Time column and a Rain (in inches) column.

 

Submitting a Data Request

If you are interested in obtaining data or protocols, please contact DEP at askdep@montgomerycountymd.gov. In your request, please provide the following information:

  • Name, organization (if applicable), phone number, and/or email address

  • Type of data requested

  • Time frame requested

  • Explanation for use of data (helps to personalize the data request)

  • Preferred method of data retrieval (email, CD by mail, FTP, pick up CD or materials from DEP offices)

Looking for more DEP data?  Visit our Biological Monitoring data page to view all the biological monitoring data sets available to the public.