The Jabez Branch: A Unique and Fragile Coastal Plain Stream

The Jabez Branch is a tributary to Severn Run and is the only stream in the Maryland Coastal Plain physiographic region that supports a native, self-sustaining brook trout population.

History

Brook trout were first discovered in the Jabez Branch in 1977 upstream of Route 32. Since then Maryland Department of Natural Resources (DNR) biologists have conducted periodic electrofishing surveys of the entire length of the stream and have discovered brook trout population throughout nearly the entire Jabez Branch stream network. The highest density of brook trout has been consistently recorded in tie Left Fork.

In 1987, routine surveys by DNR fisheries personnel discovered that a severe decline in trout population had occurred. Further investigation revealed that construction of I97 had created a basin in the median of north bound/south bound Route 3 lanes which were being used as a sediment and stormwater management basin. As runoff collected in the one acre basin and warmed up, this solar heated water was being continuously discharged directly into the Left Fork. When the State Highway Administration was notified of the situation, the basin discharge source was permanently sealed. In hindsight it can be said, that was the beginning of demise of the Jabez Branch as a result of man induced activity.

Between July and October 1988 two continuously recording thermographs were placed in the Jabez Branch to monitor summer water temperatures. The gathered data indicated the stream experienced sharp temperature rises during periods of rain. The sharpest rise occurred in August when temperatures in the Left Fork rose from 63.5 to 73.4 degrees F (17.5 to 23 degrees C) within a sixty minute period following a one inch rainfall.

The brook trout population continued to decline and in December 1990, DNR biologists declared the trout extinct. Nevertheless, in 1991, DNR biologists attempted the first of three transplants of wild brook trout from other Maryland streams with introduction of 328 fish. By 1995, electofishing surveys indicated the brook trout population and reproduction rate to be back to close to previous numbers.

In 1991 the Jabez Branch was recognized by DNR as a Non-tidal Wetland of Special State Concern.

In 1997, 1,475 feet of dry stream channel in the headwaters of the Left Fork was restored using the Rosgen methodology. The purpose of the restoration was to reduce sediment loading as a result of stream channel erosion.

Brook Trout Habitat Requirements

It is believed the survival and reproduction of the trout especially in tie Left Fork is due to the thick canopy growth along the stream and the large number of cool underground springs that seep visibly year round into the stream. With water temperatures averaging 55 degrees F, this section of tie stream was especially able to sustain cool enough temperatures despite the intermittent warm water flushes generated from stormwater runoff from nearby homes and roads. The I97 construction pushed the Left Fork's temperatures above brook trout upper tolerance limits. Brook trout are known to be least tolerant of all trout species to fluctuating temperatures and prefer temperatures in the range of 53.6 degrees to 60.8 degrees F (12 degrees to 16 degrees C) .

Generally speaking brook trout require:

1. Cool stream temperatures year round
2. Good water quality
3. Deep pools
4. Gravel stream beds
5. Dense forested buffers

Land Uses

Approximately 120 acres of the Jabez Branch watershed is within the Severn Run Natural Environmental Area. Anne Arundel County has also purchased conservation easements on an additional 49 acres abutting the Left and Right Forks. State Highway Administration also owns approximately 100 acres of undeveloped woodland considered as excess property. Attempts by the Severn River Commission to persuade SHA to transfer the property to a conservation trust or place conservation easements on the land have not been successful.

In 1990 a DNR study documented that the Left Fork subwatershed was 50% forested and much of the remaining land was in agricultural use. Less than 4% imperiousness characterized that subwatershed.

The majority of the approximately 1,500 acres of the Jabez Branch watershed is zoned RLD and RA. It is not known what zoning changes will be adopted as a result of the recommendations of the Odenton Small Area Planning Committee.

Summary

The Jabez Branch is a unique resource that has already reached its stress limit. By all indications, the stresses are man induced and the historical data highlights just how fragile this small stream system is.