A-9 



mately 25-30 percent is derived from construction sites in the metropolitan 

 region. Inasmuch as population can be expected to continue to burgeon in 

 many areas surrounding the Chesapeake Bay, construction activities can 

 also be expected to increase. This in turn will transform the landscape 

 and may lead to the addition of uncontrolled quantities of silt to the 

 estuarine tributaries (State of Maryland, 1968) . 



Shoreline erosion also contributes to the silt load and is the 

 single most dramatic, and most readily apparent geomorphological process 

 occurring in the Bay. Historical data, though somewhat spotty, provides 

 some perspective. It has been estimated that, along the 230 miles of 

 Maryland's primary Bay shoreline, some 6,000 acres of land have been 

 lost to the sea between 1845 and 1942. Recent rates of erosion loss are 

 estimated to be approximately 0.17 acres/mile/year in the northern Bay 

 area and 0.34 acres/mile/year in Maryland's southern Bay portion. To 

 illustrate the variability of erosion loss rates estimated between 1845 

 and 1942, the Cecil-Somerset County shoreline losses were estimated to 

 be 0.13 acres/mile/year, while Dorchester County losses were estimated 

 to be of the order of 0.64 acres/mile/year. It must be emphasized that 

 land area losses do not indicate volumes of material handled, because 

 of the differential in land elevation of various areas of Bay frontage. 



The present and anticipated future social and economic development 

 of the Chesapeake Bay Basin, with the estimated large increase in popu- 

 lation, emphasizes the vulnerability of the Bay's sensitive estuarine 

 system to the future works of man. In particular, the waste discharges 

 of man's commerce and activity have a growing impact on the Bay. These 

 waste loads are derived from municipal, industrial and agricultural 

 sources. 



Agricultural pollutants consist primarily of silt, fertilizer, 



insecticides, herbicides, and animal wastes. Industrial wastes contain 

 a wide assortment of detrimental material ranging from sand and gravel 

 wastes and heavy metals through complex chemical compounds and mine 

 waste. Many of the latter waste types are toxic to both aquatic biota 

 and man. Municipal discharges contain human wastes and a huge panorama 

 of household and industrial by-products, and often inject significant 

 bacterial loads into the aquatic environment, infecting both finfish 

 and shellfish, making them potentially dangerous and therefore unfit 

 for human comsumption. 



Gross estimates indicate that pollution affects some 400,000 acres 

 of finfish habitat and 42,000 acres of shellfish habitat in Chesapeake 

 Bay. Municipal and domestic discharges cause the major pollution 

 problem. 



There are other significant threats to the Chesapeake Bay 

 environment. These include both inter- and intra-basin diversions 



