Geology topics
Source-linked reports with geographic coverage including Delaware.
Seismic-reflection profiles indicate that during the Pleistocene the Delaware River flowed across the continental shelf east of Delaware Bay and emptied into Wilmington Submarine Canyon. The ancestral valley (width, 3 to 8 kilometers; relief, 10 to 30 meters) is buried, is not reflected in the surface topography, and probably predates the formation of the present canyon head.
As a result of continuous pumping since the 1890's, a regional cone of depression encompassing 363 km 2 has developed within the artesian Miocene Cheswold aquifer at Dover, Del. The aquifer is not being recharged significantly by leakage near the center of the cone, nor is major recharge induced in the updip subcrop area. The source of pumped water is apparently an area of about 65 km 2 northwest of Dover, where vertical leakage is substantial. This area was delineated by use of a digital aquifer model and streamflow data. A model of the unconfined aquifer was used to compute the unconfined aquifer's natural discharge to streams, assuming no leakage to underlying artesian aquifers. The area of substantial leakage to the underlying Cheswold was delineated as being coincident with that area where model-computed values of stream discharge were substantially larger than actual values of stream discharge determined in the field.
Trainer and Hunt (9) stated that lead poisoning of Canada geese ( Branta canadensis ) had been reported from three states: North Carolina, Indiana, and Wisconsin. More recently, the Mississippi Flyway Council (8) cited suspected cases of lead poisoning of Canada geese in Massachusetts, New York, Pennsylvania, Delaware, Virginia, and Maryland. Hanson and Smith (6) also cited cases in widely separated areas of the country, including Texas and Michigan. this paper reports lead poisoning among Canada geese in Delaware, and presents evidence that it is a recurring problem among wintering flocks of Canada geese along the Middle Atlantic Coast.
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The water chemistry of streams in the Delaware River basin falls into eight general groups, when mapped according to the prevalent dissolved-solids content and the predominant ions normally found in the water. The approximate regions representing each of these iso-chemical quality groups are shown on the accompanying base map of the drainage basin.
No abstract available.
This report presents an analysis and evaluation of the trend of the sediment yield for the Brandywine Creek at Wilmington, Del., for the period from December 1946 to September 1955. The interest in such an analysis and evaluation stems from the efforts of the Brandywine Valley Association and others to reduce erosion and improve land use in the watershed. The data used for the analysis were taken from the continuous suspended-sediment and water-discharge records of the stream at Wilmington and the precipitation records at 8 standard and 1 recording rain gages. The analysis was made on the basis of 123 storm events for this period of record using only the water and sediment discharge attributed to direct runoff. These data represent 89 percent of the total sediment discharge and 19 percent of the total water discharge. The sediment load for each of the storm runoff events was correlated with storm runoff, rainfall intensity, and season to remove the effect, if ant, of the variation caused by these factors. The evaluation of the relative trend of sediment yield was made by two methods; first, the accumulative graph pr double mass curve as a graphical method, and second, the rank correlation method which results in a numerical coefficient and its significant. The graphical method of this evaluation shows an approximate 38 percent decrease in sediment yield for the period 1952 to 1955 from that for the period 1947 to 1951. The rank correlation coefficient was 0.152 for the same analysis showing a very high level (almost 99 percent) of confidence in the significance of a decreasing trend. A parallel analysis to that above using "peakedness" instead of rainfall intensity as a measure of storm intensity was made because "peakedness" is easier to evaluate than rainfall intensity. The results of this analysis again indicates the probably decreasing trend of sediment yield as shown by the change in slope of the accumulative graph from 0.77 fir the 1947 to 1951 period to 1.05 for the 1952 to 1955 period or 28%, and by the rank correlation coefficient of 0.114 with a 94 percent level of confidence of a decreasing trend. Appendix A of this report shows a similar analysis by usede of monthly sediment discharge and "direct" runoff as determined for an analyses of runoff patterns. The results indicate only a small decreasing trend, if any, in sediment yield. This is probably due to the fact that the correlations with rainfall and season for adjusting these data were rather poor--indicating bias by unknown parameters that cannot be evaluated. Appendix B presents the methodology of using rank correlation to evaluate the trend of variate-values with respect to time with special reference to the trend of sediment yield from a watershed.
The purpose of this report is to summarize data on the use of water in the Delaware Basin Project area (fig. 2) and to list the principal data sources that are available in published form. The tables and bibliography will assist Geological Survey personnel assigned to the Delaware Basin Project in evaluating the scope and deficiencies of previous studies of the basin. Information is also given on the use of water by public supplies in the New York-New Jersey region comprising the New York City Metropolitan Area and in the remaining north-central and south-eastern parts of New Jersey. These regions may depend increasingly on water from the Delaware River basin for part of their public supplies. The Geological Survey has the responsibility for appraising and describing the water resources of the Nation as a guide to use, development, control, and conservation of these resources. Cooperative Federal-State water-resources investigations in the Delaware Basin States have been carried on the the Geological Survey for more than 50 years. In July 1956 the Survey began the "Delaware Basin Project," a hydrologic study of the Delaware River basin in order to: 1) Determine present status and trends in water availability, quality, and use, 2) assess and improve the adequacy of the Survey's basic water data program in the basin, 3) interpret and evaluate the water-resources data in terms of past and possible future water-use and land-use practices, and 4) disseminate promptly the results of this investigation for the benefit of all interested agencies and the general public. The Geological Survey is working closely with the U.S. Corps of Engineers and other cooperating Federal and State agencies in providing water data which will contribute to the present coordinated investigation aimed at developing a plan for long-range water development in the Delaware River basin. Estimates of quantities of water used are given for water withdrawn from streams and aquifers during calendar year 1955, as compiled or estimated from publications and manuscripts prepared between 1950 and 1956. All quantities are given in millions of gallons per day (mgd). The source of the water used, ground or surface, and the type of use to which is was put -- public supply, industrial supply, irrigation, or rural use -- is given. Use of water for hydroelectric power was not compiled for this report. Most tables in this report do not subdivide withdrawals into fresh and saline water; however, most supplies are fresh, except some of those withdrawn directly from the Delaware River downstream from Philadelphia, Pa. All quantities are expressed as an average rate for a full year and are lower, therefore, than rates resulting from the increased demand for water during the summer for air conditioning and supplemental irrigation. The primary emphasis of this study was to get an over-all picture of water use throughout large parts of the basin. Therefore, publications relating to a dingle city or county, other than New York City, seldom were used; revisions and refinement based on such sources of information are best made by the field personnel most familiar with locally filed publications and published data.
This investigation was undertaken to locate deposits of rock, sand, gravel, fill and borrow in northern New Castle County which may be potential sources of material for highway construction, and to prepare maps and descriptions of the surficial earth materials relative to their geologic and engineering properties.
A search for aquifers in an area immediately north of the Chesapeake and Delaware Canal in New Castle, Del., has been made by an electrical resistivity study. The search located 32 sites that may be underlain by sand and gravel. The thicker deposits are significant with respect to the occurrence of ground water, and all of them are of interest as possible sources of sand and gravel for construction purposes, such as for highway construction. The thickness of these deposits ranges from 4.4 feet to 77 feet, and the computed resistivity for these ranges from a low of 97,800 ohm-cms to a high of 423,800 ohm-cms. The study located with certainty one buried channel filled with sand and gravel deposits and pointed out the possibility of others that may be aquifers. The interpretations show that a large deposit of sand and gravel is present in the eastern part of the area investigated and it is tentatively assumed that this deposit is continuous and may yield large quantities of ground water. Places where the deposit was found to be the thickest and of high resistivity are described.
This report discusses the occurrence of ground water in relation to certain problems in highway construction and maintenance. These problems are: the subdrainage of roads; quicksand; the arrest of soil creep in road cuts; the construction of lower and larger culverts necessitated by the farm-drainage program; the prevention of failure of bridge abutments and retaining walls; and the water-cement ratio of sub-water-table concrete. Although the highway problems and suggested solutions are of general interest, they are considered with special reference to the State of Delaware, in relation to the geology of that State. The new technique of soil stabilization by electroosmosis is reviewed in the hope that it might find application here in road work and pile setting, field application by the Germans and Russians is reviewed.