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Geo Lab Final Vocab
| Question | Answer |
|---|---|
| (average depth method) | Q = A x V A: cross-sectional area of stream V: average stream velocity |
| (area method) | Q = W x D x V Q: average discharge (in dimensions of volume/time) W: average width of the stream (cm) D: average depth (cm) V: average stream velocity (cm) |
| average surface velocity | d/t d: distance traveled (cm) t: time of travel (seconds) |
| average stream velocity (cm/sec) | (d/t) x 0.85 d/t: average surface velocity |
| cross-sectional area of stream (cm) | #shaded blocks x area one block represents (cm2) |
| recurrence interval | (n + 1) / m n: # years of data m: rank |
| Headwaters | higher elevations; erosive |
| Main stem | middle elevations; channel stores and removes sediment |
| Delta | at base level; lowest elevation; depositional |
| Meandering streams | formed by high sediment loads and low gradients. |
| Braided Streams | formed with high sediment loads at high gradients. |
| base level | the lowest elevation to which the stream can erode its channel. Affected by sea level and tectonic uplift. |
| sediment load | bed, suspended, and dissolved |
| Bed load | coarser and denser particles that remain on the bed most of the time but move by saltation |
| Suspended load | finer particles that are carried along in the main part of the stream |
| Dissolved load | ions in the water as a result of chemical weathering of rocks |
| gradient | slope of a stream (rise/run). Measured in m/km, m/m, ft/ft. |
| Velocity | the rate at which water moves. Gradient (slope) and volume (rainfall) affect velocity. Measured in m/s, cm/s |
| Discharge | the amount (or volume) of water passing a given point during a specific time interval. Measured in m3/sec, cm3/sec |
| watershed | A region that collects water that feeds into a given drainage network. The watershed divides are high areas which separate adjacent watersheds. |
| probability | percent chance of seeing any given interval in a certain year |
| recurrence interval | the average time in years between successive peak discharges |
| base flow | average flow of the river during the course of the year |
| peak discharge | river flow reaches the tops of the natural levees |
| flood | river flow overflows the natural levees onto the floodplain |
| bank full stage | highest discharge per year – not necessarily a flood event |
| infiltration | when melted snow and rain seep through the ground through pores in sediments or fractures in rock |
| recharge | the rate at which the volume of water in an aquifer rises over time |
| aquifer (water table) | Water table is re-supplied by rain as it recharges the aquifer. Crystalline rocks like granite can make good aquifers if they are highly fractured (fractures are secondary porosity). Permeable rock bodies. Includes materials such as gravel, sands |
| aquifer (confined) | formed wherever water infiltrates a permeable rock or soil that is bordered by aquicludes. They are under pressure, and water in wells drilled into this aquifer will rise in he well pipe to a level above the upper aquiclude. |
| aquiclude | impermeable/confining layers (with a hydraulic conductivity of 10-9 m/sec or less) are hydraulic barriers that slow or impede water’s movement. May be composed of clay, shale, and massive nonfractured igneous and metamorphic rocks. |
| zone of aeration | place in an unconfined aquifer, above the water table; moist soil and sediment, where pores contain both air and water. |
| zone of saturation | place in an unconfined aquifer where pore spaces completely filled with water |
| water pressure surface (or potentiometric surface) | the level above the upper aquiclude |
| artesian well | well drilled into a confined aquifer |
| water table | boundary between saturated and unsaturated zones |
| porosity | the volume of void space per total volume of voids and sediment. Measured as a percentage (%) or decimal less than 1 (0.00001 – 0.99). (High in silt, low in sand) |
| permeability | rate at which water will pass through a given volume of sediment. Tells how well-connected pore spaces are. |
| Topography | geographic elevation of each point a.s.l. |
| lake level | elevation of lake surface (usually top of water table) |
| unsaturated zone | everything above the water table (up to land surface) |
| water table | everything between the aquiclude the top of the water table |
| water table aquifer | pretty much the same as the water table |
| aquiclude | everything under the confining unit (starting with top of confining unit) |
| Yorktown Fm. | younger, serves as aquifer |
| Eastover Fm. | older, serves as aquiclude |
| Construction setback and moveback (move houses off the beach) Advantage | reduces threat of destruction of property; allows natural shore processes to operate; no impact on marine biota |
| Construction setback and moveback (move houses off the beach) Disadvantage | does not halt erosion; area must be available for relocation; may reduce views |
| Natural Vegetation (aquatic grasses, dune grasses, etc.) Advantage | dampens waves and binds soils; reduces soil creep and rain-wash; no impact on marine biota |
| Natural Vegetation (aquatic grasses, dune grasses, etc.) Disadvantage | easily damaged by wave action; may have to be frequently replanted; limits access and recreational use of beach |
| Beach nourishment (add sand to the beach i.e. Virginia Beach) Advantage | beach is suitable for use; does not have a negative impact on downdrift shoreline |
| Beach nourishment (add sand to the beach i.e. Virginia Beach) Disadvantage | does not halt erosion; has to be periodically renourished; affects biota |
| Bulkheads or seawalls (along the shoreline usually with rocks or concrete) Advantage | shields the land from wave attack and erosion; low maintenance and costs |
| Bulkheads or seawalls (along the shoreline usually with rocks or concrete) Disadvantage | limits access and recreational use of beach and scenic value; may cause loss of adjacent beach; affects biota |
| Revetment or breakwater (structure offshore parallel to beach) Advantage | shields the land from erosion and reduces wave reflection; very durable |
| Revetment or breakwater (structure offshore parallel to beach) Disadvantage | limits recreational use of beach and scenic value; may cause loss of adjacent beach; affects biota |
| Groyne (one wall perpendicular to shore)/Jetty (a double groyne) Advantage | builds beach on updrift side |
| Groyne (one wall perpendicular to shore)/Jetty (a double groyne) Disadvantage | downdrift shoreline may erode; beach nourishment may be needed; affects biota |
| Estuary | The wide section of a river channel where it nears the sea, characterized by a mix of salt and fresh water |
| microtidal estuary | An estuary where tidal currents approach 1 m/s and has a tidal range less than 2 meters |
| magnitude | velocity as a function of m/s |
| spring tide | an exceptionally high or low tide that occurs when there is a full moon or new moon |
| neap tide | A tide that occurs when the difference between high and low tide is least; the lowest level of high tide. Neap tide comes twice a month, in the first and third quarters of the moon |
| flood tide | incoming or rising tide. |
| ebb tide | outgoing or receding tide. |
| What is mean total discharge for York River Estuary from all sources? | 71 m3/sec |
| What is the total influx of sediment into the York River estuary? What type of sediment is it? | 400,000 tons/year; Mud. Note: sand makes up shoals. |
| How did you get hydraulic conductivity for both geologic formations? | Look up the hydraulic conductivity on the chart (based on what kind of material you drilled into), look up the range of HC (in m/sec) and pick the lowest value in the range. Then convert that to m/day (86,400 sec/day) and record answer. |
| How did you determine topographic elevations and total head? | Go to the Well Gauging Form and subtract the “height of well above ground” from the “well lip elevation” to get the topographic elevation at each well location. Using a pen, write the topography elevation next to each well location. |
| How did you draw groundwater contour maps? | Measure depth to groundwater in several wells. On the “Well Gauging Form/Boathouse Well Field,” enter depth to water that gets measured in each well. LL refers to lake level, which is a surface water measurement. Calculate total head |
| Know the description of the Moore House member of the Yorktown Formation. | The youngest member, Moore House, is described as an “orange fragmental shell hash, extremely calcareous but containing some fine quartz fragments” overlying “tan clayey highly calcareous sand containing abundant mollusks.” |
| LCBS | Large Cross-bedded Biofragmental Sand |
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