APPENDIX 1 - GLOSSARY

Backwater -

• A water surface raised compared with natural depth. (NGH) (MARFC)
• A water surface raised compared with natural depth as a result of higher water downstream. (MARFC)

Backwater Floods - 

• were used in this project that included ice jams or backwater as a result of higher water downstream. (NGH)

Bankfull Stages - 

• Stage at which a stream just overflows its natural bank. (IGH)

Caution Stage -

•  A near-bankfull, but below flood stage at which some form of action must be taken.  This varies by location, but often involves actions such as closing roads and increasing staffing of emergency management agencies and public works departments. (MARFC)

CFS, Cubic Feet per Second - 

• Standard unit of stream flow. (MARFC)

Continuous Record Station - 

• is a station where streamflow and/or water-quality data are collected systematically over a period of years for use in hydrologic analyses. Data may be collected continuously or periodically. (USGS)

Creek - 

• Natural stream of water, normally smaller than, and often tributary to a river. (W) (IGH)

Datum Level - 

• A horizontal surface used as a reference to which elevations are related. (IGH) See also Gauge Datum. (NGH)

Drainage Basin - 

• The whole area having a common outlet for its surface runoff. (GGT) (IGH)
• Is part of the surface of the earth that is occupied by a drainage system, which consists of a surface stream or a body of impounded surface water together with all tributary surface streams and bodies of impounded surface water.(USGS)

Datum Level - 

• A horizontal surface used as a reference to which elevations are related. (IGH)

Flood Crest - 

• Highest (peak) elevation of the water level during a flood in a channel. (IGH)

Flood Frequency - 

• Number of times a flood above a given discharge or stage is likely to occur over a given number of years. (NGH)

Flooding - 

• Overflowing by water of the normal confines of a stream or other body of water, or accumulation of water by drainage over areas which are not normally submerged. (WMO)

Flood Peak - 

• The maximum rate of flow attained at a given point during a flood event. (NGH)

Floods Per Year - 

• Floods per year = total floods divided by total years. (MARFC)

Flood Stage - 

• Overflowing by water of the normal confines of a stream or other body of water, or accumulation of water by drainage over areas, which are not normally submerged. (WMO)

Gauge - 

• Instrument to measure water level. (NGH)

Gauge Datum - 

• Elevation of the zero of a gauge referred to a certain datum level. (TR) (IGH)

Gage Height - (G.H.) 

• Is the water-surface elevation referred to some arbitrary gage datum. Gage height is often used interchangeably with the more general term "stage," although gage height is more appropriate when used with a reading on a gage. (USGS)

Gauging Station - 

• is a particular site on a stream, canal, lake, or reservoir where systematic observations of hydrologic data are obtained. (USGS)

Ice Jam - 

• An accumulation of ice floes, brash ice and/or ice slush packed together. In a river the jam chokes the stream channel and causes a rise of the water level upstream from the jam. (NGH)

Period of record - 

• based on when gage became continuous recorder, present datum site, elevation and heights being the same. This is not the same as Water years from (USGS, CHOW, IGH) or hydrologic year from (IGH). The period of record we used for this project was based on:

1. Datum change - Last elevation and/or location change of water recording gage. (NGH)
2. Continuous recording gages - Starting period began when gages became USGS continuous 24 hour recorders.
3. Dam influences - Starting period began after completion of dam if needed. (NGH)
4. Urbanization - This had little effect on this project due to insufficient data.

Thus floods couldhave increased or decreased due to developments or increased run off. (NGH)

Return Period - 

• is the average time interval of a hydrologic event of a given or greater magnitude, usually expressed in years. May also be called recurrence interval. Can also be be expressed in terms of exceedance probability, which is the probability of the above event occurring in any given year. (USGS)
  • Return period for our use was the time period between flood events with at least 20 years of flood information.
    Return period = total years divided by total floods. In our case, return period is basically average time between floods. (MARFC)

Reservoir - 

• A body of water, either natural or artificial, used for storage, regulation and control of water. (IGH)

SFD, Second Foot Day -

• The volume of water represented by a flow of one cubic foot per second (cfs) for 24 hours; equal to 86,400 cubic feet. (WGRFC)

Site - 

• We used points based on points that MARFC forecast for, USGS info and gages that had continuous recording information. (Except Bainbridge) (MARFC)

Staff Gauge - 

• Graduated scale used to indicate the height of the water surface in a stream channel, reservoir, lake, etc. (NGH)

Stage - 

• Elevation of the water surface of a stream, lake, etc. relative to a datum. (NGH)

Stream -

1. Water flowing in an open or closed conduit.
2. A jet of water issuing from an orifice, or a body of flowing groundwater. (IGH)

Streamflow - 

• is the discharge that occurs in a natural channel. Although the term "discharge" can be applied to the flow of a canal, the word "streamflow" uniquely describes the discharge in a surface stream course. The term "streamflow" is more general than "runoff" as streamflow may be applied to discharge whether or not it is affected be diversion or regulation. (USGS)
• Volume of fluid flowing through a cross section of a stream per unit time. (NGH)

Stream flow floods - 

• were used when flood stage heights were questionable due to insufficient datum records. We used equivalent streamflow to flood stage exceedance. (MARFC)

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