A StreamStats migration on February 18 fixed a number of minor bug issues and incorporated the following major updates for New Jersey, Delaware, and South Carolina StreamStats applications
New Jersey StreamStats Update
New Jersey StreamStats database has been updated with improved base elevation information and stream centerlines. Prior to the update it was based on 10-meter resolution elevation data and 24K-based hydrography. It is now based on 10-foot resolution data and 2,400 scale hydrography. In both cases, this is the best resolution/scale of any StreamStats state-wide project to date. New functionality was also developed to provide average watershed land slope based on the lag method in addition to 10-85 channel slope.
With this accuracy, New Jersey StreamStats can be used for watershed analyses to much smaller basins than what was previously possible for the New Jersey StreamStats application. It has a tighter fit with elevations along the channels to support future automated floodplain, bankfull, and culvert analyses. More accurate river morphology analyses could also be considered with this level of detail.
StreamStats for New Jersey can be used to estimate instantaneous flood discharges and monthly flow-duration and monthly low-flow frequency statistics for ungaged streams. All peak and low flow equations have remained the same for this StreamStats update. Streamflow statistics and basin characteristics produced by this version may deviate slightly from those generated previously. These deviations were not found to differ significantly among state regions and were distributed normally. Work has begun to develop new statewide equations to estimate flood discharges. These are planned to be integrated into New Jersey StreamStats when available.
Delaware StreamStats Update
The Delaware StreamStats database has been updated with improved base elevation information, stream centerlines, and flow estimates for many gaged locations that include 10 additional years of annual peak flow data and 20 additional years of annual low flow data as compared to prior reports. Prior to the update the database was based on 10-meter resolution elevation data and 24,000-based hydrography. It is now based on 3-meter resolution data and revised 24,000 scale hydrography. With this accuracy, Delaware StreamStats can be used for watershed analysis to much smaller basins than was possible using the prior Delaware StreamStats application.
StreamStats for Delaware can be used to estimate the magnitude of (1) peak flows for return periods ranging from 2 to 500 years (50-percent to 0.2-percent annual-exceedance probability), and (2) the magnitude of low flows as applied to 7-, 14-, and 30-consecutive day low-flow periods with recurrence intervals of 2, 10, and 20 years (50-, 10-, and 5-percent annual non-exceedance probabilities) for ungaged streams. Peak and low flow equations retain similar variables as used in the prior StreamStats database, though equation coefficients and regional skew values have been updated. Streamflow statistics and basin characteristics produced by this version may deviate slightly from those generated previously due to the finer spatial resolution of watershed delineations and additional years of record used to develop the regional equations. The updated application serves as the best source of peak and low flow estimates in ungaged areas of Delaware and the updated database may be used as a starting point for future studies looking to develop regression equations specifically for urban areas or to implement non-regression methods for ungaged peak and low flow prediction.
South Carolina StreamStats Update
South Carolina StreamStats added map layers for dams and roadways. With the addition of dams map layers, users can now evaluate the percent of the basin regulated by reservoirs included in the National Inventory of Dams similar to functionality available in Montana and Colorado. This functionality is available to all states who provide the map layers and delineations for dams.