Baccharis Consulting LLC

Water Inundation in Christina River Watershed, Delaware (2002-2017)

 

Picture of the Christina River

     Christina River at the Churchman’s Road crossing in New Castle County, Delaware

 

Discussion of Christina River Watershed

The Christina River along with its tributaries, Brandywine Creek and White Clay Creek, drain the largest Piedmont area in Delaware.  The tables below just show water inundation in the main stem of the Christina River.  Brandywine Creek and White Clay Creek are discussed separately.  The lower watershed is developed in the City of Wilmington while the upper tidal sections towards Christiana are more natural.  The upper tidal limit on the river reaches to the Smalleys Lake dam.  More information on the watershed can be found at this link.

Compared to previous watersheds discussed, this watershed has a large tidal exposure.  But like the others, it is a riverine watershed.  This means that precipitation events have an outsize influence on inundation numbers.  For instance, you can have a heavy rainfall event in the upper Christina River or its tributaries, the water will then flow into the main stem of the Christina River causing it to rise.  There is not enough area for the water to spread out.  In these watersheds (riverine) it is best to look at the trends rather than the actual numbers.

Christina River Water Inundation

(2002-2017)

 

Table 1. Christina River Watershed Tidal Water (2002-2017) in acres
Year ETRW ECOW Total Tidal Water
2002 144.92 761.69 906.61
2007 170.20 788.47 958.67
2012 181.95 797.19 979.14
2017 181.12 803.17 984.29

ETRW = Estuarine Tidal Riverine Water (Salinity < 0.5 ppt)

ECOW = Estuarine Coastal Oligohaline Water (Salinity 0.5-5 ppt)

Table 1 shows that the amount of tidal water in the watershed has risen consistently since 2002 but has also consistently slowed over time.   The largest increase occurred in the 2002-2007 period and the smallest in the 2012-2017 period.  This is likely due to the steep sides of the watershed.  During the 2002-2007 period, the lowest part of the watershed was flooded leaving the higher ground to be flooded.  Most flooding has occurred in the Churchmans Marsh and south of I-95 from Churchmans Marsh to roughly the I-95/I-295 split.

Table 2. Average Rate of Christina River Watershed Tidal Water Inundation 

(2002-2017) in acres/year

 Period  Average Rate (acres/year)
2002-2007 +10.41
2007-2012 +4.09
2012-2017 +1.03

Table 2 shows that the water inundation rate was highest in the 2002-2007 period, but has consistently slowed over time.

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