Baccharis Consulting LLC

Water Inundation in Broad Dyke Watershed, Delaware (2002-2017)

Picture of Broad Dyke Marsh

                                                           Broad Dyke Marsh

Discussion of Broad Dyke Watershed

Broad Dyke watershed is situated south of Christina River and north of Army Creek draining a mostly industrial and residential area.  A number of dikes, which restrict tidal flow and create impoundments, are present.  More information on the watershed can be found at this link.

This watershed has tidal exposure on the edge of Delaware River.  But like others discussed previously, it is a riverine watershed.  This means that precipitation events have an outsize influence on the inundation numbers.  For instance, you can have a heavy rainfall event in the upper Delaware River or its tributaries, the water will then flow into the main stem of the Delaware 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.  However, in the case of the Delaware River, the effects are not as extreme because of the greater surface area.

Broad Dyke Water Inundation (2002-2017)

 

Table 1. Broad Dyke Watershed Tidal Water (2002-2017) in acres
Year ETRW ECOW Total Tidal Water
2002 0.04 64.58 64.62
2007 0.04 75.38 75.42
2012 0.04 75.56 75.6
2017 0.04 82.70 82.74

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

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

Table 1 shows the amount of tidal water in the watershed has risen consistently since 2002.  The largest increase occurred in the 2002-2007 period and the smallest in the 2007-2012 period.  This trend is very similar to that seen in other upper Delaware River watersheds.

Table 2. Average Rate of Broad Dyke Watershed Water Inundation

(2002-2017) in acres/year

 Period  Average Rate (acres/year)
2002-2007 +2.16
2007-2012 +0.04
2012-2017 +1.43

Table 2 shows the water inundation rate was highest in the 2002-2007 period and has oscillated over time.  The 2007-2012 period shows the 2007-2012 slowdown seen in a lot of other watersheds.  The rise returned in the 2012-2017 period but not up to the 2002-2007 levels.

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