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


Picture of the Upper Delaware River watershed

                                    Upper Delaware River at Fox Point State Park

Discussion of Upper Delaware River Watershed

Upper Delaware River watershed is situated on the Delaware River main stem from the Delaware/Pennsylvania state line to just upstream of Delaware Memorial Bridge.  Most of the watershed is water surface with a small number of shoreline edges, most of which are developed.  More information on the watershed can be found at this link.

This watershed has tidal exposure throughout but shows it on the landward edges.  But like other watersheds discussed previously, it is a riverine watershed, only larger.  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.

Upper Delaware River Water Inundation (2002-2017)


Table 1. Upper Delaware River Watershed Tidal Water (2002-2017) in acres
Year ETRW ECOW Total Tidal Water
2002 4.787.47 3.101.40 7,887.87
2007 4,795.40 3,099.31 7,894.71
2012 4,795.76 3,114.29 7,910.05
2017 4,792.69 3,123.53 7,916.22

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.  This could be due to the steep sides of the watershed.  The largest increase occurred in the 2007-2012 period and the smallest in the 2002-2007 period.  This is different than a lot of watersheds, which experienced a slowdown in the 2007-2012 period.  The difference could be due to precipitation factors.

Table 2. Average Rate of Upper Delaware River Watershed Tidal Water Inundation

(2002-2017) in acres/year

 Period  Average Rate (acres/year)
2002-2007 +1.17
2007-2012 +3.07
2012-2017 +1.24

Table 2 shows that the water inundation rate was highest in the 2007-2012 period and has oscillated over time.  Similar to Brandywine this watershed did not show the “2007-2012” slowdown in rise, instead, it rose faster.

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