Hurricane Harvey rainfall at 40 southeast Texas gauges

The highest observations came from Jefferson County

The USGS table gives 60.58 inches at Nederland 1.5 SW and 60.54 inches at Groves 1.3 N. The report identifies both as Jefferson County Drainage District gauges. Their difference is just 0.04 inches, while 11 stations in the table recorded more than 50 inches. Source 1 Source 2

The storm’s slow movement prolonged the rain

The National Hurricane Center’s post-storm analysis describes Harvey slowing after making landfall, with its center over or near the Texas coast for several days. The station figures show rainfall accumulated over eight days. They do not tell how much fell in any specific hour or on any individual day. Source 1 Source 2

A gauge reading and a rainfall map have different scales

A gauge measures the amount at one location. Regional rainfall maps estimate or average totals across areas, so their highest map values can differ from a point measurement. USGS notes the two record drainage-district observations may also have been absent from the measurements used to prepare the regional maps. Source 1

Rainfall depth and river flooding are separate records

Heavy rain feeds runoff across river basins, and different areas reach peak river flows at different times. For its post-flood analysis with FEMA, USGS separately selected 74 streamflow gauges. The 40 sites here measure the rainfall input. The streamflow and inundation records answer where and how the water moved afterward. Source 1

Sources

• USGS Scientific Investigations Report 2018-5070, Hurricane Harvey rainfall and streamflows
• National Hurricane Center tropical cyclone report, Hurricane Harvey