What was the storm surge height from Hurricane Harvey?
For a general view of the surge in the region, the maps in u-surge give a pretty good idea of numbers and more affected regions.

The USGS provides a comprehensive view of High Water Marks (HWM) in the entire region. If you are looking for observations, then the HWM database gives you the best spatial coverage. While HWM do not provide surge information per se as it includes multiple processes (like ocean surge from the storm, waves and wave run-up, and flooding from rivers and precipitation), it gives an idea of the extreme values of water level in many locations. It also shows the large spatial variability of the effects of the storm. There are also tide gauge and rapid response stations in the area as part of the USGS database that provides more information of the temporal evolution of water levels. 

Part of the problem is that storm surge is only the result of two processes: 1) wind piling water against the coast and 2) low atmospheric pressure that causes ocean level to go up. Additionally, you have many other processes affecting water levels during a storm or hurricane. The tides are still there as always and that adds complications because if the storm surge peak occurs during high tide, then the impacts are much worse. Tides in the Gulf of Mexico are not that high, but they can be a much larger factors in some other areas. The combination of storm surge and astronomical tides is often label "storm tide", which is a very poor name choice and leads to much confusion, as clearly the storm does not cause a tide. Another impact is that associated with the high winds, you have large wave heights. As these high waves approach the coast, they cause higher water levels as a result of wave run-up and wave setup. The magnitude of these wave effects can be pretty large in some locations especially in ocean-facing locations. The last main impact on water level is precipitation and the resulting increase river discharge. Clearly, Harvey had a catastrophic amount of precipitation and its impacts were much larger than the purely oceanic-driven storm surge in this storm.

Many agencies are working on developing a measure of water level that includes all these processes. For instance a good example is the USGS effort to develop Total Water Level measurements and forecast.