My understanding is that typically a hurricane will lose energy as it travels inland and is deprived of the warm water from the ocean. In Harvey’s case, weather patterns kept it hovering over the Houston area where it could still sustain itself by drawing energy from the Gulf.
I know heavy winds were experienced in Corpus Christi but the big problem in Houston is that incredible amount of rain that never seemed to end.
There are numerous factors involved as far as a given named storm maintaining hurricane strength well inland but it certainly does occur. Houston is fortunate that this stalled storm didn’t draw energy to sustain windspeed in addition to moisture from the gulf.