"Descriptive essay" is a tricky term, because "essay" means "to try"; that is, the essay form seeks to persuade or convince based on gathered evidence and rhetoric, while "to describe" does not appear on the surface to be argumentative. But a descriptive essay is one which organizes observations into categories. Examples are : high school experiences (which can then be broken down into education, social, sexual, career choices, future goals, or something like that); advertising (media, target audience, measurement of effectiveness, etc.); conservation efforts (recycling, biodegradable substances, farm waste, etc.); astrophysics (astronomy, measuring techniques, probabilities of life, mathematics of mass and energy, etc.); world events (border conflicts, religious influences on government, economies, hegemonies, ethnic problems, etc.); toys (kinds, history, age appropriateness, tie-ins to movies, etc.) Each of these categories are simply examples of areas of description--the real challenge of the descriptive essay is taxonomy and expression of the areas of inquiry.
Since your question states it is about research and asks for topic ideas for "a descriptive research", I will assume that you need to choose a topic for a research study rather than write a descriptive essay. Of course a descriptive essay is part of what you would write to report your findings; however, you ask for topic ideas. A descriptive research is a type of quantitative research. Its purpose is to find information about the phenomena, conditions or variables surrounding a topic. Some primary methods used in descriptive research are case-study, correlational and survey methods. Knowing this, look to current controversial trends in society as possible topics. Possibilities include:
The harmful impact of the typical American diet.
The number of Americans that recycle on a regular basis.
The amount of time students use on social media.
The average college debt of undergraduate and graduate students.
How many public schools have cut arts programs.
How often do high school athletes succeed in college programs.
How healthy is the average public school lunch.
The number of low socioeconomic students that fail state standardized testing.
Descriptive research is used to describe a population or characteristics being studied. This is less of an essay and more like a research topic. You could have as your topic people's views of the 2016 presidential election. You can gather your research by creating a questionnaire and a sample population to poll. If education is more to your interest, you could see if there is a correlation of the amount of education a person has to their current income. You could also poll people about their health, diet, sleep habits and see if that has any bearing on days they miss from work due to illness. One popular study done in the last few years has been for people to record how many hours per day they spend on social media and then compare that to their current level of happiness, which they rank on a scale of 1-10. For your final research topic, you could look at how different fertilizers affect houseplants, but this would require a control and a variable and would not use the polls used in the above studies. I would ask my instructor about how he/she would like the research to be completed.