Aravinda, the answer to your question would vary quite dramatically depending on the region you are talking about. Generally, species with higher water requirements or flood tolerances are found near streams. In my area, we see a lot of Salix and Poplar in the riparian zone as well as Equisetum. But this would vary depending on your region. A quick search for "Riparian Vegetation of Sri Lanka" brought up this essay on the subject http://dlib.pdn.ac.lk/bitstream/1/3721/1/S.N.%20Wickramaratne%20-%202005.pdf

Riparian vegetation differs from region to region. Please follow the following links and pdf attachments.

https://www.researchgate.net/publication/40732105_Riparian_vegetation_assessment_of_Cauvery_River_Basin_of_South_India

http://link.springer.com/article/10.1007/s11629-009-2080-5

Article Riparian vegetation assessment of Cauvery River Basin of South India

Please follow these researchgate links also.

https://www.researchgate.net/publication/289166644_Riparian_vegetation_of_Mini_River_in_Vadodara_Gujarat

https://www.researchgate.net/publication/47552962_Studies_on_riverine_flora_of_Pamba_river_basin_Kerala

https://www.researchgate.net/publication/283347573_Riparian_Flora_of_Mahi_River_Gujarat

https://www.researchgate.net/publication/260703396_Connectivity_processes_and_riparian_vegetation_of_the_upper_Parana_River_Brazil

Article Riparian vegetation of Mini River in Vadodara, Gujarat

Article Studies on riverine flora of Pamba river basin, Kerala

Article Riparian Flora of Mahi River, Gujarat

Article Connectivity processes and riparian vegetation of the upper ...

Riparian vegetation vary from place to place. Tolerance of plants to flood and other soil conditions along with variations in temperature / altitude may affect the diversity of the species. I also agree with the commends of the above authors.

Please go through this pdf attachment also for said query.

Go through this report, it may useful 

http://www.cds.ac.in/krpcds/report/amita.pdf

Hello friend

       As others pointed out there are many examples for different site condition. So if you could specify your climatic condition. It may  be helpful to provide a better examples.

have a good day

Kindly refer this particular article

Disturbances and species distribution of the riparian vegetation of a Rift Valley stream

Jude M. Mathooko2,* andSamuel T. Kariuki

African Journal of Ecology

Volume 38, Issue 2, pages 123–129, June 2000

Which has listed Riparian species such as Acacia species found in Africa, among other species. 

Regards

Rajashekar Tummala

I agree with all the recommendations you have received. We can help more if you tell us what do you need the information for.

Hello all,

For a good review article that can provide a nice list of references about studies performed in regions of Mediterranean climate, try this one: https://www.researchgate.net/publication/257569372_Riparian_vegetation_research_in_Mediterranean-climate_regions_Common_patterns_ecological_processes_and_consideration_for_management.

Regards,

Pedro A.

Article Riparian vegetation research in Mediterranean-climate region...

Dear friend, I am posting this paper to you to suggest a method of study, from an example in Greece:

https://www.researchgate.net/publication/200829077_Riparian_woodland_flora_in_upland_rivers_of_Western_Greece

There are many interesting approaches. Also please read the wonder book by Naiman et al. - it is required reading for all naturalists who want to know how to study riparian zones:

http://store.elsevier.com/Riparia/Robert-Naiman/isbn-9780126633153/

All the best, 

Stam

Article Riparian woodland flora in upland rivers of Western Greece

Dear Aravinda,

Please check the following links.

Regards

SM Najim

http://www.sijbs.com/index.html/assets/2016/191-197.pdf

http://onlinelibrary.wiley.com/doi/10.1002/ece3.2249/pdf

http://onlinelibrary.wiley.com/doi/10.1002/2015WR018490/abstract

http://file.scirp.org/pdf/OJF_2016090515365315.pdf

Dear Aravinda Bellanthudawa 

Important information about your subject can be found at the following link

https://en.wikipedia.org/wiki/Riparian_zone

GOOD LUCK