PAVED LAND, RISING WATERS: A VIDEO DOCUMENTARY

Andrew M. Hilburn, Department of Earth Sciences, University of South Alabama, Mobile, AL 36688. E-mail: Buffalo65@aol.com.

Urbanization affects the rainfall runoff and drainage rates of a watershed. Paved surfaces prevent ground penetration thus funneling rain water into a stream more rapidly and in greater amounts. In addition, concreted and channelized streams facilitate the rapid movement of the drainage load. Environmental problems such as littering, sediment runoff, and automobile emissions move easier and faster into the streams of an urbanized watershed. This film documentary covers the process of this rapid drainage during a heavy rainfall while noting the environmental effects such an event can bring to a watershed. The film is shot on analog 8mm film and edited by computer software.

Keyword: film, urbanization, watershed, drainage

Introduction

The topographic dynamics of a watershed change once is it urbanized. The natural forests, fields, and swamps give way to residences, businesses, parking lots, utility networks and roads (Rose and Peters 2001) which lead to physical and environmental changes in the streams that compose the watershed system (Caraco 1999). During a heavy rainfall an urban watershed and its resulting river, receives large amounts of water in a shorter amount of time than would a more rural one (Leopold 1997). Paved surfaces inhibit ground absorption while at the same time assisting drainage and mass runoff. In addition, many streams in cities are engineered by concretion and sloping to move large quantities of runoff in order to prevent flooding thus further expediting and increasing water flow through the watershed (Brookes 1988). Although flood prevention is beneficial, stream channelization and engineering also aid in the transmission of latent pollutants and sedimentary runoff that would normally be absorbed or deposited in or on the ground prior to reaching the stream (Schueler 2000).

The Dog River Watershed, which drains a large part of the city of Mobile, Alabama, is a good example of an urban watershed that receives many high intensity, 10 year rains. Its streams are diverse in size and in the ways and extent in which they have been naturally altered or engineered. Some tributaries have even been created. Mobile, Alabama is one of the wettest metropolitan areas in the United States, averaging 64 inches annually. It receives much of this rain in short-duration, heavy-intensity events (Taylor 1998) which further increase runoff and deposition.

There has been much research on these heavy rainfall events in the Dog River Watershed, ranging from frequency studies to erosion impact. Yet, aside from a few photographs and video stills, nothing exists that visually shows how one of these events and their effects appear in real-life.

Research Question

This project seeks to capture a heavy, intense rainfall event, one that precipitates at least 0.3” of rain per hour, or one of nearly similar intensity in the Dog River Watershed on video. In addition to the rainfall event, the non-meteorological factors that cause such an event will be shown with the after effects of garbage and sediment runoff and deposition.

Methods

This video documentary was shot on 8mm analog tape on a Sony CCD- TR91 video camcorder during the months of March through April, 2003. Footage of the event was shot whenever a medium to large intensity rain occurred, during both night and daytime. Additional footage was filmed during non-rainy conditions in order to show contrast and for scenes indirectly pertaining to the event, such as before and after sequences, post rainfall drainage, and definitive scenes. Additional graphs and visual aids were used to show abstract concepts relevant to the theme of the movie. I created a video log describing the counter time, scene description, shot quality and usability of the scene (Table 1). From this log, I created a rough storyboard that I casually jotted on paper due to its constantly changing chronology and scene selection (Harwood 1982). After all filming, I edited the stock by computer. The software and hardware interface used in production were the Pinnacle Studio 8 and its AV/DV driver. The final video was compressed into MPEG-1 format and saved on a CD-R.

Table 1. Excerpt from video log.

Video Log		Tape 1
Counter Start	Counter End	Description	Date	Quality (0-3)	Use?
00:00	00:33	Eslava Crk., Pan, Sunny	16-Mar	2.5	Y
00:34	00:50	Eslava Crk., under bridge	16-Mar	2.5	Y
00:51	01:02	Eslava Crk. UB, rev.	16-Mar	1.5	N
01:05	02:00	Eslava Crk. Big Lots PL	16-Mar	2	M
02:01	02:38	H. Aaron Stad.	16-Mar	2	M
02:39	02:56	Tree Shot, Drain ditch	16-Mar	1.5	N
02:59	03:04	Flower	16-Mar	2.5	N
03:04	03:25	Swamp w/ gabions	16-Mar	2.25	M
03:26	03:50	Swamp w/ gabions 2	16-Mar	2.5	M
03:51	04:24	Swamp w/ gabions 3	16-Mar	2.25	M
04:24	04:33	Swamp drain/fall	16-Mar	2	N

Results

There were no true high intensity rainfall events during the course of this project. However, there were three medium sized rains that provided me with enough footage to compile a five-minute long shot.

Discussion

Knowledge of one’s local environment is indeed important. Awareness of relevant and pressing issues pertaining to the environment should be increased and spread around to better inform residents of their impact on the river along with its current state.

The citizens of Mobile, living the rainiest city in the contiguous 48 states, have a vested interest in rainfall management to prevent flooding. Yet, at the same time, it is also important to Mobilians that their city’s main drainage basin, the Dog River Watershed, remains in a good state for reasons ranging from recreation to the health of nearby residents.

The phenomenon of a 10-year rain or other high intensity precipitation has deep impacts into the healthy condition of the Dog River Watershed. Engineered streams allow these heavy rains to bring in loads of litter and sediment into Dog River causing the need for expensive dredging and trash pickup or worse, leaving sediment and litter behind permanently. All of these factors influence the quality of life of the surrounding residents.

The Dog River Watershed’s streams and creeks have been altered to such an extent that they basically function as huge drainage ditches, funneling runoff into Dog River as fast as possible, leaving no water and vegetation behind. Even though stream engineering lowers aesthetic quality and certain ecosystems become lost with stream engineering, it does reduce flood risk (Brookes 1988).

Video media is one of the best ways by which to educate the public. An eye-catching documentary both informs while it entertains, leaving a lasting impact upon the viewing audience, especially one about a local issue.

Conclusion

It is generally agreed upon that most video references used today pertaining to water quality or other enviro-geographical themes seem antiquated with non-contemporary subjects. Their impact and relevance also seem to be limited to a certain region. For example, a film using strip mining as an example of a pollution source probably will not have the same impact in Mobile because there are no strip mines for hundreds of miles. A film documentary such as this one functions best by showing visual evidence of something that is already known and needs a high quality, powerful visual aid to show the magnitude of an event like a 10 year rain in a recognizable locale.

Since this film covers the Dog River Watershed, its prospective audience, which includes Mobile area students, teachers, and environmentally conscious individuals, can more easily relate to the film and possibly retain its message better. As previously implied, the Dog River Clearwater Revival or any other environmental protection group could use this film as a teaching tool for workshops or school expositions.

As a greenhorn in short film production, this project, to say the least, was a learning process. For a field work project, it was a little too ambitious, mostly because of lack of equipment and the time constraints of one semester. Also, as mentioned before, there were no significant rainfalls during this course of study.

Note: Andy's video is still experiencing "technical difficulties.

References

Brookes, A. 1988. Channelized Rivers: Perspectives for Environments Management. Chichester: John Wiley and Sons.

Caraco, D. Dynamics of Urban Stream Channel Enlargement. Watershed Protection Techniques 3 (3): 729-734.

Leopold, L.B. 1997. Waters, Rivers, and Creeks. Sausalito, CA: University Science Books.

Rose, S. and N.E. Peters. 2001. Effects of urbanization on streamflow in the Atlanta area (Georgia, USA): a comparative hydrological approach. Hydrological Processes 15: 1441 – 1457.

Schueler, T.R.. Why stormwater matters. In The Practice of Watershed Protection. Schueler, T.R. 2000. pp. 365-370. Ellicott City, MD: Center for Watershed Protection.