Jordan Falls River Delta EarthCache

Jordan Falls River Delta

Jordan Falls is located along Highway 103, up the Lake John Road and at exit 24 along the Lockeport Loop to the Town of Lockeport. It is a community of the Municipality of the District of Shelburne in Nova Scotia. Originally occupied by Aboriginal peoples and Acadians, they were replaced by US puritans in lower farmlands in 1700s, then mixed settlers, and then loyalists from the American revolution in 1776.

The Jordan River Trail is located along the abandoned Halifax and Southwestern railway line. The railway carried passengers and freight between Halifax and Yarmouth from 1907-1969. The trail winds through a salt marsh, home to ducks, herons, and other birds. It crosses the Jordan River and ends at the Jordan Branch Road. On a clear day there is a fantastic view from the bridge looking both up the river and out to the ocean. Trees and other plants to look for along the way include speckled alder, wild rose, mountain ash, red maple, birch, tamarack, white pine, and the occasional locust.

Jordan River

The Village on the Jordan River and resulting delta basin and lands are tidal with substantial marshlands that can be visited by trails starting from several points in the village. Jordan River and the river delta feeds into Jordan Bay. Jordan river is an example of a Northern river delta. Jordan river forms a delta along its edges and has an estuary in the lower part of the river.

How a River Delta Forms

Deltas are formed when sediment in the river flows into another body of water and the speed slows allowing the sediment to be deposited. This can occur where the river hits a wider width, a lake or the ocean. These intersections cause the water flow to slow, allowing the large amounts of sediment to drop from the water onto the river bottom. This repeated process results in sediment build up, decreasing the gradient of the river bed and the floor of the river becoming closer to the floodplain. Over time the river channel becomes more unstable and prone to flooding.

With the sediment build up the river will breach it’s banks and flood causing the water flow to find the fastest and easiest route downstream. As the river continues to breach distributaries (veins of the river) form. These distributaries give the delta the distinctive shape. Different types of deltas exist based on how they were formed. A bar of sand, gravel or heavy sediment in the mouth of a river can also cause the water to divert around so over time a forking will occur.

As the river continues to breach more distributaries appear like veins. This gives many delta their distinctive shape even though different types of delta exist, based on how they are formed.

Types Of River Deltas

Deltas can be categorized based on their shape, formation, or location. Four of the most common ways to distinguish delta types are as follows:

Wave-Dominated Deltas

Wave-dominated deltas are created and shaped by the movements of waves within the body of water in question. The waves influence the shape and formation of the river delta by shaping the sedimentary deposits near the river;s mouth. The waves move the deposits from the mouth opening towards the shore, preventing a bar from building up.

Where delta types don't often have many distributary channels or veins, as the flow of the river into the larger body of water is not resisted. The waves also serve as a natural sifting and sorting mechanism because light fine grains are washed away in the waves, while heavy sediments are left behind.

Gilbert Deltas

The Gilbert river delta occurs when coarse sediments are deposited at the river mouth. The term is named after geologist Grove Karl Gilbert, who coined this type of delta. These types of deltas are most commonly formed by mountain rivers which flow into fresh water lakes. The water flow from the mountain tends to carry larger denser sediments which are washed along in the river where they stop, forming blockades at the river mouth.

Estuarine Deltas

River deltas can also be estuarine, which means they are partly fresh water and partly salt water. In these deltas the river does not flow directly into the ocean, or salt water, but rather into an estuary at the river mouth.

Tide-Dominated Deltas

Tide dominated deltas are somewhat similar to wave ones, as the movement of water in the delta helps to form the shape and type of river delta that is created, but the resulting shape is very different. In these cases, the rise and fall of the tide is what has the biggest impact. Tidal deltas often have many distributaries, as well as dendritic structures due to the presence of sandbars and ridges under the water. The changes in the tides can cause certain river branches to become filled or blocked by silt, resulting in the birth of a new distributary. Because of this, these deltas have many many veins and arms, as the constantly moving tide causes the delta to morph often.

It is well known that rivers often carry tremendous amounts of sediment which, when emptied into the oceans, construct distinctive patterns in the underlying sediments. In an estuary, the deposition of sediments is greatly influenced by tidal currents and ocean waves. Even climate is a factor in how the sands and muds settle into distinct patterns. During seasonal storms, erosion is increased and the waters become heavily laden with a wide variety of sediments. Unlike deltas, in which the finer sediments are often carried far out to sea, the estuary is bordered on the deeper ocean side by heavy sands while clays and muds are dropped at river mouths. As tidal forces work the sediments by tumbling and rolling them, the lighter and finer particles are left near the river mouth. The build-up of coarse-grained (larger particle size) sands at the estuary edge often makes a barrier at the outer edge of the estuary that contains the bulk of the fine sediment and diluted water. The sediment structures in these ridges are defined as longitudinal or oblique bars. The structures in the upper reaches of the estuary are described as asymmetric and longitudinal bars become point bars similar to those observed in rivers. A dendritic (tree-shaped) pattern of channels occurs in these finer, flat lying sediments.

Shape Of A River Delta

When categorizing deltas by shape, there are a few common terms.

They include fan or Arcuate (shaped like a bow; curved) deltas which generally have an arch-like shape spreading from the river mouth. A bowed or curved Delta with the convex margin facing the body of water. Relatively coarse sediments are formed in this type of Delta. The river activity is balanced with the wind.

Cuspate deltas occur when a river flows into a stable water body (sea or ocean), and the sediment brought along collides with the waves resulting in an even spreading out of sediment on either side of its channel. Cuspate shaped deltas tend to have more wave-induced arcs that point towards the sea

The Bird’s foot Delta is named because it forms like a bird foot’s claw. This shape is created when the waves are weak and the river flow is stronger. They are formed due to deposition of finer materials by river water. Bird-Foot Deltas which have wider spread distinct distributaries that form the triangular shape of a bird foot; and inverted deltas which appear like ‘backwards’ shaped distributary networks with a dominant stream leading towards the ocean.

An untraditional looking delta is the inverted delta. The distributary network of an inverted delta is inland, while a single stream reaches the ocean or other body of water. Inland deltas, which empty into a plain, are extremely rare.

To log this Earthcache visit the viewing location.  Please answer the following questions and send in a timely manner to my geocaching profile or email. Answers not received will result in deleted logs.

Needs to be done at low tide or you won’t see the delta

Questions:

1. What type of delta is it (Wave, Tidal, Gilbert, Estuarine)?

2. Why did you choose that delta type?

3. How did the delta form?

4. Which shape is the delta (Arcuate, Cuspate, Bird’s foot)?

5. How wide is the delta portion on the west and east sides?

6. How wide is the river?

7. How has the delta affected the width of the river?

8. Post a picture in your log with a personal item or hand in picture to prove you were there.

[REQUIRED] In accordance with the updated guidelines from Geocaching Headquarters published in June 2019, photos are now an acceptable logging requirement and WILL BE REQUIRED TO LOG THIS CACHE. Please provide a photo of yourself or a personal item in the picture to prove you visited the site.