Statement 1: Wind gaps in the course of a river do not allow the construction of upland roads and railways.

Explanation:
- Wind gaps are narrow passages or valleys in mountain ranges that are formed due to erosion by wind.
- These gaps are typically located in upland areas where rivers have cut through the mountain ranges.
- Due to their narrow and steep nature, wind gaps pose significant challenges for the construction of roads and railways.
- Constructing roads and railways in wind gaps would require extensive engineering efforts and may not be economically or technically feasible.
- The difficult topography, limited space, and high terrain make it challenging to create a stable and safe infrastructure in wind gaps.
- Therefore, it is correct to say that wind gaps in the course of a river do not allow the construction of upland roads and railways.

Statement 2: Deltas are less preferred sites than estuaries for the siting of large ports.

Explanation:
- Deltas are landforms formed at the mouth of a river where it meets a body of water, typically a sea or an ocean.
- Estuaries, on the other hand, are the areas where a river meets the sea and freshwater mixes with saltwater.
- Both deltas and estuaries are potential sites for the siting of large ports due to their proximity to the sea and availability of waterways for navigation.
- However, deltas have certain disadvantages compared to estuaries for port siting.
- Deltas are often characterized by shifting channels, sandbars, and sediment deposition, which can pose challenges for navigation and the maintenance of navigational channels.
- Deltas are also prone to frequent changes in their shape and size due to sedimentation and erosion, which can affect the long-term viability of port infrastructure.
- Estuaries, on the other hand, tend to have more stable and predictable water flows, making them more suitable for large port operations.
- Therefore, it is correct to say that deltas are less preferred sites than estuaries for the siting of large ports.

Conclusion:
- Both Statement 1 and Statement 2 are correct.
- Wind gaps in the course of a river indeed do not allow the construction of upland roads and railways due to their challenging topography.
- Deltas are less preferred sites than estuaries for the siting of large ports due to their dynamic nature and challenges associated with navigation and maintenance.