On the issue of determining the estimated navigable level on inland waterways

This paper examines the issue of determining a reliable estimated navigable level (ENL) for inland waterways of regional significance. The accurate determination of the actual ENL on the inland waterways of the Russian Federation is directly linked to ensuring navigation safety. The ENL establishes a regulatory parameter essential for navigators, enabling the safe transit of vessels through movable or fixed navigable bridge spans, and the vertical clearance of such spans is established on the basis of the ENL. An incorrect determination of the lower boundary of the ENL may result in either a reduction or an increase in the actual vertical clearance: in the former case, certain vessels may be denied passage through movable or fixed navigable bridge spans; in the latter case, if the actual vertical clearance is lower than the prescribed value, a navigational accident may occur during vessel transit within the bridge span. The precise determination of the ENL is particularly important for waterways of regional significance, some of which are located within large urban areas with developed river and canal systems supporting regular navigation. Within the city limits of St. Petersburg, for example, there are 66 bridges with navigable spans permitting vessel transit, and vessels passing through these spans frequently operate with minimal vertical clearance margins; therefore, it is essential to determine the ENL accurately for each individual bridge. Only such an approach ensures the required level of navigation safety while maintaining an adequate level of waterway operational efficiency through the operation of vessels with maximum permissible dimensions on regional waterways where bridges with navigable spans are located.