Estuaries have been used for settlement by humans since 5000-9000 years ago [Day et al., 2012]. The calm environment and nutrient-rich soil encouraged the development of ports and agriculture. Over-development however has put estuaries in unhealthy condition, where the water is polluted (excessive nutrient or salt intrusion problem) and natural morphodynamic equilibrium is disturbed. This implies that the need for effective estuarine management is crucial. Unfortunately, most of the estuaries around the globe are still ungauged, limiting the understanding and knowledge of the underlying hydrological process. Hence, the aims of this study are to: 1) collect and reorganize the existing information available from various sources such as the literature, engineering reports, and open access databases shared by researchers and authorities; 2) conduct field surveys in 7 Malaysian estuaries to expand the database; and 3) develop predictive measures to estimate the two important calibration parameters in salt intrusion (the Van der Burgh and dispersion coefficients), the estuary depth, and the bankfull discharge. Data collection was carried out in 7 previously un-surveyed Malaysian estuaries during the dry season and near spring tide, from June to August 2012 and February to March 2013. Fundamental data such as cross-sectional area, water level, and salinity were surveyed, starting from the estuary mouth moving landward until a few kilometers beyond the salt intrusion limit. Subsequently, the fully analytical 1-D salt intrusion model of Savenije [1986] was tested on all the newly surveyed estuaries making used of the data collected. Here, the geometry was analyzed following a branched exponential function. The cross-sectional data were adjusted in reference to the mean tidal level. The results obtained from the salt intrusion model show that the model is capable of simulating the salinity distribution in comparison to the observed data. Although the existing predictive equations for the Van der Burgh and dispersion coefficients appeared reliable, there were still some issues to deal with. In this study, several modifications were made to improve the predictive equations. Geometry and salinity data of 30 estuaries worldwide including the newly surveyed were collected and re-analysed to create a consistence data base. Selection of data was made to ensure that only the reliable dataset was applied in the derivation of the predictive equations, using various combinations of dimensionless parameters. Moreover, the seaward boundary location was moved to the inflection point (determined by the geometry analysis) where the system becomes tide dominated. Another reason for shifting the boundary location was to eliminate the dilemma of the downstream boundary location. From analyses, it is found that the predictive coefficients are strongly related to the geometry, tidal strength, friction and the Canter-Cremers estuarine number. The new equation obtained for the dispersion is very satisfying and reliable. On the other hand, the correlation for the Van der Burgh coefficient is slightly lower, implying the equation has to be used with caution. Nevertheless, these predictive equations are adequate to be applied for obtaining a first order estimate of the salt intrusion. In cases where data are strictly limited, more parameters have to be predicted. In salt intrusion analysis, discharge data is crucial because the salt intrusion length is strongly dependent on the amount of river flow draining into the estuary. Apart from the discharge, the estuary depth is also an important parameter to determine the salt intrusion. Without an extensive filed survey, it is nearly impossible to obtain these parameters, especially the discharge. In this study, an effort has been made to find predictive measures that can be applied to estimate depth and discharge. This was done by relating the hydraulic geometry theory of river regime [Lacey, 1930] with the estuary depth estimated using the analytical tidal dynamics solutions of Savenije et al. [2008]. Subsequently, the relation was verified by linking the Canter-Cremers estuarine flood number for bankfull discharge at 1.5-years return period to the estuary shape (represented by the width ratio at the infection point and upstream boundary of the tidal limit). Results show that the relationship between the estuary depth and bankfull discharge can be expressed by a power function with an exponent near to 1/3, in agreement with Lacey’s theory. Furthermore, the results obtained from the Canter-Cremers flood number analysis imply that the estuary depth is determined by the bankfull discharge, while the width is determined by the tide. This analysis has demonstrated that the downstream hydraulic geometry theory can also be applied in the estuary region. In spite of the fact that predictive measures established are useful in making first order estimates of salt intrusion, they are still open for improvements. It is hope that in future more reliable data can be collected and used to strengthen the predictive methods.